Android開發學習筆記整理（14）-ContentProvider和BroadcastReceive

代碼部分：

part1：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="insert"
            android:text="insert" />

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="delete"
            android:text="delete" />

        <Button
            android:id="@+id/button3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="update"
            android:text="update" />

        <Button
            android:id="@+id/button4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="query"
            android:text="query" />

    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {

    private ContentResolver contentResolver;

    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        contentResolver = getContentResolver();
    }

    /**
     * 演示ContentProvider的插入操作
     * @param view
     */
    public void insert(View view) {
        /*
         * content://bzxy.day13.demo/teacher
         * */
        // 定義Uri
        Uri uri = Uri.parse("content://bzxy.day13.demo/teacher");
        // 定義ContentValues
        ContentValues contentValues = new ContentValues();
        contentValues.put("name", "李老師");
        Uri result = contentResolver.insert(uri, contentValues);
        long id = ContentUris.parseId(result);
        Toast.makeText(this,"插入完成，插入數據的id是：" + id, Toast.LENGTH_SHORT).show();
    }

    /**
     * 演示ContentProvider的刪除操作
     * @param view
     */
    public void delete(View view) {
        Uri uri = Uri.parse("content://bzxy.day13.demo/teacher");
        int row = contentResolver.delete(uri, "id=?", new String[]{"1"});
        Toast.makeText(this, "刪除的數據條數是：" + row, Toast.LENGTH_SHORT).show();
    }

    /**
     * 演示ContentProvider的修改操作
     * @param view
     */
    public void update(View view) {
        Uri uri = Uri.parse("content://bzxy.day13.demo/student");
        ContentValues contentValues = new ContentValues();
        contentValues.put("name", "王五");
        int row = contentResolver.update(uri,contentValues,"id=?", new String[]{"3"});
        Toast.makeText(this, "更新的數據條數是：" + row, Toast.LENGTH_SHORT).show();
    }

    /**
     * 演示ContentProvider的查詢操作
     * @param view
     */
    public void query(View view) {
        Uri uri = Uri.parse("content://bzxy.day13.demo/student");
        Cursor cursor = contentResolver.query(uri,null,null,null,null);
        while(cursor.moveToNext()) {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String name = cursor.getString(cursor.getColumnIndex("name"));
            Log.i(TAG, "學生的id是："+id+",姓名是：" + name);
        }
    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.day13">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <provider
            android:name=".MyContentProvider"
            android:authorities="bzxy.day13.demo"
            android:exported="true" />
    </application>

</manifest>

DBHelper.java

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import androidx.annotation.Nullable;
public class DBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "demo";

    private static final int VERSION = 2;

    public DBHelper(@Nullable Context context) {
        super(context, DB_NAME, null, VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "create table if not exists student(id integer primary key autoincrement, name varchar not null)";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (oldVersion == 1 && newVersion == 2) {
            String sql = "create table if not exists teacher(id integer primary key autoincrement, name varchar not null)";
            db.execSQL(sql);
        }
    }
    
}

MyContentProvider.java

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
/**
 * 自定義ContentProvider
 */
public class MyContentProvider extends ContentProvider {

    private DBHelper dbHelper;

    private static UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

    // 配置UriMatcher
    static {
        uriMatcher.addURI("bzxy.day13.demo", "student", 1);
        uriMatcher.addURI("bzxy.day13.demo", "teacher", 2);
    }

    @Override
    public boolean onCreate() {
        dbHelper = new DBHelper(getContext());
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        SQLiteDatabase database = dbHelper.getReadableDatabase();
        Cursor cursor = null;
        switch (uriMatcher.match(uri)) {
            case 1:
                cursor = database.query("student", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            case 2:
                cursor = database.query("teacher", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            default:
                break;
        }
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        long id = 0;
        switch (uriMatcher.match(uri)) {
            case 1:
                id = database.insert("student",null, values);
                break;
            case 2:
                id = database.insert("teacher",null, values);
                break;
            default:
                break;
        }
        Uri newUri = ContentUris.withAppendedId(uri, id);
        database.close();
        return newUri;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        int row = 0;
        switch (uriMatcher.match(uri)){
            case 1:
                row = database.delete("student", selection, selectionArgs);
                break;
            case 2:
                row = database.delete("teacher", selection, selectionArgs);
                break;
            default:
                break;
        }
        database.close();
        return row;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        int row = 0;
        switch (uriMatcher.match(uri)) {
            case 1:
                row = database.update("student", values, selection, selectionArgs);
                break;
            case 2:
                row = database.update("teacher", values, selection, selectionArgs);
                break;
            default:
                break;
        }
        database.close();
        return row;
    }

