回收器视图和卡片视图不显示卡片

Question

这是我的活动：

public String id;
public String passPhrase;
public ArrayList<SongCell> songs;

private RecyclerView recyclerView;
private MyAdapter myAdapter;
private RecyclerView.LayoutManager layoutManager;


@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.songs_view_layout);

    Context context = this.getApplicationContext();
    Bundle stateData = getIntent().getExtras();

    try
    {
        id = stateData.getString("id");
        passPhrase = stateData.getString("passPhrase");

        ArrayList data;

        recyclerView = (RecyclerView) findViewById(R.id.song_list);
        recyclerView.setHasFixedSize(true);

        layoutManager = new LinearLayoutManager(this);

        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());

        data = new ArrayList<SongCell>();

        for (int i=0; i<5;i++)
        {
            data.add(new SongCell("Song "+i,"Artist "+i, null));
        }


        myAdapter = new MyAdapter(data);
        recyclerView.setAdapter(myAdapter);

    }
    catch(Exception e)
    {
        Log.d("Error: ", e.toString());
    }

}

卡片xml

<android.support.v7.widget.CardView android:layout_width="fill_parent"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android">

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:padding="6dp"
        >

        <ImageView
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:id="@+id/song_photo"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true"
            android:layout_marginRight="16dp"
            android:background="@drawable/error" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/song_name"
            android:textSize="30sp"
            android:text="Song Name"
            android:layout_centerVertical="true"
            android:layout_centerHorizontal="true"
            android:textColor="#000000" />

        <ImageButton
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:id="@+id/vote_button"
            android:layout_alignParentRight="true"
            android:layout_marginRight="8dp"
            android:background="@drawable/arrow" />

    </RelativeLayout>

</android.support.v7.widget.CardView>

活动xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent"
android:background="#2d2d2d">

<TableLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TableRow
        android:layout_width="fill_parent"
        android:layout_height="match_parent"
        android:paddingBottom="30dp"
        android:layout_marginBottom="10dp"
        android:background="#222222"></TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:paddingBottom="10dp">

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center">

            <ImageView
                android:layout_width="70dp"
                android:layout_height="70dp"
                android:id="@+id/featSongImage1"
                android:contentDescription="@string/newsongimage"
                android:background="@drawable/error" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceSmall"
                android:text="@string/songname"
                android:id="@+id/featSongName1" />

            <ImageButton
                android:layout_width="25dp"
                android:layout_height="25dp"
                android:id="@+id/featSongButt1"
                android:background="@drawable/arrow"
                android:contentDescription="@string/votearrow" />
        </LinearLayout>

    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:foregroundGravity="fill_horizontal"
        android:gravity="fill_horizontal|center">




        <android.support.v7.widget.RecyclerView
            android:id="@+id/song_list"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_gravity="center_horizontal" />


    </TableRow>
</TableLayout>
</LinearLayout>

这是我的自定义适配器

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>
{
private ArrayList<SongCell> data;

public MyAdapter(ArrayList<SongCell> dataI)
{
    data = dataI;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType)
{
    View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.song_card,viewGroup,false);
    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(ViewHolder viewholder, int pos) {
    viewholder.songName.setText(data.get(pos).getName());
    viewholder.artist.setText(data.get(pos).getArtist());
    viewholder.image.setImageBitmap(data.get(pos).getArtwork());
}

@Override
public int getItemCount() {
    return 0;
}

@Override
public int getItemViewType(int position) {
    return 0;
}

public class ViewHolder extends RecyclerView.ViewHolder
{
    TextView songName;
    TextView artist;
    ImageView image;
    ImageButton voteButton;

    public ViewHolder(View v)
    {
        super(v);
        this.songName = (TextView) v.findViewById(R.id.song_name);
        this.image = (ImageView) v.findViewById(R.id.song_photo);
        this.voteButton = (ImageButton) v.findViewById(R.id.vote_button);
    }
}

}

我已经看了很多关于如何让它工作的指南，但它仍然不起作用。有人知道发生了什么事吗？我的版本是25.0。1，并导入所有模块。但它并没有在布局中添加一张卡片。

Answer 1

我想调试你上传的这么大的代码会很困难。但幸运的是，我的眼睛盯着这条线

@Override
public int getItemCount() {
    return 0;
}

返回0 在适配器中。

您的列表大小始终为0。

而是写下这个

@Override
public int getItemCount() {
    return data.size();
}

编辑-1:
您还将在此处获得空指针异常

viewholder.artist.setText(data.get(pos).getArtist());

因为您没有在ViewHolder类中初始化artist变量。

编辑-2


@Override
public int getItemCount() {
    return 0;
}

您可以从适配器中删除此特定代码。因为重写我们不使用的类方法有时可能会导致您甚至无法想象的错误。