android - 具有多种 View 类型的 CursorRecyclerViewAdapter

Question

我正在使用来自 this code snippet 的 CursorRecyclerViewAdapter

当我在 recyclerview 中使用 Single Viewtype 时它工作正常。但是如果我使用多个 viewtypes 我会崩溃说 int android.support.v7.widget.RecyclerView$ViewHolder.mItemViewType null object reference/p>

我使用下面的代码来扩展 CursorRecyclerViewAdapter

public class PostCursorAdapter extends CursorRecyclerViewAdapter<RecyclerView.ViewHolder> {

private static final int VIEW_HOLDER_TYPE_1=1;
private static final int VIEW_HOLDER_TYPE_2=2;
private Integer viewtype=0;

public PostCursorAdapter(Context context,Cursor cursor){
    super(context,cursor);

}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, Cursor cursor) {
    PostItem postitem = PostItem.fromCursor(cursor);
    Log.d("PostItem",postitem.toString());
        int viewtype=1;

    if (postitem.isFromMe()==true){
       viewtype=1;
      }
     else {
       viewtype=2;
      }

    switch (viewtype) {

        case VIEW_HOLDER_TYPE_1:
            ViewHolder_Type1 viewholder1 = (ViewHolder_Type1) holder;
            TextView mytimeView = (TextView) viewholder1.mytimeTextView;
            mytimeView.setText(postitem.getPostTime());
            TextView mymsgView = (TextView) viewholder1.mymessageTextView;
            mymsgView.setText(postitem.getPostMsg());
            break;

        case VIEW_HOLDER_TYPE_2:
            ViewHolder_Type2 viewholder2 = (ViewHolder_Type2) holder;
            TextView timeView = (TextView) viewholder2.timeTextView;
            timeView.setText(postitem.getPostTime());
            TextView msgView = (TextView) viewholder2.messageTextView;
            msgView.setText(postitem.getPostMsg());
            break;

        default:
            break;
    }
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v;

    switch (viewType) {

        case VIEW_HOLDER_TYPE_1:
            v = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.mypost, parent, false);
            ViewHolder_Type1 vh1 = new ViewHolder_Type1(v);
            return vh1;

        case VIEW_HOLDER_TYPE_2:
            v = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.post, parent, false);
            ViewHolder_Type2 vh2 = new ViewHolder_Type2(v);
            return vh2;

        default:
            break;
    }

    return null;
}
public static class ViewHolder_Type1 extends RecyclerView.ViewHolder {
    public TextView mymessageTextView, mytimeTextView;
    public ViewHolder_Type1(View v) {
        super(v);
        this.mymessageTextView = (TextView) v.findViewById(R.id.mymessageTextView);
        this.mytimeTextView = (TextView) v.findViewById(R.id.mytimeTextView);
    }


}

public static class ViewHolder_Type2 extends RecyclerView.ViewHolder {
    public TextView messageTextView, timeTextView;
    public ViewHolder_Type2(View v) {
        super(v);
        this.messageTextView = (TextView) v.findViewById(R.id.messageTextView);
        this.timeTextView = (TextView) v.findViewById(R.id.timeTextView);
    }
}}

Answer 1

我是这样解决的

创建一个私有(private) Cursor 并赋值给它

    public PostCursorAdapter(Context context,Cursor cursor){
    super(context,cursor);
    mCursor=cursor;

}

实现getItemViewType

 @Override
public int getItemViewType(int position) {
        if (mCursor.moveToPosition(position))
        {
            PostItem postItem=PostItem.fromCursor(mCursor);
            if (postItem.isFromMe())
            {
                return VIEW_HOLDER_TYPE_1;

            }
            else
            {
                return VIEW_HOLDER_TYPE_2;

            }
        }
    return 1;

}

更改onBindViewHolder

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, Cursor cursor) {
    PostItem postitem = PostItem.fromCursor(cursor);

    switch (getItemViewType(cursor.getPosition())) {

        case VIEW_HOLDER_TYPE_1:
            ViewHolder_Type1 viewholder1 = (ViewHolder_Type1) holder;
            TextView mytimeView = (TextView) viewholder1.mytimeTextView;
            mytimeView.setText(postitem.getPostTime());
            TextView mymsgView = (TextView) viewholder1.mymessageTextView;
            mymsgView.setText(postitem.getPostMsg());
            break;

        case VIEW_HOLDER_TYPE_2:
            ViewHolder_Type2 viewholder2 = (ViewHolder_Type2) holder;
            TextView timeView = (TextView) viewholder2.timeTextView;
            timeView.setText(postitem.getPostTime());
            TextView msgView = (TextView) viewholder2.messageTextView;
            msgView.setText(postitem.getPostMsg());
            break;

        default:
            break;
    }
}