Android 技術揭秘之滑動移除Activity


一、SwipeBackLayout :

package com.base.view.view.swipeback;

import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import com.base.view.R;

import java.util.ArrayList;
import java.util.List;

/**
* Author: walid ( copy to githup)
* Date : 2016/03/21 18:00
*/
public class SwipeBackLayout extends FrameLayout {
/**
* Minimum velocity that will be detected as a fling
*/
private static final int MIN_FLING_VELOCITY = 400;

private static final int DEFAULT_SCRIM_COLOR = 0x99000000;

private static final int FULL_ALPHA = 255;

/**
* Edge flag indicating that the left edge should be affected.
*/
public static final int EDGE_LEFT = ViewDragHelper.EDGE_LEFT;

/**
* Edge flag indicating that the right edge should be affected.
*/
public static final int EDGE_RIGHT = ViewDragHelper.EDGE_RIGHT;

/**
* Edge flag indicating that the bottom edge should be affected.
*/
public static final int EDGE_BOTTOM = ViewDragHelper.EDGE_BOTTOM;

/**
* Edge flag set indicating all edges should be affected.
*/
public static final int EDGE_ALL = EDGE_LEFT | EDGE_RIGHT | EDGE_BOTTOM;

/**
* A view is not currently being dragged or animating as a result of a
* fling/snap.
*/
public static final int STATE_IDLE = ViewDragHelper.STATE_IDLE;

/**
* A view is currently being dragged. The position is currently changing as
* a result of user input or simulated user input.
*/
public static final int STATE_DRAGGING = ViewDragHelper.STATE_DRAGGING;

/**
* A view is currently settling into place as a result of a fling or
* predefined non-interactive motion.
*/
public static final int STATE_SETTLING = ViewDragHelper.STATE_SETTLING;

/**
* Default threshold of scroll
*/
private static final float DEFAULT_SCROLL_THRESHOLD = 0.3f;

private static final int OVERSCROLL_DISTANCE = 10;

private static final int[] EDGE_FLAGS = {
EDGE_LEFT, EDGE_RIGHT, EDGE_BOTTOM, EDGE_ALL
};

private int mEdgeFlag;

/**
* Threshold of scroll, we will close the activity, when scrollPercent over
* this value;
*/
private float mScrollThreshold = DEFAULT_SCROLL_THRESHOLD;

private Activity activity;
private boolean enable = true;
private View contentView;
private ViewDragHelper dragHelper;
private float scrollPercent;
private int contentLeft;
private int contentTop;

/**
* The set of listeners to be sent events through.
*/
private List<SwipeListener> listeners;

private Drawable shadowLeft;
private Drawable shadowRight;
private Drawable shadowBottom;

private float scrimOpacity;

private int scrimColor = DEFAULT_SCRIM_COLOR;

private boolean inLayout;
private Rect tmpRect = new Rect();
/**
* Edge being dragged
*/
private int trackingEdge;

public SwipeBackLayout(Context context) {
this(context, null);
}

public SwipeBackLayout(Context context, AttributeSet attrs) {
this(context, attrs, R.attr.SwipeBackLayoutStyle);
}

public SwipeBackLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs);
dragHelper = ViewDragHelper.create(this, new ViewDragCallback());
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.SwipeBackLayout);
int edgeSize = a.getDimensionPixelSize(R.styleable.SwipeBackLayout_edge_size, -1);
if (edgeSize > 0) { setEdgeSize(edgeSize); }
int mode = EDGE_FLAGS[a.getInt(R.styleable.SwipeBackLayout_edge_flag, 0)];
setEdgeTrackingEnabled(mode);
int shadowLeft = a.getResourceId(R.styleable.SwipeBackLayout_shadow_left, R.drawable.ic_shadow_left);
int shadowRight = a.getResourceId(R.styleable.SwipeBackLayout_shadow_right, R.drawable.ic_shadow_right);
int shadowBottom = a.getResourceId(R.styleable.SwipeBackLayout_shadow_bottom, R.drawable.ic_shadow_bottom);
setShadow(shadowLeft, EDGE_LEFT);
setShadow(shadowRight, EDGE_RIGHT);
setShadow(shadowBottom, EDGE_BOTTOM);
a.recycle();
final float density = getResources().getDisplayMetrics().density;
final float minVel = MIN_FLING_VELOCITY * density;
dragHelper.setMinVelocity(minVel);
dragHelper.setMaxVelocity(minVel * 2f);
}

/**
* Sets the sensitivity of the NavigationLayout.
*
* @param context The application context.
* @param sensitivity value between 0 and 1, the final value for touchSlop =
* ViewConfiguration.getScaledTouchSlop * (1 / s);
*/
public void setSensitivity(Context context, float sensitivity) {
dragHelper.setSensitivity(context, sensitivity);
}

/**
* Set up contentView which will be moved by user gesture
*/
private void setContentView(View view) {
contentView = view;
}

public void setEnableGesture(boolean enable) {
this.enable = enable;
}

/**
* Enable edge tracking for the selected edges of the parent view. The
* callback's
* {@link me.imid.swipebacklayout.lib.ViewDragHelper.Callback#onEdgeTouched(int, int)}
* and
* {@link me.imid.swipebacklayout.lib.ViewDragHelper.Callback#onEdgeDragStarted(int, int)}
* methods will only be invoked for edges for which edge tracking has been
* enabled.
*
* @param edgeFlags Combination of edge flags describing the edges to watch
* @see #EDGE_LEFT
* @see #EDGE_RIGHT
* @see #EDGE_BOTTOM
*/
public void setEdgeTrackingEnabled(int edgeFlags) {
mEdgeFlag = edgeFlags;
dragHelper.setEdgeTrackingEnabled(mEdgeFlag);
}

/**
* Set a color to use for the scrim that obscures primary content while a
* drawer is open.
*
* @param color Color to use in 0xAARRGGBB format.
*/
public void setScrimColor(int color) {
scrimColor = color;
invalidate();
}

/**
* Set the size of an edge. This is the range in pixels along the edges of
* this view that will actively detect edge touches or drags if edge
* tracking is enabled.
*
* @param size The size of an edge in pixels
*/
public void setEdgeSize(int size) {
dragHelper.setEdgeSize(size);
}

/**
* Add a callback to be invoked when a swipe event is sent to this view.
*
* @param listener the swipe listener to attach to this view
*/
public void addSwipeListener(SwipeListener listener) {
if (listeners == null) {
listeners = new ArrayList<>();
}
listeners.add(listener);
}

/**
* Removes a listener from the set of listeners
*
* @param listener
*/
public void removeSwipeListener(SwipeListener listener) {
if (listeners == null) {
return;
}
listeners.remove(listener);
}

public interface SwipeListener {
/**
* Invoke when state change
*
* @param state flag to describe scroll state
* @param scrollPercent scroll percent of this view
* @see #STATE_IDLE
* @see #STATE_DRAGGING
* @see #STATE_SETTLING
*/
void onScrollStateChange(int state, float scrollPercent);

/**
* Invoke when edge touched
*
* @param edgeFlag edge flag describing the edge being touched
* @see #EDGE_LEFT
* @see #EDGE_RIGHT
* @see #EDGE_BOTTOM
*/
void onEdgeTouch(int edgeFlag);

/**
* Invoke when scroll percent over the threshold for the first time
*/
void onScrollOverThreshold();
}

/**
* Set scroll threshold, we will close the activity, when scrollPercent over
* this value
*
* @param threshold
*/
public void setScrollThresHold(float threshold) {
if (threshold >= 1.0f || threshold <= 0) {
throw new IllegalArgumentException("Threshold value should be between 0 and 1.0");
}
mScrollThreshold = threshold;
}

/**
* Set a drawable used for edge shadow.
*
* @param shadow Drawable to use
* @param edgeFlags Combination of edge flags describing the edge to set
* @see #EDGE_LEFT
* @see #EDGE_RIGHT
* @see #EDGE_BOTTOM
*/
public void setShadow(Drawable shadow, int edgeFlag) {
if ((edgeFlag & EDGE_LEFT) != 0) {
shadowLeft = shadow;
} else if ((edgeFlag & EDGE_RIGHT) != 0) {
shadowRight = shadow;
} else if ((edgeFlag & EDGE_BOTTOM) != 0) {
shadowBottom = shadow;
}
invalidate();
}

/**
* Set a drawable used for edge shadow.
*
* @param resId Resource of drawable to use
* @param edgeFlags Combination of edge flags describing the edge to set
* @see #EDGE_LEFT
* @see #EDGE_RIGHT
* @see #EDGE_BOTTOM
*/
public void setShadow(int resId, int edgeFlag) {
setShadow(getResources().getDrawable(resId), edgeFlag);
}