}

part2：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="insert"
            android:text="insert" />

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="delete"
            android:text="delete" />

        <Button
            android:id="@+id/button3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="update"
            android:text="update" />

        <Button
            android:id="@+id/button4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="query"
            android:text="query" />
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class MainActivity extends AppCompatActivity {

    private ContentResolver contentResolver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        contentResolver = getContentResolver();
    }

    /**
     * 演示插入操作
     * @param view
     */
    public void insert(View view) {

    }

    /**
     * 演示刪除操作
     * @param view
     */
    public void delete(View view) {

    }

    /**
     * 演示更新操作
     * @param view
     */
    public void update(View view) {

    }

    /**
     * 演示查詢操作
     * @param view
     */
    public void query(View view) {
        Uri uri = Uri.parse("content://bzxy.day13.demo/teacher");
        Cursor cursor = contentResolver.query(uri,null,null,null,null);
        while(cursor.moveToNext()) {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String name = cursor.getString(cursor.getColumnIndex("name"));
            Log.i("demo", "老師的id是："+id+",姓名是：" + name);
        }
    }

}

part3：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="sendBroadcast"
        android:text="發送廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showLocalBroadcast"
        android:text="演示本地廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <Button
        android:id="@+id/button3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showRefresh"
        android:text="通過廣播進行列表刷新"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button2" />

</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

MyBroadcastReceiver.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
public class MyBroadcastReceiver extends BroadcastReceiver {

    /**
     * 接收到廣播的時候觸發
     * @param context
     * @param intent
     */
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"接收到廣播了", Toast.LENGTH_SHORT).show();
    }
    
}

MyReceiver.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
public class MyReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "廣播接收到了", Toast.LENGTH_SHORT).show();
    }
    
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.day13_broadcast">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".RefreshActivity"></activity>

        <receiver
            android:name=".MyReceiver"
            android:enabled="true"
            android:exported="true" />

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity> <!-- 廣播註冊 -->
        <receiver android:name=".MyBroadcastReceiver">
            <intent-filter>
                <action android:name="bzxy.day13.demo" />
            </intent-filter>
        </receiver>
    </application>

</manifest>

效果圖：

點擊發送廣播

part4：

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {

    /*
     * 什麼是廣播：對於Activity來講，觸發只能是一對一，做不到一對多。廣播可以彌補Activity的缺陷，做到消息的
     * 一對多傳遞。
     * 應用場景：非常廣闊，應用於監聽數據變化等等。
     * 實現廣播：
     *   1.廣播
     *   2.觸發:凡是可以觸發事件的地方，都可以觸發廣播
     *   3.訂閱廣播
     * 廣播訂閱：
     *   1.動態訂閱
     *   2.靜態訂閱
     * 廣播的分類
     *   1.系統廣播
     *   2.自定義廣播
     *       2.1順序廣播
     *       2.2正常廣播
     *   3.本地廣播（如果只是在本app中進行廣播的話，建議使用本地廣播）
     * */

    private MyBroadcastReceiver myBroadcastReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 訂閱廣播
//        myBroadcastReceiver = new MyBroadcastReceiver();
//        IntentFilter filter = new IntentFilter();
//        filter.addAction("bzxy.day13.demo");
//        registerReceiver(myBroadcastReceiver, filter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 取消訂閱
//        unregisterReceiver(myBroadcastReceiver);
    }

    /**
     * 發送廣播
     * @param view
     */
    public void sendBroadcast(View view) {
        Intent intent = new Intent();
//        intent.setAction("bzxy.day13.demo"); // 廣播的標識   day13_broadcast
        ComponentName componentName = new ComponentName("com.example.day13_broadcast",
                "com.example.day13_broadcast.MyReceiver");
        intent.setComponent(componentName);
        sendBroadcast(intent);
    }

