Android中使用Content Providers进行数据共享的实例[页10]

javaCopy codepublic class MyContentProvider extends ContentProvider {

    private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    private static final int MY_DATA = 1;

    static {
        sUriMatcher.addURI("com.example.myapp.provider", "my_data", MY_DATA);
    }

    private SQLiteDatabase mDatabase;

    @Override
    public boolean onCreate() {
        mDatabase = new MyDatabaseHelper(getContext()).getWritableDatabase();
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        Cursor cursor;
        switch (sUriMatcher.match(uri)) {
            case MY_DATA:
                cursor = mDatabase.query("my_data", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        cursor.setNotificationUri(getContext().getContentResolver(), uri);
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        switch (sUriMatcher.match(uri)) {
            case MY_DATA:
                return "vnd.android.cursor.dir/my_data";
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        long id = mDatabase.insert("my_data", null, values);
        getContext().getContentResolver().notifyChange(uri, null);
        return ContentUris.withAppendedId(uri, id);
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        int count;
        switch (sUriMatcher.match(uri)) {
            case MY_DATA:
                count = mDatabase.delete("my_data", selection, selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return count;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        int count;
        switch (sUriMatcher.match(uri)) {
            case MY_DATA:
                count = mDatabase.update("my_data", values, selection, selectionArgs);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return count;
    }
}

上述代码中，首先定义了一个UriMatcher对象，用于匹配URI。在Content Provider的静态代码块中，将需要支持的URI添加到UriMatcher中。例如，"com.example.myapp.provider/my_data"这个URI对应的整数值为1。