/**
* Scroll out contentView and finish the activity
*/
public void scrollToFinishActivity() {
final int childWidth = contentView.getWidth();
final int childHeight = contentView.getHeight();

int left = 0, top = 0;
if ((mEdgeFlag & EDGE_LEFT) != 0) {
left = childWidth + shadowLeft.getIntrinsicWidth() + OVERSCROLL_DISTANCE;
trackingEdge = EDGE_LEFT;
} else if ((mEdgeFlag & EDGE_RIGHT) != 0) {
left = -childWidth - shadowRight.getIntrinsicWidth() - OVERSCROLL_DISTANCE;
trackingEdge = EDGE_RIGHT;
} else if ((mEdgeFlag & EDGE_BOTTOM) != 0) {
top = -childHeight - shadowBottom.getIntrinsicHeight() - OVERSCROLL_DISTANCE;
trackingEdge = EDGE_BOTTOM;
}

dragHelper.smoothSlideViewTo(contentView, left, top);
invalidate();
}

@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
if (!enable) {
return false;
}
try {
return dragHelper.shouldInterceptTouchEvent(event);
} catch (ArrayIndexOutOfBoundsException e) {
// FIXME: handle exception
// issues #9
return false;
}
}

@Override
public boolean onTouchEvent(MotionEvent event) {
if (!enable) {
return false;
}
dragHelper.processTouchEvent(event);
return true;
}

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
inLayout = true;
if (contentView != null) {
contentView.layout(contentLeft, contentTop,
contentLeft + contentView.getMeasuredWidth(),
contentTop + contentView.getMeasuredHeight());
}
inLayout = false;
}

@Override
public void requestLayout() {
if (!inLayout) {
super.requestLayout();
}
}

@Override
protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
final boolean drawContent = child == contentView;

boolean ret = super.drawChild(canvas, child, drawingTime);
if (scrimOpacity > 0 && drawContent
&& dragHelper.getViewDragState() != ViewDragHelper.STATE_IDLE) {
drawShadow(canvas, child);
drawScrim(canvas, child);
}
return ret;
}

private void drawScrim(Canvas canvas, View child) {
final int baseAlpha = (scrimColor & 0xff000000) >>> 24;
final int alpha = (int) (baseAlpha * scrimOpacity);
final int color = alpha << 24 | (scrimColor & 0xffffff);

if ((trackingEdge & EDGE_LEFT) != 0) {
canvas.clipRect(0, 0, child.getLeft(), getHeight());
} else if ((trackingEdge & EDGE_RIGHT) != 0) {
canvas.clipRect(child.getRight(), 0, getRight(), getHeight());
} else if ((trackingEdge & EDGE_BOTTOM) != 0) {
canvas.clipRect(child.getLeft(), child.getBottom(), getRight(), getHeight());
}
canvas.drawColor(color);
}

private void drawShadow(Canvas canvas, View child) {
final Rect childRect = tmpRect;
child.getHitRect(childRect);

if ((mEdgeFlag & EDGE_LEFT) != 0) {
shadowLeft.setBounds(childRect.left - shadowLeft.getIntrinsicWidth(), childRect.top,
childRect.left, childRect.bottom);
shadowLeft.setAlpha((int) (scrimOpacity * FULL_ALPHA));
shadowLeft.draw(canvas);
}

if ((mEdgeFlag & EDGE_RIGHT) != 0) {
shadowRight.setBounds(childRect.right, childRect.top,
childRect.right + shadowRight.getIntrinsicWidth(), childRect.bottom);
shadowRight.setAlpha((int) (scrimOpacity * FULL_ALPHA));
shadowRight.draw(canvas);
}

if ((mEdgeFlag & EDGE_BOTTOM) != 0) {
shadowBottom.setBounds(childRect.left, childRect.bottom, childRect.right,
childRect.bottom + shadowBottom.getIntrinsicHeight());
shadowBottom.setAlpha((int) (scrimOpacity * FULL_ALPHA));
shadowBottom.draw(canvas);
}
}

public void attachToActivity(Activity activity) {
this.activity = activity;
TypedArray a = activity.getTheme().obtainStyledAttributes(new int[]{
android.R.attr.windowBackground
});
int background = a.getResourceId(0, 0);
a.recycle();

ViewGroup decor = (ViewGroup) activity.getWindow().getDecorView();
ViewGroup decorChild = (ViewGroup) decor.getChildAt(0);
decorChild.setBackgroundResource(background);
decor.removeView(decorChild);
addView(decorChild);
setContentView(decorChild);
decor.addView(this);
}

@Override
public void computeScroll() {
scrimOpacity = 1 - scrollPercent;
if (dragHelper.continueSettling(true)) {
ViewCompat.postInvalidateOnAnimation(this);
}
}

private class ViewDragCallback extends ViewDragHelper.Callback {
private boolean mIsScrollOverValid;

@Override
public boolean tryCaptureView(View view, int i) {
boolean ret = dragHelper.isEdgeTouched(mEdgeFlag, i);
if (ret) {
if (dragHelper.isEdgeTouched(EDGE_LEFT, i)) {
trackingEdge = EDGE_LEFT;
} else if (dragHelper.isEdgeTouched(EDGE_RIGHT, i)) {
trackingEdge = EDGE_RIGHT;
} else if (dragHelper.isEdgeTouched(EDGE_BOTTOM, i)) {
trackingEdge = EDGE_BOTTOM;
}
if (listeners != null && !listeners.isEmpty()) {
for (SwipeListener listener : listeners) {
listener.onEdgeTouch(trackingEdge);
}
}
mIsScrollOverValid = true;
}
boolean directionCheck = false;
if (mEdgeFlag == EDGE_LEFT || mEdgeFlag == EDGE_RIGHT) {
directionCheck = !dragHelper.checkTouchSlop(ViewDragHelper.DIRECTION_VERTICAL, i);
} else if (mEdgeFlag == EDGE_BOTTOM) {
directionCheck = !dragHelper
.checkTouchSlop(ViewDragHelper.DIRECTION_HORIZONTAL, i);
} else if (mEdgeFlag == EDGE_ALL) {
directionCheck = true;
}
return ret & directionCheck;
}

@Override
public int getViewHorizontalDragRange(View child) {
return mEdgeFlag & (EDGE_LEFT | EDGE_RIGHT);
}

@Override
public int getViewVerticalDragRange(View child) {
return mEdgeFlag & EDGE_BOTTOM;
}

@Override
public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
super.onViewPositionChanged(changedView, left, top, dx, dy);
if ((trackingEdge & EDGE_LEFT) != 0) {
scrollPercent = Math.abs((float) left
/ (contentView.getWidth() + shadowLeft.getIntrinsicWidth()));
} else if ((trackingEdge & EDGE_RIGHT) != 0) {
scrollPercent = Math.abs((float) left
/ (contentView.getWidth() + shadowRight.getIntrinsicWidth()));
} else if ((trackingEdge & EDGE_BOTTOM) != 0) {
scrollPercent = Math.abs((float) top
/ (contentView.getHeight() + shadowBottom.getIntrinsicHeight()));
}
contentLeft = left;
contentTop = top;
invalidate();
if (scrollPercent < mScrollThreshold && !mIsScrollOverValid) {
mIsScrollOverValid = true;
}
if (listeners != null && !listeners.isEmpty()
&& dragHelper.getViewDragState() == STATE_DRAGGING
&& scrollPercent >= mScrollThreshold && mIsScrollOverValid) {
mIsScrollOverValid = false;
for (SwipeListener listener : listeners) {
listener.onScrollOverThreshold();
}
}

if (scrollPercent >= 1) {
if (!activity.isFinishing()) {
activity.finish();
activity.overridePendingTransition(0, 0);
}
}
}

@Override
public void onViewReleased(View releasedChild, float xvel, float yvel) {
final int childWidth = releasedChild.getWidth();
final int childHeight = releasedChild.getHeight();
int left = 0, top = 0;
if ((trackingEdge & EDGE_LEFT) != 0) {
left = xvel > 0 || xvel == 0 && scrollPercent > mScrollThreshold ?
childWidth + shadowLeft.getIntrinsicWidth() + OVERSCROLL_DISTANCE : 0;
} else if ((trackingEdge & EDGE_RIGHT) != 0) {
left = xvel < 0 || xvel == 0 && scrollPercent > mScrollThreshold ?
-(childWidth + shadowLeft.getIntrinsicWidth() + OVERSCROLL_DISTANCE) : 0;
} else if ((trackingEdge & EDGE_BOTTOM) != 0) {
top = yvel < 0 || yvel == 0 && scrollPercent > mScrollThreshold ?
-(childHeight + shadowBottom.getIntrinsicHeight() + OVERSCROLL_DISTANCE) : 0;
}
dragHelper.settleCapturedViewAt(left, top);
invalidate();
}

@Override
public int clampViewPositionHorizontal(View child, int left, int dx) {
int ret = 0;
if ((trackingEdge & EDGE_LEFT) != 0) {
ret = Math.min(child.getWidth(), Math.max(left, 0));
} else if ((trackingEdge & EDGE_RIGHT) != 0) {
ret = Math.min(0, Math.max(left, -child.getWidth()));
}
return ret;
}

