Android——ContentProvider记录

ContentProvider可以在进程之间进行数据共享；记录一下关于数据库共享的信息

简单使用是比较简单的；

1，在app A 中；创建自己的ContentProvider

/**
 * Created by changquan on 2018/9/12.
 * 自定义内容提供者实现数据库共享
 */
public class MyProvider extends ContentProvider
{
    private static final int SUCCESS = 1;

    /** 判断Uri规则 */
    static UriMatcher mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    static {
        mUriMatcher.addURI("com.roi.sell_electricity", "account", SUCCESS);    //uri规则可自己定义，但一定和清单文件一直
    }

    @Override
    public boolean onCreate() {
        return false;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        int code = mUriMatcher.match(uri);
        if (SUCCESS == code)
        {
            Co_GreenDaoBeanDao dao = GreenDaoHelper.getDaoSession().getCo_GreenDaoBeanDao();
            return dao.getDatabase().rawQuery("select * from "+dao.getTablename(),null);
        }else
        {
            throw new IllegalArgumentException("路径不正确");
        }
    }

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

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        return null;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        return 0;
    }

}

2，注册

<!-- 注册内容提供者数据 -->
<provider
        android:exported="true"
        android:name=".MyProvider"
        android:authorities="com.roi.sell_electricity" >
</provider>

3，在另一个app B 上面获取共享数据库里面的数据

ContentResolver resolver = getContentResolver();
Uri uri = Uri.parse("content://com.roi.sell_electricity/account");
Cursor cursor = resolver.query(uri, null,
        null, null, null);
while (cursor.moveToNext())
{
    String username = cursor.getString(cursor.getColumnIndex("username"));
    String age = cursor.getString(cursor.getColumnIndex("AGE"));

    LogUtil.e("TestActivity","username:" + username + "age:" + age);
}
cursor.close();