ContentProvider+ContentResolver实现应用程序内的数据共享

最新推荐文章于 2022-11-24 20:03:22 发布

原创最新推荐文章于 2022-11-24 20:03:22 发布 · 454 阅读

CC 4.0 BY-SA版权

本文详细介绍了一个使用Android SQLite数据库和ContentProvider实现数据存取的应用案例。通过具体代码展示了如何创建一个ContentProvider类来实现基本的数据操作，如增删改查，并在MainActivity中通过ContentResolver进行数据查询。

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新建一个应用程序

<1>新建一个内容提供者类>

public class MyProvider extends ContentProvider{

    private SQLiteDatabase sqLiteDatabase;

    @Override
    public boolean onCreate() {
        Log.i("test","onCreate");
        return false;

    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] strings, @Nullable String s, @Nullable String[] strings1, @Nullable String s1) {
        Log.i("test","query");
        DBHelper dbHelper=new DBHelper(getContext(),"jiaokaobaodian.db",null,3);
        sqLiteDatabase = dbHelper.getReadableDatabase();
        return sqLiteDatabase.rawQuery("select * from jiaokaobaodian",null);
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        Log.i("test","getType");
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues contentValues) {
        Log.i("test","insert");
        return null;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String s, @Nullable String[] strings) {
        Log.i("test","delete");
        return 0;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues contentValues, @Nullable String s, @Nullable String[] strings) {
        Log.i("test","update");
        return 0;
    }
}

<二>配置

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zking.y2_android16_sqlite">

    <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:authorities="com.zking.y2_android16_sqlite.MY"
        android:name="com.zking.provider.MyProvider"
        android:exported="true"
        android:enabled="true"
        ></provider>

    </application>

</manifest>

<三>再新建一个程序，得到内容的访问者

public class MainActivity extends AppCompatActivity {

    private ContentResolver contentResolver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //得到内容访问者
        contentResolver = getContentResolver();
    }
    public void query(View view){
        //查询`
        Uri uri=Uri.parse("content://com.zking.y2_android16_sqlite.MY");
        Cursor cursor=contentResolver.query(uri,null,null,null,null);
        while(cursor.moveToNext()){
            int uid=cursor.getInt(cursor.getColumnIndex("uid"));
            Log.i("test",""+uid);
        }
    }
}