@Override
public int clampViewPositionVertical(View child, int top, int dy) {
int ret = 0;
if ((trackingEdge & EDGE_BOTTOM) != 0) {
ret = Math.min(0, Math.max(top, -child.getHeight()));
}
return ret;
}

@Override
public void onViewDragStateChanged(int state) {
super.onViewDragStateChanged(state);
if (listeners != null && !listeners.isEmpty()) {
for (SwipeListener listener : listeners) {
listener.onScrollStateChange(state, scrollPercent);
}
}
}
}
}

二、SwipeBackActivityHelper:

package com.base.view.view.swipeback;import android.app.Activity;import android.app.ActivityOptions;import android.graphics.Color;import android.graphics.drawable.ColorDrawable;import android.os.Build;import android.view.LayoutInflater;import android.view.View;import com.base.view.R;import java.lang.reflect.Method;/** * Author: walid ( copy to githup) * Date : 2016/03/21 18:00 */public class SwipeBackActivityHelper {private Activity activity;private SwipeBackLayout swipeBackLayout;public SwipeBackActivityHelper(Activity activity) {this.activity = activity;}public void onActivityCreate() {activity.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));activity.getWindow().getDecorView().setBackgroundDrawable(null);swipeBackLayout = (SwipeBackLayout) LayoutInflater.from(activity).inflate(R.layout.widget_swipeback_layout, null);swipeBackLayout.addSwipeListener(new SwipeBackLayout.SwipeListener() {@Overridepublic void onScrollStateChange(int state, float scrollPercent) {}@Overridepublic void onEdgeTouch(int edgeFlag) {convertActivityToTranslucent(activity);}@Overridepublic void onScrollOverThreshold() {}});}public void onPostCreate() {swipeBackLayout.attachToActivity(activity);}public View findViewById(int id) {if (swipeBackLayout != null) {return swipeBackLayout.findViewById(id);}return null;}public SwipeBackLayout getSwipeBackLayout() {return swipeBackLayout;}/** * Convert a translucent themed Activity * {@link android.R.attr#windowIsTranslucent} to a fullscreen opaque * Activity. * <p/> * Call this whenever the background of a translucent Activity has changed * to become opaque. Doing so will allow the {@link android.view.Surface} of * the Activity behind to be released. * <p/> * This call has no effect on non-translucent activities or on activities * with the {@link android.R.attr#windowIsFloating} attribute. */public static void convertActivityFromTranslucent(Activity activity) {try {Method method = Activity.class.getDeclaredMethod("convertFromTranslucent");method.setAccessible(true);method.invoke(activity);} catch (Throwable ignored) {}}/** * Convert a translucent themed Activity * {@link android.R.attr#windowIsTranslucent} back from opaque to * translucent following a call to * {@link #convertActivityFromTranslucent(Activity)} . * <p/> * Calling this allows the Activity behind this one to be seen again. Once * all such Activities have been redrawn * <p/> * This call has no effect on non-translucent activities or on activities * with the {@link android.R.attr#windowIsFloating} attribute. */public static void convertActivityToTranslucent(Activity activity) {if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {convertActivityToTranslucentAfterL(activity);} else {convertActivityToTranslucentBeforeL(activity);}}/** * Calling the convertToTranslucent method on platforms before Android 5.0 */public static void convertActivityToTranslucentBeforeL(Activity activity) {try {Class<?>[] classes = Activity.class.getDeclaredClasses();Class<?> translucentConversionListenerClazz = null;for (Class clazz : classes) {if (clazz.getSimpleName().contains("TranslucentConversionListener")) {translucentConversionListenerClazz = clazz;}}Method method = Activity.class.getDeclaredMethod("convertToTranslucent",                                                 translucentConversionListenerClazz);method.setAccessible(true);method.invoke(activity, new Object[]{null});} catch (Throwable ignored) {}}/** * Calling the convertToTranslucent method on platforms after Android 5.0 */private static void convertActivityToTranslucentAfterL(Activity activity) {try {Method getActivityOptions = Activity.class.getDeclaredMethod("getActivityOptions");getActivityOptions.setAccessible(true);Object options = getActivityOptions.invoke(activity);Class<?>[] classes = Activity.class.getDeclaredClasses();Class<?> translucentConversionListenerClazz = null;for (Class clazz : classes) {if (clazz.getSimpleName().contains("TranslucentConversionListener")) {translucentConversionListenerClazz = clazz;}}Method convertToTranslucent = Activity.class.getDeclaredMethod("convertToTranslucent",                                                               translucentConversionListenerClazz, ActivityOptions.class);convertToTranslucent.setAccessible(true);convertToTranslucent.invoke(activity, null, options);} catch (Throwable ignored) {}}}

三、ViewDragHelper:

