android之网络资源多线程下载


package com.example.threaddown;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;

public class MainActivity extends Activity {

EditText url;
EditText target;
Button downBn;
ProgressBar bar;
DownUtil downUtil;
private int mDownStatus;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 获取程序界面中的三个界面控制
url = (EditText) findViewById(R.id.url);
target = (EditText) findViewById(R.id.target);
downBn = (Button) findViewById(R.id.downBn);
bar = (ProgressBar) findViewById(R.id.br);
// 创建一个Handler对象
final Handler handler = new Handler() {

@Override
public void handleMessage(Message msg) {
if (msg.what == 0x123) {
bar.setProgress(mDownStatus);
}
}

};
downBn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// 初始化DownUtil对象
downUtil = new DownUtil(url.getText().toString(), target
.getText().toString(), 6);
new Thread() {

@Override
public void run() {
try {
// 开始下载
downUtil.download();

} catch (Exception e) {
e.printStackTrace();
}
// 定义每秒调度获取一次系统的完成进度
final Timer timer = new Timer();
timer.schedule(new TimerTask() {

@Override
public void run() {
// 获取下载任务的完成比例
double completeRate = downUtil
.getCompleteRate();
mDownStatus = (int) (completeRate * 1000);
// 发送消息通知届满更新的进度条
handler.sendEmptyMessage(0x123);
// 下载完成之后取消任务进度
if (mDownStatus >= 100) {
timer.cancel();
}
}
}, 0, 1000);
}

}.start();
}
});
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}


package com.example.threaddown;

import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class DownUtil {

// 定义下载资源的路径
private String path;
// 指定所下载的文件的保存位置
private String targetFile;
// 定义需要使用多少线程下载资源
private int threadNum;
// 定义下载的线程对象
private DownThread[] threads;
// 定义下载的文件总大小
private int fileSize;

public DownUtil(String path, String targetFile, int threadNum) {
this.path = path;
this.targetFile = targetFile;
this.threadNum = threadNum;
}

public void download() throws IOException {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(5000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept", "*/*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Connection", "Keep-Alive");
// 得到文件的大小
fileSize = conn.getContentLength();
conn.disconnect();
int currentPartsSize = fileSize / threadNum + 1;
RandomAccessFile file = new RandomAccessFile(targetFile, "rw");
// 设置本地文件的大小
file.setLength(fileSize);
file.close();
for (int i = 0; i < threadNum; i++) {
// 计算每条线程的下载位置
int startPos = i * currentPartsSize;
// 每个线程使用一个RandomAccessFile进行下载
RandomAccessFile current = new RandomAccessFile(targetFile, "rw");
// 定义该线程的下载位置
current.seek(startPos);
// 创建下载线程
threads[i] = new DownThread(startPos, currentPartsSize, current);
// 启动线程下载
threads[i].start();
}

}

// 获取下载的完成百分比
public double getCompleteRate() {
// 统计多条线程已经下载的总大小
int sumSize = 0;
for (int i = 0; i < threadNum; i++) {
sumSize += threads[i].length;
}
return sumSize * 1.0 / fileSize;
}

private class DownThread extends Thread {
// 定义当前线程下载的位置
private int startPos;
// 定义当前线程下载文件的大小
private int currentPartsSize;
// 当前线程下载的文件块
private RandomAccessFile currentPart;
// 定义该线程已下载的字节数
private int length;

public DownThread(int startPos, int currentPartsSize,
RandomAccessFile currentPart) {
this.startPos = startPos;
this.currentPart = currentPart;
this.currentPartsSize = currentPartsSize;

}

@Override
public void run() {
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setConnectTimeout(5000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept", "*/*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Connection", "Keep-Alive");
InputStream in = conn.getInputStream();
in.skip(startPos);
int hasRead = 0;
byte[] buffer = new byte[1024];
// 读取网络数据,并写入本地文件
while (length < currentPartsSize
&& (hasRead = in.read(buffer)) > 0) {
currentPart.write(buffer, 0, hasRead);
// 累计该线程下载的总大小
length += hasRead;
}
currentPart.close();
in.close();

} catch (Exception e) {
e.printStackTrace();
}

}

}

}


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<EditText
android:id="@+id/url"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="http://ksoap2-android.googlecode.com/svn/m2-repo/com/google/code/ksoap2-android/ksoap2-android-assembly/3.1.0/ksoap2-android-assembly-3.1.0-jar-with-dependencies.jar" />

<EditText
android:id="@+id/target"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="/mnt/sdcard/"/>

<Button
android:id="@+id/downBn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="down" />

<ProgressBar
android:id="@+id/br"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

</LinearLayout>

    <!-- 在SD卡中创建与删除文件的权限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<!-- 在SD开中写入数据的权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<!-- 访问网路的权限 -->
<uses-permission android:name="android.permission.INTERNET" />



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