達內課程-SQLite（下）
最后一節，來做一個關於SQLite的項目
先做出以下界面
第一個頁面MainActivity對應的布局activity_main
<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" tools:context="com.example.xx.sqliteproject.MainActivity" android:orientation="vertical">
<Button android:id="@+id/btn_add" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="添加聯系人"/>
<ListView android:id="@+id/lv_contacts" android:layout_width="match_parent" android:layout_height="match_parent"/>
</LinearLayout>第二個ContactFormActivity對應的布局activity_contact_form
<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" tools:context="com.example.xx.sqliteproject.ContactFormActivity" android:orientation="vertical">
<TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="請輸入聯系人信息"/>
<EditText android:id="@+id/et_username" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="text" android:hint="請輸入聯系人姓名"/>
<EditText android:id="@+id/et_age" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="number" android:hint="請輸入聯系人年齡"/>
<EditText android:id="@+id/et_phone" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="number" android:hint="請輸入聯系人電話"/>
<EditText android:id="@+id/et_email" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="number" android:hint="請輸入聯系人Email"/>
<Button android:id="@+id/btn_save" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="保存"/>
</LinearLayout>
我們可以用一個DBOpenHelper來幫助我們管理數據庫，以免反復執行出錯
public class DBOpenHelper extends SQLiteOpenHelper{
//修改原來的構造方法
/* public DBOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) { super(context, name, factory, version); }*/
public DBOpenHelper(Context context) {
super(context, "test.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
//當創建數據庫時，直接創建數據表
String sql = "CREATE TABLE users ("+
"_id INTEGER PRIMARY KEY AUTOINCREMENT, "+
"_name VARCHAR(10) UNIQUE NOT NULL, "+
"_age INTEGER, "+
"_phone CHAR(11), "+
"_email VARCHAR(31) UNIQUE"+
")";
sqLiteDatabase.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
//當升級時
}
}
DBOpenHelper的onCreate()方法確保創建數據庫的時候執行，不創建的時候不反復執行
MainActivity
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private Button btn_add;
private ListView lv_contacts;
SQLiteOpenHelper s;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
DBOpenHelper dbOpenHelper = new DBOpenHelper(this);
//必須調用以下其中一個方法才能執行創建數據庫
//dbOpenHelper.getReadableDatabase();
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
}
private void initView() {
btn_add = findViewById(R.id.btn_add);
lv_contacts = findViewById(R.id.lv_contacts);
btn_add.setOnClickListener(this);
}
@Override
public void onClick(View view) {
Intent intent = new Intent(this,ContactFormActivity.class);
startActivity(intent);
}
}
項目結構如下圖
創建一個Person類
public class Person {
private String name;
private int age;
private String phone;
private String email;
public Person() {
}
public Person(String name, int age, String phone, String email) {
this.name = name;
this.age = age;
this.phone = phone;
this.email = email;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
創建接口IDao，實現相關功能
public interface IDao<T> {
long insert(T t);
}創建PersonDao
public class PersonDao implements IDao<Person> {
private Context context;
public PersonDao(Context context) {
setContext(context);
}
private void setContext(Context context) {
if(context == null){
throw new IllegalArgumentException("參數context不能為空");
}
this.context = context;
}
@Override
public long insert(Person person) {
//獲取SQLiteDatabase對象
DBOpenHelper dbOpenHelper = new DBOpenHelper(context);
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
//執行業務，增加數據
String table = "users";
String nullColumnHack = "_id";
ContentValues values = new ContentValues();
values.put("_name",person.getName());
values.put("_age",person.getAge());
values.put("_phone",person.getPhone());
values.put("_email",person.getEmail());
long id = db.insert(table,nullColumnHack,values);
//釋放資源
db.close();
db = null;
//返回
return id;
}
}ContractFormActivity
public class ContactFormActivity extends AppCompatActivity implements View.OnClickListener{
private EditText etUsername;
private EditText etAge;
private EditText etPhone;
private EditText etEmail;
private Button btnSave;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_contact_form);
initViews();
setListeners();
}
private void setListeners() {
btnSave.setOnClickListener(this);
}
private void initViews() {
etUsername = findViewById(R.id.et_username);
etAge = findViewById(R.id.et_age);
etPhone = findViewById(R.id.et_phone);
etEmail = findViewById(R.id.et_email);
btnSave = findViewById(R.id.btn_save);
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.btn_save:
//獲取表單中的數據
String name = etUsername.getText().toString().trim();
String phone = etPhone.getText().toString().trim();
String email = etEmail.getText().toString().trim();
int age = Integer.parseInt(etAge.getText().toString());
Person person = new Person(name,age,phone,email);
PersonDao personDao = new PersonDao(this);
long id = personDao.insert(person);
if(id == -1){
Toast.makeText(this,"姓名或電子郵件可能沖突！",Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(this,"數據增加成功",Toast.LENGTH_SHORT).show();
etUsername.setText(null);
etPhone.setText(null);
etEmail.setText(null);
etAge.setText(null);
}
break;
}
}
}
運行程序
可以在添加聯系人的列表增加返回按鈕
添加點擊監聽，點擊時，finish()當前頁面返回上一頁面
在上一頁中顯示聯系人列表
IDao中增加查詢方法
public interface IDao<T> {
long insert(T t);
List<T> query(String whereClause,String whereArgs,String orderBy);
}PersonDao中完善query方法
@Override
public List<Person> query(String whereClause, String[] whereArgs, String orderBy) {
//聲明返回值
List<Person> persons = new ArrayList<Person>();
//獲取SQLiteDatabase對象
DBOpenHelper dbOpenHelper = new DBOpenHelper(context);
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
//執行業務：查詢數據
String table = "users";
String[] columns = {"_id","_name","_age","_phone","_email"};
Cursor c = db.query(table, columns, whereClause, whereArgs, null, null, orderBy);
//將數據封裝到返回值中
for(c.moveToFirst();!c.moveToLast();c.moveToNext()){
Person p = new Person();
p.setId(c.getInt(0));
p.setName(c.getString(1));
p.setAge(c.getInt(2));
p.setPhone(c.getString(3));
p.setEmail(c.getString(4));
persons.add(p);
}
//釋放資源
db.close();
db = null;
//返回
return persons;
}因為查詢字段中有id字段，所以Person類中增加id字段
public class Person {
private int id;
private String name;
private int age;
private String phone;
private String email;
public Person() {
}
public Person(String name, int age, String phone, String email) {
this.name = name;
this.age = age;
this.phone = phone;
this.email = email;
}
public Person(int id, String name, int age, String phone, String email) {
this.id = id;
this.name = name;
this.age = age;
this.phone = phone;
this.email = email;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
......
}MainActivity中准備顯示列表的Adaper，把之前寫好的BaseAdapter拿過來用
BaseAdapter的源碼在達內課程-音樂播放器3.0(上)中
新建PersonAdapter
這里寫代碼片注意！
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