package com.base.view.view.swipeback;import android.content.Context;import android.support.v4.view.MotionEventCompat;import android.support.v4.view.VelocityTrackerCompat;import android.support.v4.view.ViewCompat;import android.support.v4.widget.ScrollerCompat;import android.view.*;import android.view.animation.Interpolator;import java.util.Arrays;/** * Author: walid ( copy to githup) * Date : 2016/03/21 18:00 */public class ViewDragHelper {/** * A null/invalid pointer ID. */public static final int INVALID_POINTER = -1;/** * A view is not currently being dragged or animating as a result of a * fling/snap. */public static final int STATE_IDLE = 0;/** * A view is currently being dragged. The position is currently changing as * a result of user input or simulated user input. */public static final int STATE_DRAGGING = 1;/** * A view is currently settling into place as a result of a fling or * predefined non-interactive motion. */public static final int STATE_SETTLING = 2;/** * Edge flag indicating that the left edge should be affected. */public static final int EDGE_LEFT = 1 << 0;/** * Edge flag indicating that the right edge should be affected. */public static final int EDGE_RIGHT = 1 << 1;/** * Edge flag indicating that the top edge should be affected. */public static final int EDGE_TOP = 1 << 2;/** * Edge flag indicating that the bottom edge should be affected. */public static final int EDGE_BOTTOM = 1 << 3;/** * Edge flag set indicating all edges should be affected. */public static final int EDGE_ALL = EDGE_LEFT | EDGE_TOP | EDGE_RIGHT | EDGE_BOTTOM;/** * Indicates that a check should occur along the horizontal axis */public static final int DIRECTION_HORIZONTAL = 1 << 0;/** * Indicates that a check should occur along the vertical axis */public static final int DIRECTION_VERTICAL = 1 << 1;/** * Indicates that a check should occur along all axes */public static final int DIRECTION_ALL = DIRECTION_HORIZONTAL | DIRECTION_VERTICAL;public static final int EDGE_SIZE = 20; // dpprivate static final int BASE_SETTLE_DURATION = 256; // msprivate static final int MAX_SETTLE_DURATION = 600; // ms// Current drag state; idle, dragging or settlingprivate int mDragState;// Distance to travel before a drag may beginprivate int mTouchSlop;// Last known position/pointer trackingprivate int mActivePointerId = INVALID_POINTER;private float[] mInitialMotionX;private float[] mInitialMotionY;private float[] mLastMotionX;private float[] mLastMotionY;private int[] mInitialEdgeTouched;private int[] mEdgeDragsInProgress;private int[] mEdgeDragsLocked;private int mPointersDown;private VelocityTracker mVelocityTracker;private float mMaxVelocity;private float mMinVelocity;private int mEdgeSize;private int mTrackingEdges;private ScrollerCompat mScroller;private final Callback mCallback;private View mCapturedView;private boolean mReleaseInProgress;private final ViewGroup mParentView;/** * A Callback is used as a communication channel with the ViewDragHelper * back to the parent view using it. <code>on*</code>methods are invoked on * siginficant events and several accessor methods are expected to provide * the ViewDragHelper with more information about the state of the parent * view upon request. The callback also makes decisions governing the range * and draggability of child views. */public static abstract class Callback {/** * Called when the drag state changes. See the <code>STATE_*</code> * constants for more information. * * @param state The new drag state * @see #STATE_IDLE * @see #STATE_DRAGGING * @see #STATE_SETTLING */public void onViewDragStateChanged(int state) {}/** * Called when the captured view's position changes as the result of a * drag or settle. * * @param changedView View whose position changed * @param left        New X coordinate of the left edge of the view * @param top         New Y coordinate of the top edge of the view * @param dx          Change in X position from the last call * @param dy          Change in Y position from the last call */public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {}/** * Called when a child view is captured for dragging or settling. The ID * of the pointer currently dragging the captured view is supplied. If * activePointerId is identified as {@link #INVALID_POINTER} the capture * is programmatic instead of pointer-initiated. * * @param capturedChild   Child view that was captured * @param activePointerId Pointer id tracking the child capture */public void onViewCaptured(View capturedChild, int activePointerId) {}/** * Called when the child view is no longer being actively dragged. The * fling velocity is also supplied, if relevant. The velocity values may * be clamped to system minimums or maximums. * <p> * Calling code may decide to fling or otherwise release the view to let * it settle into place. It should do so using * {@link #settleCapturedViewAt(int, int)} or * {@link #flingCapturedView(int, int, int, int)}. If the Callback * invokes one of these methods, the ViewDragHelper will enter * {@link #STATE_SETTLING} and the view capture will not fully end until * it comes to a complete stop. If neither of these methods is invoked * before <code>onViewReleased</code> returns, the view will stop in * place and the ViewDragHelper will return to {@link #STATE_IDLE}. * </p> * * @param releasedChild The captured child view now being released * @param xvel          X velocity of the pointer as it left the screen in pixels *                      per second. * @param yvel          Y velocity of the pointer as it left the screen in pixels *                      per second. */public void onViewReleased(View releasedChild, float xvel, float yvel) {}/** * Called when one of the subscribed edges in the parent view has been * touched by the user while no child view is currently captured. * * @param edgeFlags A combination of edge flags describing the edge(s) *                  currently touched * @param pointerId ID of the pointer touching the described edge(s) * @see #EDGE_LEFT * @see #EDGE_TOP * @see #EDGE_RIGHT * @see #EDGE_BOTTOM */public void onEdgeTouched(int edgeFlags, int pointerId) {}/** * Called when the given edge may become locked. This can happen if an * edge drag was preliminarily rejected before beginning, but after * {@link #onEdgeTouched(int, int)} was called. This method should * return true to lock this edge or false to leave it unlocked. The * default behavior is to leave edges unlocked. * * @param edgeFlags A combination of edge flags describing the edge(s) *                  locked * @return true to lock the edge, false to leave it unlocked */public boolean onEdgeLock(int edgeFlags) {return false;}/** * Called when the user has started a deliberate drag away from one of * the subscribed edges in the parent view while no child view is * currently captured. * * @param edgeFlags A combination of edge flags describing the edge(s) *                  dragged * @param pointerId ID of the pointer touching the described edge(s) * @see #EDGE_LEFT * @see #EDGE_TOP * @see #EDGE_RIGHT * @see #EDGE_BOTTOM */public void onEdgeDragStarted(int edgeFlags, int pointerId) {}/** * Called to determine the Z-order of child views. * * @param index the ordered position to query for * @return index of the view that should be ordered at position * <code>index</code> */public int getOrderedChildIndex(int index) {return index;}/** * Return the magnitude of a draggable child view's horizontal range of * motion in pixels. This method should return 0 for views that cannot * move horizontally. * * @param child Child view to check * @return range of horizontal motion in pixels */public int getViewHorizontalDragRange(View child) {return 0;}/** * Return the magnitude of a draggable child view's vertical range of * motion in pixels. This method should return 0 for views that cannot * move vertically. * * @param child Child view to check * @return range of vertical motion in pixels */public int getViewVerticalDragRange(View child) {return 0;}/** * Called when the user's input indicates that they want to capture the * given child view with the pointer indicated by pointerId. The * callback should return true if the user is permitted to drag the * given view with the indicated pointer. * <p> * ViewDragHelper may call this method multiple times for the same view * even if the view is already captured; this indicates that a new * pointer is trying to take control of the view. * </p> * <p> * If this method returns true, a call to * {@link #onViewCaptured(View, int)} will follow if the * capture is successful. * </p> * * @param child     Child the user is attempting to capture * @param pointerId ID of the pointer attempting the capture * @return true if capture should be allowed, false otherwise */public abstract boolean tryCaptureView(View child, int pointerId);/** * Restrict the motion of the dragged child view along the horizontal * axis. The default implementation does not allow horizontal motion; * the extending class must override this method and provide the desired * clamping. * * @param child Child view being dragged * @param left  Attempted motion along the X axis * @param dx    Proposed change in position for left * @return The new clamped position for left */public int clampViewPositionHorizontal(View child, int left, int dx) {return 0;}/** * Restrict the motion of the dragged child view along the vertical * axis. The default implementation does not allow vertical motion; the * extending class must override this method and provide the desired * clamping. * * @param child Child view being dragged * @param top   Attempted motion along the Y axis * @param dy    Proposed change in position for top * @return The new clamped position for top */public int clampViewPositionVertical(View child, int top, int dy) {return 0;}}/** * Interpolator defining the animation curve for mScroller */private static final Interpolator sInterpolator = new Interpolator() {public float getInterpolation(float t) {t -= 1.0f;return t * t * t * t * t + 1.0f;}};private final Runnable mSetIdleRunnable = new Runnable() {public void run() {setDragState(STATE_IDLE);}};/** * Factory method to create a new ViewDragHelper. * * @param forParent Parent view to monitor * @param cb        Callback to provide information and receive events * @return a new ViewDragHelper instance */public static ViewDragHelper create(ViewGroup forParent, Callback cb) {return new ViewDragHelper(forParent.getContext(), forParent, cb);}/** * Factory method to create a new ViewDragHelper. * * @param forParent   Parent view to monitor * @param sensitivity Multiplier for how sensitive the helper should be *                    about detecting the start of a drag. Larger values are more *                    sensitive. 