java - 如何在RecyclerView中使用光标适配器制作多张卡片？

Question

我在 RecyclerView 中使用网格布局，其中每张卡都使用游标适配器和游标加载器显示来自 SQLite 数据库的一些信息。我用过library为了实现这一目标。

问题是所有卡片都没有显示。当我第一次运行该应用程序时，仅显示一张卡，其中显示数据库最后一行的数据。但我希望它显示第一行的数据。如果我关闭并再次运行应用程序，则会显示两张卡，但两张卡都具有相同的数据，即再次来自数据库的最后一行。我希望第二张卡显示第二行的数据。第三次，显示三张牌并继续该模式。

请帮我显示每次从数据库中相应行获取数据时所需的确切卡片数量。

MainActivity.java

public class MainActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<Cursor>  {

    private RecyclerView recyclerView;
    private RecyclerViewAdapter adapter;

    ContentResolver contentResolver;

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

        contentResolver = getContentResolver();

        insertRecipes();

        recyclerView = (RecyclerView) findViewById(R.id.recycler_view);

        adapter = new RecyclerViewAdapter(getBaseContext());

        Log.v("MainActivity", "instantiating adapter");

        recyclerView.setAdapter(adapter);

        Log.v("MainActivity", "setting adapter");

        recyclerView.setLayoutManager(new GridLayoutManager(getBaseContext(), 2));

        Log.v("MainActivity", "setting layout manager for recycler view");

        getSupportLoaderManager().initLoader(0, null, this);
    }

    @Override
    protected void onStart() {
        super.onStart();
    }


    private void insertRecipes()
    {
        ContentValues values = new ContentValues();
        values.put(AppytizerEntry.COLUMN_APPYTIZER_NAME, "test name 1");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_INGREDIENTS, "chips, salt, pepper");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_DIRECTIONS, "mix chips, salt and pepper. eat it");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TOFDISH, AppytizerEntry.TOFDISH_VEGETARIAN);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_COURSE, AppytizerEntry.COURSE_SNACKS);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TIME, 2);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_CALORIES, 100);
        //values.put(AppytizerEntry.COLUMN_APPYTIZER_IMAGE, );

        values.put(AppytizerEntry.COLUMN_APPYTIZER_NAME, "test name 2");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_INGREDIENTS, "chips, salt, pepper");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_DIRECTIONS, "mix chips, salt and pepper. eat it");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TOFDISH, AppytizerEntry.TOFDISH_VEGETARIAN);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_COURSE, AppytizerEntry.COURSE_SNACKS);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TIME, 2);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_CALORIES, 100);
        //values.put(AppytizerEntry.COLUMN_APPYTIZER_IMAGE, );

        values.put(AppytizerEntry.COLUMN_APPYTIZER_NAME, "test name 3");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_INGREDIENTS, "chips, salt, pepper");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_DIRECTIONS, "mix chips, salt and pepper. eat it");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TOFDISH, AppytizerEntry.TOFDISH_VEGETARIAN);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_COURSE, AppytizerEntry.COURSE_SNACKS);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TIME, 2);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_CALORIES, 100);
        //values.put(AppytizerEntry.COLUMN_APPYTIZER_IMAGE, );

        values.put(AppytizerEntry.COLUMN_APPYTIZER_NAME, "test name 4");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_INGREDIENTS, "chips, salt, pepper");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_DIRECTIONS, "mix chips, salt and pepper. eat it");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TOFDISH, AppytizerEntry.TOFDISH_VEGETARIAN);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_COURSE, AppytizerEntry.COURSE_SNACKS);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TIME, 2);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_CALORIES, 100);
        //values.put(AppytizerEntry.COLUMN_APPYTIZER_IMAGE, );

        values.put(AppytizerEntry.COLUMN_APPYTIZER_NAME, "test name 5");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_INGREDIENTS, "chips, salt, pepper");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_DIRECTIONS, "mix chips, salt and pepper. eat it");
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TOFDISH, AppytizerEntry.TOFDISH_VEGETARIAN);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_COURSE, AppytizerEntry.COURSE_SNACKS);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_TIME, 2);
        values.put(AppytizerEntry.COLUMN_APPYTIZER_CALORIES, 100);
        //values.put(AppytizerEntry.COLUMN_APPYTIZER_IMAGE, );

        Uri returnedUri = contentResolver.insert(AppytizerEntry.CONTENT_URI, values);

    }

    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {

        String[] projection = {
                AppytizerEntry._ID,
                AppytizerEntry.COLUMN_APPYTIZER_NAME
        };

        Uri CONTENT_URI = AppytizerEntry.CONTENT_URI;
        CursorLoader cursorLoader = new CursorLoader(this, CONTENT_URI, projection, null, null, null);

        return cursorLoader;

    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        adapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        adapter.swapCursor(null);
    }
}

RecyclerViewAdapter.java

public class RecyclerViewAdapter extends RecyclerViewCursorAdapter<RecyclerViewAdapter.MyViewHolder> {

public RecyclerViewAdapter(Context context)
{
    super(context);

    setupCursorAdapter(null, 0, R.layout.custom_row, false);

    Log.v("Adapter", "RecyclerViewAdapter constructor");
}


@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    Log.v("Adapter", "onCreateViewHolder");
    return new MyViewHolder(mCursorAdapter.newView(mContext, mCursorAdapter.getCursor(), parent));
}

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {

    Log.v("Adapter", "onBindViewHolder");

    mCursorAdapter.getCursor().moveToFirst();

    Log.v("Adapter", "moving to position " + position);

    setViewHolder(holder);
    mCursorAdapter.bindView(null, mContext, mCursorAdapter.getCursor());        
}

public class MyViewHolder extends RecyclerViewCursorViewHolder {

    public final TextView title;

    public MyViewHolder(View view)
    {
        super(view);

        Log.v("Adapter", "MyViewHolder constructor");

        title = (TextView) view.findViewById(R.id.title);
    }

    int i = 0;

    @Override
    public void bindCursor(Cursor cursor) {
        int titleColumnIndex = cursor.getColumnIndex(AppytizerContract.AppytizerEntry.COLUMN_APPYTIZER_NAME);

        title.setText(cursor.getString(titleColumnIndex));

        if(i<4)
        {
            cursor.moveToNext();
            i++;
        }

        Log.v("Adapter", "bindCursor");
    }
}

}

Answer 1

我对 ContentValues 不太熟悉，但是每个测试记录之间不应该有一个 database.insert(TABLE_NAME, null, contentValues); 吗？

Code example for ContentValues

这可以解释为什么您第一次只能看到最后一条记录，而第二次运行应用程序时会看到重复的记录。