ContentProvider、ContentResolver的主要代码

ContentProvider:

public class MyContentProvider extends ContentProvider {

    // 数据库名称
    private static final String DB_NAME = "my_db";
    // 数据库版本号
    private static final int DB_VERSION = 1;
    // 表名
    private static final String TABLE_NAME = "my_table";

    // ContentProvider的Uri
    public static final Uri CONTENT_URI = Uri.parse("content://com.example.mycontentprovider");

    // ContentProvider支持的MIME类型
    private static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.com.example.mycontentprovider";
    private static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.com.example.mycontentprovider";

    // 数据库操作对象
    private SQLiteDatabase db;

    @Override
    public boolean onCreate() {
        // 初始化数据库
        DBHelper dbHelper = new DBHelper(getContext(), DB_NAME, null, DB_VERSION);
        db = dbHelper.getWritableDatabase();
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        // 查询数据
        Cursor cursor = db.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
        // 设置通知Uri，当这个Uri发生变化时，ContentObserver会收到通知
        cursor.setNotificationUri(getContext().getContentResolver(), uri);
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        // 根据Uri返回对应的MIME类型
        switch (uriMatcher.match(uri)) {
            case URI_CODE_ALL:
                return CONTENT_TYPE;
            case URI_CODE_ONE:
                return CONTENT_ITEM_TYPE;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        // 插入数据
        long rowId = db.insert(TABLE_NAME, null, values);
        if (rowId > 0) {
            // 插入成功，返回新插入的数据的Uri
            Uri newUri = ContentUris.withAppendedId(uri, rowId);
            // 通知数据发生变化
            getContext().getContentResolver().notifyChange(newUri, null);
            return newUri;
        } else {
            // 插入失败
            throw new SQLException("Failed to insert row into " + uri);
        }
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        // 删除数据
        int count = db.delete(TABLE_NAME, selection, selectionArgs);
        if (count > 0) {
            // 删除成功，通知数据发生变化
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        // 更新数据
        int count = db.update(TABLE_NAME, values, selection, selectionArgs);
        if (count > 0) {
            // 更新成功，通知数据发生变化
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    // Uri匹配器
    private static final UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    private static final int URI_CODE_ALL = 1;
    private static final int URI_CODE_ONE = 2;

    static {
        uriMatcher.addURI("com.example.mycontentprovider", TABLE_NAME, URI_CODE_ALL);
        uriMatcher.addURI("com.example.mycontentprovider", TABLE_NAME + "/#", URI_CODE_ONE);
    }
}

ContentResolver:

public class MyActivity extends Activity {

    // ContentProvider的Uri
    private static final Uri CONTENT_URI = Uri.parse("content://com.example.mycontentprovider/my_table");
    // ContentProvider支持的MIME类型
    private static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.com.example.mycontentprovider";
    private static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.com.example.mycontentprovider";

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

        // 查询数据
        Cursor cursor = getContentResolver().query(CONTENT_URI, null, null, null, null);
        if (cursor != null) {
            while (cursor.moveToNext()) {
                String data = cursor.getString(cursor.getColumnIndex("data"));
                Log.d("MyActivity", "data: " + data);
            }
            cursor.close();
        }

        // 插入数据
        ContentValues values = new ContentValues();
        values.put("data", "Hello, ContentProvider!");
        Uri newUri = getContentResolver().insert(CONTENT_URI, values);
        Log.d("MyActivity", "newUri: " + newUri);

        // 更新数据
        values.put("data", "Hello, ContentResolver!");
        int count = getContentResolver().update(newUri, values, null, null);
        Log.d("MyActivity", "count: " + count);

        // 删除数据
        count = getContentResolver().delete(newUri, null, null);
        Log.d("MyActivity", "count: " + count);
    }
}