1.0f is normal. * @param cb          Callback to provide information and receive events * @return a new ViewDragHelper instance */public static ViewDragHelper create(ViewGroup forParent, float sensitivity, Callback cb) {final ViewDragHelper helper = create(forParent, cb);helper.mTouchSlop = (int) (helper.mTouchSlop * (1 / sensitivity));return helper;}/** * Apps should use ViewDragHelper.create() to get a new instance. This will * allow VDH to use internal compatibility implementations for different * platform versions. * * @param context   Context to initialize config-dependent params from * @param forParent Parent view to monitor */private ViewDragHelper(Context context, ViewGroup forParent, Callback cb) {if (forParent == null) {throw new IllegalArgumentException("Parent view may not be null");}if (cb == null) {throw new IllegalArgumentException("Callback may not be null");}mParentView = forParent;mCallback = cb;final ViewConfiguration vc = ViewConfiguration.get(context);final float density = context.getResources().getDisplayMetrics().density;mEdgeSize = (int) (EDGE_SIZE * density + 0.5f);mTouchSlop = vc.getScaledTouchSlop();mMaxVelocity = vc.getScaledMaximumFlingVelocity();mMinVelocity = vc.getScaledMinimumFlingVelocity();mScroller = ScrollerCompat.create(context, sInterpolator);}/** * Sets the sensitivity of the dragger. * * @param context     The application context. * @param sensitivity value between 0 and 1, the final value for touchSlop = *                    ViewConfiguration.getScaledTouchSlop * (1 / s); */public void setSensitivity(Context context, float sensitivity) {float s = Math.max(0f, Math.min(1.0f, sensitivity));ViewConfiguration viewConfiguration = ViewConfiguration.get(context);mTouchSlop = (int) (viewConfiguration.getScaledTouchSlop() * (1 / s));}/** * Set the minimum velocity that will be detected as having a magnitude * greater than zero in pixels per second. Callback methods accepting a * velocity will be clamped appropriately. * * @param minVel minimum velocity to detect */public void setMinVelocity(float minVel) {mMinVelocity = minVel;}/** * Set the max velocity that will be detected as having a magnitude * greater than zero in pixels per second. Callback methods accepting a * velocity will be clamped appropriately. * * @param maxVel max velocity to detect */public void setMaxVelocity(float maxVel) {mMaxVelocity = maxVel;}/** * Return the currently configured minimum velocity. Any flings with a * magnitude less than this value in pixels per second. Callback methods * accepting a velocity will receive zero as a velocity value if the real * detected velocity was below this threshold. * * @return the minimum velocity that will be detected */public float getMinVelocity() {return mMinVelocity;}/** * Retrieve the current drag state of this helper. This will return one of * {@link #STATE_IDLE}, {@link #STATE_DRAGGING} or {@link #STATE_SETTLING}. * * @return The current drag state */public int getViewDragState() {return mDragState;}/** * Enable edge tracking for the selected edges of the parent view. The * callback's * {@link me.imid.swipebacklayout.lib.ViewDragHelper.Callback#onEdgeTouched(int, int)} * and * {@link me.imid.swipebacklayout.lib.ViewDragHelper.Callback#onEdgeDragStarted(int, int)} * methods will only be invoked for edges for which edge tracking has been * enabled. * * @param edgeFlags Combination of edge flags describing the edges to watch * @see #EDGE_LEFT * @see #EDGE_TOP * @see #EDGE_RIGHT * @see #EDGE_BOTTOM */public void setEdgeTrackingEnabled(int edgeFlags) {mTrackingEdges = edgeFlags;}/** * Return the size of an edge. This is the range in pixels along the edges * of this view that will actively detect edge touches or drags if edge * tracking is enabled. * * @return The size of an edge in pixels * @see #setEdgeTrackingEnabled(int) */public int getEdgeSize() {return mEdgeSize;}/** * Set the size of an edge. This is the range in pixels along the edges of * this view that will actively detect edge touches or drags if edge * tracking is enabled. * * @param size The size of an edge in pixels */public void setEdgeSize(int size) {mEdgeSize = size;}/** * Capture a specific child view for dragging within the parent. The * callback will be notified but * {@link me.imid.swipebacklayout.lib.ViewDragHelper.Callback#tryCaptureView(View, int)} * will not be asked permission to capture this view. * * @param childView       Child view to capture * @param activePointerId ID of the pointer that is dragging the captured *                        child view */public void captureChildView(View childView, int activePointerId) {if (childView.getParent() != mParentView) {throw new IllegalArgumentException("captureChildView: parameter must be a descendant "                                   + "of the ViewDragHelper's tracked parent view (" + mParentView + ")");}mCapturedView = childView;mActivePointerId = activePointerId;mCallback.onViewCaptured(childView, activePointerId);setDragState(STATE_DRAGGING);}/** * @return The currently captured view, or null if no view has been * captured. */public View getCapturedView() {return mCapturedView;}/** * @return The ID of the pointer currently dragging the captured view, or * {@link #INVALID_POINTER}. */public int getActivePointerId() {return mActivePointerId;}/** * @return The minimum distance in pixels that the user must travel to * initiate a drag */public int getTouchSlop() {return mTouchSlop;}/** * The result of a call to this method is equivalent to * {@link #processTouchEvent(MotionEvent)} receiving an * ACTION_CANCEL event. */public void cancel() {mActivePointerId = INVALID_POINTER;clearMotionHistory();if (mVelocityTracker != null) {mVelocityTracker.recycle();mVelocityTracker = null;}}/** * {@link #cancel()}, but also abort all motion in progress and snap to the * end of any animation. */public void abort() {cancel();if (mDragState == STATE_SETTLING) {final int oldX = mScroller.getCurrX();final int oldY = mScroller.getCurrY();mScroller.abortAnimation();final int newX = mScroller.getCurrX();final int newY = mScroller.getCurrY();mCallback.onViewPositionChanged(mCapturedView, newX, newY, newX - oldX, newY - oldY);}setDragState(STATE_IDLE);}/** * Animate the view <code>child</code> to the given (left, top) position. If * this method returns true, the caller should invoke * {@link #continueSettling(boolean)} on each subsequent frame to continue * the motion until it returns false. If this method returns false there is * no further work to do to complete the movement. * <p> * This operation does not count as a capture event, though * {@link #getCapturedView()} will still report the sliding view while the * slide is in progress. * </p> * * @param child     Child view to capture and animate * @param finalLeft Final left position of child * @param finalTop  Final top position of child * @return true if animation should continue through * {@link #continueSettling(boolean)} calls */public boolean smoothSlideViewTo(View child, int finalLeft, int finalTop) {mCapturedView = child;mActivePointerId = INVALID_POINTER;return forceSettleCapturedViewAt(finalLeft, finalTop, 0, 0);}/** * Settle the captured view at the given (left, top) position. The * appropriate velocity from prior motion will be taken into account. If * this method returns true, the caller should invoke * {@link #continueSettling(boolean)} on each subsequent frame to continue * the motion until it returns false. If this method returns false there is * no further work to do to complete the movement. * * @param finalLeft Settled left edge position for the captured view * @param finalTop  Settled top edge position for the captured view * @return true if animation should continue through * {@link #continueSettling(boolean)} calls */public boolean settleCapturedViewAt(int finalLeft, int finalTop) {if (!mReleaseInProgress) {throw new IllegalStateException("Cannot settleCapturedViewAt outside of a call to "                                + "Callback#onViewReleased");}return forceSettleCapturedViewAt(finalLeft, finalTop,                                 (int) VelocityTrackerCompat.getXVelocity(mVelocityTracker, mActivePointerId),                                 (int) VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId));}/** * Settle the captured view at the given (left, top) position. * * @param finalLeft Target left position for the captured view * @param finalTop  Target top position for the captured view * @param xvel      Horizontal velocity * @param yvel      Vertical velocity * @return true if animation should continue through * {@link #continueSettling(boolean)} calls */private boolean forceSettleCapturedViewAt(int finalLeft, int finalTop, int xvel, int yvel) {final int startLeft = mCapturedView.getLeft();final int startTop = mCapturedView.getTop();final int dx = finalLeft - startLeft;final int dy = finalTop - startTop;if (dx == 0 && dy == 0) {// Nothing to do. Send callbacks, be done.mScroller.abortAnimation();setDragState(STATE_IDLE);return false;}final int duration = computeSettleDuration(mCapturedView, dx, dy, xvel, yvel);mScroller.startScroll(startLeft, startTop, dx, dy, duration);setDragState(STATE_SETTLING);return true;}private int computeSettleDuration(View child, int dx, int dy, int xvel, int yvel) {xvel = clampMag(xvel, (int) mMinVelocity, (int) mMaxVelocity);yvel = clampMag(yvel, (int) mMinVelocity, (int) mMaxVelocity);final int absDx = Math.abs(dx);final int absDy = Math.abs(dy);final int absXVel = Math.abs(xvel);final int absYVel = Math.abs(yvel);final int addedVel = absXVel + absYVel;final int addedDistance = absDx + absDy;final float xweight = xvel != 0 ? (float) absXVel / addedVel : (float) absDx                                                               / addedDistance;final float yweight = yvel != 0 ? (float) absYVel / addedVel : (float) absDy                                                               / addedDistance;int xduration = computeAxisDuration(dx, xvel, mCallback.getViewHorizontalDragRange(child));int yduration = computeAxisDuration(dy, yvel, mCallback.getViewVerticalDragRange(child));return (int) (xduration * xweight + yduration * yweight);}private int computeAxisDuration(int delta, int velocity, int motionRange) {if (delta == 0) {return 0;}final int width = mParentView.getWidth();final int halfWidth = width / 2;final float distanceRatio = Math.min(1f, (float) Math.abs(delta) / width);final float distance = halfWidth + halfWidth                                   * distanceInfluenceForSnapDuration(distanceRatio);int duration;velocity = Math.abs(velocity);if (velocity > 0) {duration = 4 * Math.round(1000 * Math.abs(distance / velocity));} else {final float range = (float) Math.abs(delta) / motionRange;duration = (int) ((range + 1) * BASE_SETTLE_DURATION);}return Math.min(duration, MAX_SETTLE_DURATION);}/** * Clamp the magnitude of value for absMin and absMax. If the value is below * the minimum, it will be clamped to zero. If the value is above the * maximum, it will be clamped to the maximum. * * @param value  Value to clamp * @param absMin Absolute value of the minimum significant value to return * @param absMax Absolute value of the maximum value to return * @return The clamped value with the same sign as <code>value</code> */private int clampMag(int value, int absMin, int absMax) {final int absValue = Math.abs(value);if (absValue < absMin) { return 0; }if (absValue > absMax) { return value > 0 ? absMax : -absMax; }return value;}/** * Clamp the magnitude of value for absMin and absMax. If the value is below * the minimum, it will be clamped to zero. If the value is above the * maximum, it will be clamped to the maximum. * * @param value  Value to clamp * @param absMin Absolute value of the minimum significant value to return * @param absMax Absolute value of the maximum value to return * @return The clamped value with the same sign as <code>value</code> */private float clampMag(float value, float absMin, float absMax) {final float absValue = Math.abs(value);if (absValue < absMin) { return 0; }if (absValue > absMax) { return value > 0 ? absMax : -absMax; }return value;}private float distanceInfluenceForSnapDuration(float f) {f -= 0.5f; // center the values about 0.f *= 0.3f * Math.PI / 2.0f;return (float) Math.sin(f);}/** * Settle the captured view based on standard free-moving fling behavior. * The caller should invoke {@link #continueSettling(boolean)} on each * subsequent frame to continue the motion until it returns false. * * @param minLeft Minimum X position for the view's left edge * @param minTop  Minimum Y position for the view's top edge * @param maxLeft Maximum X position for the view's left edge * @param maxTop  Maximum Y position for the view's top edge */public void flingCapturedView(int minLeft, int minTop, int maxLeft, int maxTop) {if (!mReleaseInProgress) {throw new IllegalStateException("Cannot flingCapturedView outside of a call to "                                + "Callback#onViewReleased");}mScroller.fling(mCapturedView.getLeft(), mCapturedView.getTop(),                (int) VelocityTrackerCompat.getXVelocity(mVelocityTracker, mActivePointerId),                (int) VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId),                minLeft, maxLeft, minTop, maxTop);setDragState(STATE_SETTLING);}/** * Move the captured settling