    /**
     * 演示本地廣播
     * @param view
     */
    public void showLocalBroadcast(View view) {

    }

    public void showRefresh(View view) {
        Intent intent = new Intent(this, RefreshActivity.class);
        startActivity(intent);
    }

}

activity_refresh.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".RefreshActivity">

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

DBHelper.java

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import androidx.annotation.Nullable;
public class DBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "demo";
    private static final int VERSION = 1;

    public DBHelper(@Nullable Context context) {
        super(context, DB_NAME, null, VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "create table if not exists user (id integer primary key autoincrement, name varchar not null)";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
    
}

User.java

public class User {

    private int id;

    private String name;

    public User(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    
}

user_item.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/tv_id"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="47dp"
        android:layout_marginLeft="47dp"
        android:layout_marginTop="35dp"
        android:text="TextView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="35dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="23dp"
        android:layout_marginEnd="23dp"
        android:layout_marginRight="23dp"
        android:text="刪除"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

RefreshAdapter

import android.content.Context;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.TextView;
import java.util.List;
public class RefreshAdapter extends BaseAdapter {

    private List<User> data;

    private Context context;

    private LayoutInflater inflater;

    public RefreshAdapter(List<User> data, Context context) {
        this.data = data;
        this.context = context;
        inflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return data.size();
    }

    @Override
    public Object getItem(int position) {
        return data.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder viewHolder ;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.user_item, null);
            viewHolder = new ViewHolder();
            viewHolder.tv_id = convertView.findViewById(R.id.tv_id);
            viewHolder.tv_name = convertView.findViewById(R.id.tv_name);
            viewHolder.btn_delete = convertView.findViewById(R.id.btn_delete);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        final User user = data.get(position);
        viewHolder.tv_id.setText(user.getId()+"");
        viewHolder.tv_name.setText(user.getName());
        viewHolder.btn_delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 刪除數據
                DBHelper dbHelper = new DBHelper(context);
                SQLiteDatabase database = dbHelper.getWritableDatabase();
                int row = database.delete("user", "id=?", new String[]{user.getId()+""});
                // 發送廣播
                Intent intent = new Intent();
                intent.setAction("user.delete");
                context.sendBroadcast(intent);
            }
        });

        return convertView;
    }

    class ViewHolder {
        public TextView tv_id;
        public TextView tv_name;
        public Button btn_delete;
    }
    
}

RefreshActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.BroadcastReceiver;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.List;
public class RefreshActivity extends AppCompatActivity {

    private DBHelper dbHelper;

    private List<User> data;

    private RefreshAdapter adapter;

    private UserDeleteBroadcast userDeleteBroadcast;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_refresh);

        dbHelper = new DBHelper(this);
        SQLiteDatabase database = dbHelper.getWritableDatabase();

        // 準備數據
        for(int i=0; i<10; i++) {
            ContentValues contentValues = new ContentValues();
            contentValues.put("name", "張三"+i);
            database.insert("user", null, contentValues);
        }

        getData();

        // 初始化ListView
        ListView listView = findViewById(R.id.listView);
        adapter = new RefreshAdapter(data, this);
        listView.setAdapter(adapter);

        // 註冊廣播
        userDeleteBroadcast = new UserDeleteBroadcast();
        registerReceiver(userDeleteBroadcast,new IntentFilter("user.delete"));
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(userDeleteBroadcast);
    }

    /**
     * 創建廣播接收
     */
    private class UserDeleteBroadcast extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            // 查詢數據庫
            getData();
            // 更新列表
            adapter.notifyDataSetChanged();
        }
    }

    /**
     * 獲取數據
     */
    private void getData() {
        // 數據封裝
        SQLiteDatabase database = dbHelper.getWritableDatabase();
        Cursor cursor = database.query("user",null,null,null,null,null,null);
        if (data != null) {
            data.clear();
        } else {
            data = new ArrayList<>();
        }
        while(cursor.moveToNext()) {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String name = cursor.getString(cursor.getColumnIndex("name"));
            User user = new User(id,name);
            data.add(user);
        }
    }

}

效果圖：

點擊通過廣播進行列表刷新