view by the appropriate amount for the current * time. If <code>continueSettling</code> returns true, the caller should * call it again on the next frame to continue. * * @param deferCallbacks true if state callbacks should be deferred via *                       posted message. Set this to true if you are calling this *                       method from {@link View#computeScroll()} or *                       similar methods invoked as part of layout or drawing. * @return true if settle is still in progress */public boolean continueSettling(boolean deferCallbacks) {if (mDragState == STATE_SETTLING) {boolean keepGoing = mScroller.computeScrollOffset();final int x = mScroller.getCurrX();final int y = mScroller.getCurrY();final int dx = x - mCapturedView.getLeft();final int dy = y - mCapturedView.getTop();if (dx != 0) {mCapturedView.offsetLeftAndRight(dx);}if (dy != 0) {mCapturedView.offsetTopAndBottom(dy);}if (dx != 0 || dy != 0) {mCallback.onViewPositionChanged(mCapturedView, x, y, dx, dy);}if (keepGoing && x == mScroller.getFinalX() && y == mScroller.getFinalY()) {// Close enough. The interpolator/scroller might think we're// still moving// but the user sure doesn't.mScroller.abortAnimation();keepGoing = mScroller.isFinished();}if (!keepGoing) {if (deferCallbacks) {mParentView.post(mSetIdleRunnable);} else {setDragState(STATE_IDLE);}}}return mDragState == STATE_SETTLING;}/** * Like all callback events this must happen on the UI thread, but release * involves some extra semantics. During a release (mReleaseInProgress) is * the only time it is valid to call {@link #settleCapturedViewAt(int, int)} * or {@link #flingCapturedView(int, int, int, int)}. */private void dispatchViewReleased(float xvel, float yvel) {mReleaseInProgress = true;mCallback.onViewReleased(mCapturedView, xvel, yvel);mReleaseInProgress = false;if (mDragState == STATE_DRAGGING) {// onViewReleased didn't call a method that would have changed this.// Go idle.setDragState(STATE_IDLE);}}private void clearMotionHistory() {if (mInitialMotionX == null) {return;}Arrays.fill(mInitialMotionX, 0);Arrays.fill(mInitialMotionY, 0);Arrays.fill(mLastMotionX, 0);Arrays.fill(mLastMotionY, 0);Arrays.fill(mInitialEdgeTouched, 0);Arrays.fill(mEdgeDragsInProgress, 0);Arrays.fill(mEdgeDragsLocked, 0);mPointersDown = 0;}private void clearMotionHistory(int pointerId) {if (mInitialMotionX == null) {return;}mInitialMotionX[pointerId] = 0;mInitialMotionY[pointerId] = 0;mLastMotionX[pointerId] = 0;mLastMotionY[pointerId] = 0;mInitialEdgeTouched[pointerId] = 0;mEdgeDragsInProgress[pointerId] = 0;mEdgeDragsLocked[pointerId] = 0;mPointersDown &= ~(1 << pointerId);}private void ensureMotionHistorySizeForId(int pointerId) {if (mInitialMotionX == null || mInitialMotionX.length <= pointerId) {float[] imx = new float[pointerId + 1];float[] imy = new float[pointerId + 1];float[] lmx = new float[pointerId + 1];float[] lmy = new float[pointerId + 1];int[] iit = new int[pointerId + 1];int[] edip = new int[pointerId + 1];int[] edl = new int[pointerId + 1];if (mInitialMotionX != null) {System.arraycopy(mInitialMotionX, 0, imx, 0, mInitialMotionX.length);System.arraycopy(mInitialMotionY, 0, imy, 0, mInitialMotionY.length);System.arraycopy(mLastMotionX, 0, lmx, 0, mLastMotionX.length);System.arraycopy(mLastMotionY, 0, lmy, 0, mLastMotionY.length);System.arraycopy(mInitialEdgeTouched, 0, iit, 0, mInitialEdgeTouched.length);System.arraycopy(mEdgeDragsInProgress, 0, edip, 0, mEdgeDragsInProgress.length);System.arraycopy(mEdgeDragsLocked, 0, edl, 0, mEdgeDragsLocked.length);}mInitialMotionX = imx;mInitialMotionY = imy;mLastMotionX = lmx;mLastMotionY = lmy;mInitialEdgeTouched = iit;mEdgeDragsInProgress = edip;mEdgeDragsLocked = edl;}}private void saveInitialMotion(float x, float y, int pointerId) {ensureMotionHistorySizeForId(pointerId);mInitialMotionX[pointerId] = mLastMotionX[pointerId] = x;mInitialMotionY[pointerId] = mLastMotionY[pointerId] = y;mInitialEdgeTouched[pointerId] = getEdgeTouched((int) x, (int) y);mPointersDown |= 1 << pointerId;}private void saveLastMotion(MotionEvent ev) {final int pointerCount = MotionEventCompat.getPointerCount(ev);for (int i = 0; i < pointerCount; i++) {final int pointerId = MotionEventCompat.getPointerId(ev, i);final float x = MotionEventCompat.getX(ev, i);final float y = MotionEventCompat.getY(ev, i);mLastMotionX[pointerId] = x;mLastMotionY[pointerId] = y;}}/** * Check if the given pointer ID represents a pointer that is currently down * (to the best of the ViewDragHelper's knowledge). * <p> * The state used to report this information is populated by the methods * {@link #shouldInterceptTouchEvent(MotionEvent)} or * {@link #processTouchEvent(MotionEvent)}. If one of these * methods has not been called for all relevant MotionEvents to track, the * information reported by this method may be stale or incorrect. * </p> * * @param pointerId pointer ID to check; corresponds to IDs provided by *                  MotionEvent * @return true if the pointer with the given ID is still down */public boolean isPointerDown(int pointerId) {return (mPointersDown & 1 << pointerId) != 0;}void setDragState(int state) {if (mDragState != state) {mDragState = state;mCallback.onViewDragStateChanged(state);if (state == STATE_IDLE) {mCapturedView = null;}}}/** * Attempt to capture the view with the given pointer ID. The callback will * be involved. This will put us into the "dragging" state. If we've already * captured this view with this pointer this method will immediately return * true without consulting the callback. * * @param toCapture View to capture * @param pointerId Pointer to capture with * @return true if capture was successful */boolean tryCaptureViewForDrag(View toCapture, int pointerId) {if (toCapture == mCapturedView && mActivePointerId == pointerId) {// Already done!return true;}if (toCapture != null && mCallback.tryCaptureView(toCapture, pointerId)) {mActivePointerId = pointerId;captureChildView(toCapture, pointerId);return true;}return false;}/** * Tests scrollability within child views of v given a delta of dx. * * @param v      View to test for horizontal scrollability * @param checkV Whether the view v passed should itself be checked for *               scrollability (true), or just its children (false). * @param dx     Delta scrolled in pixels along the X axis * @param dy     Delta scrolled in pixels along the Y axis * @param x      X coordinate of the active touch point * @param y      Y coordinate of the active touch point * @return true if child views of v can be scrolled by delta of dx. */protected boolean canScroll(View v, boolean checkV, int dx, int dy, int x, int y) {if (v instanceof ViewGroup) {final ViewGroup group = (ViewGroup) v;final int scrollX = v.getScrollX();final int scrollY = v.getScrollY();final int count = group.getChildCount();// Count backwards - let topmost views consume scroll distance// first.for (int i = count - 1; i >= 0; i--) {// TODO: Add versioned support here for transformed views.// This will not work for transformed views in Honeycomb+final View child = group.getChildAt(i);if (x + scrollX >= child.getLeft()    && x + scrollX < child.getRight()    && y + scrollY >= child.getTop()    && y + scrollY < child.getBottom()    && canScroll(child, true, dx, dy, x + scrollX - child.getLeft(), y                                                                     + scrollY - child.getTop())) {return true;}}}return checkV       && (ViewCompat.canScrollHorizontally(v, -dx) || ViewCompat.canScrollVertically(v,                                                                                      -dy));}/** * Check if this event as provided to the parent view's * onInterceptTouchEvent should cause the parent to intercept the touch * event stream. * * @param ev MotionEvent provided to onInterceptTouchEvent * @return true if the parent view should return true from * onInterceptTouchEvent */public boolean shouldInterceptTouchEvent(MotionEvent ev) {final int action = MotionEventCompat.getActionMasked(ev);final int actionIndex = MotionEventCompat.getActionIndex(ev);if (action == MotionEvent.ACTION_DOWN) {// Reset things for a new event stream, just in case we didn't get// the whole previous stream.cancel();}if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(ev);switch (action) {case MotionEvent.ACTION_DOWN: {final float x = ev.getX();final float y = ev.getY();final int pointerId = MotionEventCompat.getPointerId(ev, 0);saveInitialMotion(x, y, pointerId);final View toCapture = findTopChildUnder((int) x, (int) y);// Catch a settling view if possible.if (toCapture == mCapturedView && mDragState == STATE_SETTLING) {tryCaptureViewForDrag(toCapture, pointerId);}final int edgesTouched = mInitialEdgeTouched[pointerId];if ((edgesTouched & mTrackingEdges) != 0) {mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);}break;}case MotionEventCompat.ACTION_POINTER_DOWN: {final int pointerId = MotionEventCompat.getPointerId(ev, actionIndex);final float x = MotionEventCompat.getX(ev, actionIndex);final float y = MotionEventCompat.getY(ev, actionIndex);saveInitialMotion(x, y, pointerId);// A ViewDragHelper can only manipulate one view at a time.if (mDragState == STATE_IDLE) {final int edgesTouched = mInitialEdgeTouched[pointerId];if ((edgesTouched & mTrackingEdges) != 0) {mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);}} else if (mDragState == STATE_SETTLING) {// Catch a settling view if possible.final View toCapture = findTopChildUnder((int) x, (int) y);if (toCapture == mCapturedView) {tryCaptureViewForDrag(toCapture, pointerId);}}break;}case MotionEvent.ACTION_MOVE: {// First to cross a touch slop over a draggable view wins. Also// report edge drags.final int pointerCount = MotionEventCompat.getPointerCount(ev);for (int i = 0; i < pointerCount; i++) {final int pointerId = MotionEventCompat.getPointerId(ev, i);final float x = MotionEventCompat.getX(ev, i);final float y = MotionEventCompat.getY(ev, i);final float dx = x - mInitialMotionX[pointerId];final float dy = y - mInitialMotionY[pointerId];reportNewEdgeDrags(dx, dy, pointerId);if (mDragState == STATE_DRAGGING) {// Callback might have started an edge dragbreak;}final View toCapture = findTopChildUnder((int) x, (int) y);if (toCapture != null && checkTouchSlop(toCapture, dx, dy)    && tryCaptureViewForDrag(toCapture, pointerId)) {break;}}saveLastMotion(ev);break;}case MotionEventCompat.ACTION_POINTER_UP: {final int pointerId = MotionEventCompat.getPointerId(ev, actionIndex);clearMotionHistory(pointerId);break;}case MotionEvent.ACTION_UP:case MotionEvent.ACTION_CANCEL: {cancel();break;}}return mDragState == STATE_DRAGGING;}/** * Process a touch event received by the parent view. This method will * dispatch callback events as needed before returning. The parent view's * onTouchEvent implementation should call this. * * @param ev The touch event received by the parent view */public void processTouchEvent(MotionEvent ev) {final int action = MotionEventCompat.getActionMasked(ev);final int actionIndex = MotionEventCompat.getActionIndex(ev);if (action == MotionEvent.ACTION_DOWN) {// Reset things for a new event stream, just in case we didn't get// the whole previous stream.cancel();}if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(ev);switch (action) {case MotionEvent.ACTION_DOWN: {final float x = ev.getX();final float y = ev.getY();final int pointerId = MotionEventCompat.getPointerId(ev, 0);final View toCapture = findTopChildUnder((int) x, (int) y);saveInitialMotion(x, y, pointerId);// Since the parent is already directly processing this touch// event,// there is no reason to delay for a slop before dragging.// Start immediately if possible.tryCaptureViewForDrag(toCapture, pointerId);final int edgesTouched = mInitialEdgeTouched[pointerId];if ((edgesTouched & mTrackingEdges) != 0) {mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);}break;}case MotionEventCompat.ACTION_POINTER_DOWN: {final int pointerId = MotionEventCompat.getPointerId(ev, actionIndex);final float x = MotionEventCompat.getX(ev, actionIndex);final float y = MotionEventCompat.getY(ev, actionIndex);saveInitialMotion(x, y, pointerId);// A ViewDragHelper can only manipulate one view at a time.if (mDragState == STATE_IDLE) {// If we're idle we can do anything! Treat it like a normal// down event.final View toCapture = findTopChildUnder((int) x, (int) y);tryCaptureViewForDrag(toCapture, pointerId);final int edgesTouched = mInitialEdgeTouched[pointerId];if ((edgesTouched & mTrackingEdges) != 0) {mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);}} else if (isCapturedViewUnder((int) x, (int) y)) {// We're still tracking a captured view. If the same view is// under this// point, we'll swap to controlling it with this pointer// instead.// (This will still work if we're "catching" a settling// view.)tryCaptureViewForDrag(mCapturedView, pointerId);}break;}case MotionEvent.ACTION_MOVE: {if (mDragState == STATE_DRAGGING) {final int index = MotionEventCompat.findPointerIndex(ev, mActivePointerId);final float x = MotionEventCompat.getX(ev, index);final float y = MotionEventCompat.getY(ev, index);final int idx = (int) (x - mLastMotionX[mActivePointerId]);final int idy = (int) (y - mLastMotionY[mActivePointerId]);dragTo(mCapturedView.getLeft() + idx, mCapturedView.getTop() + idy, idx, idy);saveLastMotion(ev);} else {// Check to see if any pointer is now over a draggable view.final int pointerCount = MotionEventCompat.getPointerCount(ev);for (int i = 0; i < pointerCount; i++) {final int pointerId = MotionEventCompat.getPointerId(ev, i);final float x = MotionEventCompat.getX(ev, i);final float y = MotionEventCompat.getY(ev, i);final float dx = x - mInitialMotionX[pointerId];final float dy = y - mInitialMotionY[pointerId];reportNewEdgeDrags(dx, dy, pointerId);if (mDragState == STATE_DRAGGING) {// Callback might have started an edge drag.break;}final View toCapture = findTopChildUnder((int) x, (int) y);if (checkTouchSlop(toCapture, dx, dy)    && tryCaptureViewForDrag(toCapture, pointerId)) {break;}}saveLastMotion(ev);}break;}case MotionEventCompat.ACTION_POINTER_UP: {final int pointerId = MotionEventCompat.getPointerId(ev, actionIndex);if (mDragState == STATE_DRAGGING && pointerId == mActivePointerId) {// Try to find another pointer that's still holding on to// the captured view.int newActivePointer = INVALID_POINTER;final int pointerCount = MotionEventCompat.getPointerCount(ev);for (int i = 0; i < pointerCount; i++) {final int id = MotionEventCompat.getPointerId(ev, i);if (id == mActivePointerId) {// This one's going away, skip.continue;}final float x = MotionEventCompat.getX(ev, i);final float y = MotionEventCompat.getY(ev, i);if (findTopChildUnder((int) x, (int) y) == mCapturedView    && tryCaptureViewForDrag(mCapturedView, id)) {newActivePointer = mActivePointerId;break;}}if (newActivePointer == INVALID_POINTER) {// We didn't find another pointer still touching the// view, release it.releaseViewForPointerUp();}}clearMotionHistory(pointerId);break;}case MotionEvent.ACTION_UP: {if (mDragState == STATE_DRAGGING) {releaseViewForPointerUp();}cancel();break;}case MotionEvent.ACTION_CANCEL: {if (mDragState == STATE_DRAGGING) {dispatchViewReleased(0, 0);}cancel();break;}}}private void reportNewEdgeDrags(float dx, float dy, int pointerId) {int dragsStarted = 0;if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_LEFT)) {dragsStarted |= EDGE_LEFT;}if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_TOP)) {dragsStarted |= EDGE_TOP;}if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_RIGHT)) {dragsStarted |= EDGE_RIGHT;}if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_BOTTOM)) {dragsStarted |= EDGE_BOTTOM;}if (dragsStarted != 0) {mEdgeDragsInProgress[pointerId] |= dragsStarted;mCallback.onEdgeDragStarted(dragsStarted, pointerId);}}private boolean checkNewEdgeDrag(float delta, float odelta, int pointerId, int edge) {final float absDelta = Math.abs(delta);final float absODelta = Math.abs(odelta);if ((mInitialEdgeTouched[pointerId] & edge) != edge || (mTrackingEdges & edge) == 0    || (mEdgeDragsLocked[pointerId] & edge) == edge    || (mEdgeDragsInProgress[pointerId] & edge) == edge    || (absDelta <= mTouchSlop && absODelta <= mTouchSlop)) {return false;}if (absDelta < absODelta * 0.5f && mCallback.onEdgeLock(edge)) {mEdgeDragsLocked[pointerId] |= edge;return false;}return (mEdgeDragsInProgress[pointerId] & edge) == 0 && absDelta > mTouchSlop;}/** * Check if we've crossed a reasonable touch slop for the given child view. * If the child cannot be dragged along the horizontal or vertical axis, * motion along that axis will not count toward the slop check. * * @param child Child to check * @param dx    Motion since initial position along X axis * @param dy    Motion since initial position along Y axis * @return true if the touch slop has been crossed */private boolean checkTouchSlop(View child, float dx, float dy) {if (child == null) {return false;}final boolean checkHorizontal = mCallback.getViewHorizontalDragRange(child) > 0;final boolean checkVertical = mCallback.getViewVerticalDragRange(child) > 0;if (checkHorizontal && checkVertical) {return dx * dx + dy * dy > mTouchSlop * mTouchSlop;} else if (checkHorizontal) {return Math.abs(dx) > mTouchSlop;} else if (checkVertical) {return Math.abs(dy) > mTouchSlop;}return false;}/** * Check if any pointer tracked in the current gesture has crossed the * required slop threshold. * <p> * This depends on internal state populated by * {@link #shouldInterceptTouchEvent(MotionEvent)} or * {@link #processTouchEvent(MotionEvent)}. You should only * rely on the results of this method after all currently available touch * data has been provided to one of these two methods. * </p> * * @param directions Combination of direction flags, see *                   {@link #DIRECTION_HORIZONTAL}, {@link #DIRECTION_VERTICAL}, *                   {@link #DIRECTION_ALL} * @return true if the slop threshold has been crossed, false otherwise */public boolean checkTouchSlop(int directions) {final int count = mInitialMotionX.length;for (int i = 0; i < count; i++) {if (checkTouchSlop(directions, i)) {return true;}}return false;}/** * Check if the specified pointer tracked in the current gesture has crossed * the required slop threshold. * <p> * This depends on internal state populated by * {@link #shouldInterceptTouchEvent(MotionEvent)} or * {@link #processTouchEvent(MotionEvent)}. You should only * rely on the results of this method after all currently available touch * data has been provided to one of these two methods. * </p> * * @param directions Combination of direction flags, see *                   {@link #DIRECTION_HORIZONTAL}, {@link #DIRECTION_VERTICAL}, *                   {@link #DIRECTION_ALL} * @param pointerId  ID of the pointer to slop check as specified by *                   MotionEvent * @return true if the slop threshold has been crossed, false otherwise */public boolean checkTouchSlop(int directions, int pointerId) {if (!isPointerDown(pointerId)) {return false;}final boolean checkHorizontal = (directions & DIRECTION_HORIZONTAL) == DIRECTION_HORIZONTAL;final boolean checkVertical = (directions & DIRECTION_VERTICAL) == DIRECTION_VERTICAL;final float dx = mLastMotionX[pointerId] - mInitialMotionX[pointerId];final float dy = mLastMotionY[pointerId] - mInitialMotionY[pointerId];if (checkHorizontal && checkVertical) {return dx * dx + dy * dy > mTouchSlop * mTouchSlop;} else if (checkHorizontal) {return Math.abs(dx) > mTouchSlop;} else if (checkVertical) {return Math.abs(dy) > mTouchSlop;}return false;}/** * Check if any of the edges specified were initially touched in the * currently active gesture. If there is no currently active gesture this * method will return false. * * @param edges Edges to check for an initial edge touch. See *              {@link #EDGE_LEFT}, {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, *              {@link #EDGE_BOTTOM} and {@link #EDGE_ALL} * @return true if any of the edges specified were initially touched in the * current gesture */public boolean isEdgeTouched(int edges) {final int count = mInitialEdgeTouched.length;for (int i = 0; i < count; i++) {if (isEdgeTouched(edges, i)) {return true;}}return false;}/** * Check if any of the edges specified were initially touched by the pointer * with the specified ID. If there is no currently active gesture or if * there is no pointer with the given ID currently down this method will * return false. * * @param edges Edges to check for an initial edge touch. See *              {@link #EDGE_LEFT}, {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, *              {@link #EDGE_BOTTOM} and {@link #EDGE_ALL} * @return true if any of the edges specified were initially touched in the * current gesture */public boolean isEdgeTouched(int edges, int pointerId) {return isPointerDown(pointerId) && (mInitialEdgeTouched[pointerId] & edges) != 0;}private void releaseViewForPointerUp() {mVelocityTracker.computeCurrentVelocity(1000, mMaxVelocity);final float xvel = clampMag(VelocityTrackerCompat.getXVelocity(mVelocityTracker, mActivePointerId),mMinVelocity, mMaxVelocity);final float yvel = clampMag(VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId),mMinVelocity, mMaxVelocity);dispatchViewReleased(xvel, yvel);}private void dragTo(int left, int top, int dx, int dy) {int clampedX = left;int clampedY = top;final int oldLeft = mCapturedView.getLeft();final int oldTop = mCapturedView.getTop();if (dx != 0) {clampedX = mCallback.clampViewPositionHorizontal(mCapturedView, left, dx);mCapturedView.offsetLeftAndRight(clampedX - oldLeft);}if (dy != 0) {clampedY = mCallback.clampViewPositionVertical(mCapturedView, top, dy);mCapturedView.offsetTopAndBottom(clampedY - oldTop);}if (dx != 0 || dy != 0) {final int clampedDx = clampedX - oldLeft;final int clampedDy = clampedY - oldTop;mCallback.onViewPositionChanged(mCapturedView, clampedX, clampedY, clampedDx, clampedDy);}}/** * Determine if the currently captured view is under the given point in the * parent view's coordinate system. If there is no captured view this method * will return false. * * @param x X position to test in the parent's coordinate system * @param y Y position to test in the parent's coordinate system * @return true if the captured view is under the given point, false * otherwise */public boolean isCapturedViewUnder(int x, int y) {return isViewUnder(mCapturedView, x, y);}/** * Determine if the supplied view is under the given point in the parent * view's coordinate system. * * @param view Child view of the parent to hit test * @param x    X position to test in the parent's coordinate system * @param y    Y position to test in the parent's coordinate system * @return true if the supplied view is under the given point, false * otherwise */public boolean isViewUnder(View view, int x, int y) {if (view == null) {return false;}return x >= view.getLeft() && x < view.getRight() && y >= view.getTop()       && y < view.getBottom();}/** * Find the topmost child under the given point within the parent view's * coordinate system. The child order is determined using * {@link me.imid.swipebacklayout.lib.ViewDragHelper.Callback#getOrderedChildIndex(int)} * . * * @param x X position to test in the parent's coordinate system * @param y Y position to test in the parent's coordinate system * @return The topmost child view under (x, y) or null if none found. */public View findTopChildUnder(int x, int y) {final int childCount = mParentView.getChildCount();for (int i = childCount - 1; i >= 0; i--) {final View child = mParentView.getChildAt(mCallback.getOrderedChildIndex(i));if (x >= child.getLeft() && x < child.getRight() && y >= child.getTop()    && y < child.getBottom()) {return child;}}return null;}private int getEdgeTouched(int x, int y) {int result = 0;if (x < mParentView.getLeft() + mEdgeSize) { result = EDGE_LEFT; }if (y < mParentView.getTop() + mEdgeSize) { result = EDGE_TOP; }if (x > mParentView.getRight() - mEdgeSize) { result = EDGE_RIGHT; }if (y > mParentView.getBottom() - mEdgeSize) { result = EDGE_BOTTOM; }return result;}}

四、SwipeBackActivityInterface:

package com.base.view.view.swipeback;/** * Author: walid ( copy to githup) * Date : 2016/03/21 18:00 */public interface SwipeBackActivityInterface {    /**     * @return the SwipeBackLayout associated with this activity.     */    SwipeBackLayout getSwipeBackLayout();    void setSwipeBackEnable(boolean enable);    /**     * Scroll out contentView and finish the activity     */    void scrollToFinishActivity();}


五、attr屬性:

<declare-styleable name="SwipeBackLayout"><attr name="edge_size" format="dimension"/><attr name="edge_flag"><enum name="left" value="0"/><enum name="right" value="1"/><enum name="bottom" value="2"/><enum name="all" value="3"/></attr><attr name="shadow_left" format="reference"/><attr name="shadow_right" format="reference"/><attr name="shadow_bottom" format="reference"/></declare-styleable><attr name="SwipeBackLayoutStyle" format="reference"/>

六、widget_swipeback_layout.xml:

<?xml version="1.0" encoding="utf-8"?><com.base.view.view.swipeback.SwipeBackLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:id="@+id/flSwipeBack"android:layout_width="match_parent"android:layout_height="match_parent"/>    

七、BaseActivity:

package com.xiaobai.mizar.android.ui.activity;/** * Author: walid (update) * Date : 2016/1/7 18:00 */public abstract class BaseXiaobaiActivity extends FragmentActivity implements SwipeBackActivityInterface {private SwipeBackActivityHelper backActivityHelper;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);if (savedInstanceState != null) {onCreateSavedInstanceState(savedInstanceState);}initSwipeBack();}private void initSwipeBack() {backActivityHelper = new SwipeBackActivityHelper(this);backActivityHelper.onActivityCreate();SwipeBackLayout swipeBackLayout = getSwipeBackLayout();swipeBackLayout.setEdgeTrackingEnabled(SwipeBackLayout.EDGE_LEFT);}@Overrideprotected void onPostCreate(Bundle savedInstanceState) {super.onPostCreate(savedInstanceState);backActivityHelper.onPostCreate();}@Overridepublic View findViewById(int id) {View v = super.findViewById(id);if (v == null && backActivityHelper != null) {return backActivityHelper.findViewById(id);}return v;}@Overridepublic SwipeBackLayout getSwipeBackLayout() {return backActivityHelper.getSwipeBackLayout();}@Overridepublic void setSwipeBackEnable(boolean enable) {getSwipeBackLayout().setEnableGesture(enable);}@Overridepublic void scrollToFinishActivity() {SwipeBackActivityHelper.convertActivityToTranslucent(this);getSwipeBackLayout().scrollToFinishActivity();}}


八、在Activity引入屬性:

      <item name="android:windowIsTranslucent">true</item>

至此:

     滑動刪除Activity操作就完成了;




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