android - 如何正确处理 recyclerView 上的滑动删除？

Question

背景

我试图允许滑动以删除回收站 View 中的项目，但出于某种原因，它并不总是很好地播放，显示空白而不是卡片。

我已经让代码处理甩动和移动项目，以触发滑动动画，当滑动动画结束时，项目将从数据集中删除并通知适配器。

可能是因为我是 RecyclerView 的新手，但我找不到缺少的东西。

代码

 public class MainActivity extends ActionBarActivity
    {
    private RecyclerView mRecyclerView;
    private LinearLayoutManager mLayoutManager;
    private MyAdapter mAdapter;
    private static final int DATA_COUNT=100;
    private ArrayList<String> mDataSet;

    @Override
    protected void onCreate(final Bundle savedInstanceState)
      {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      mRecyclerView=(RecyclerView)findViewById(R.id.my_recycler_view);
      mRecyclerView.setHasFixedSize(true);
      mLayoutManager=new LinearLayoutManager(this);
  // TODO in case we use GridLayoutManager, consider using this: http://stackoverflow.com/q/26869312/878126
      mRecyclerView.setLayoutManager(mLayoutManager);
      mDataSet=new ArrayList<String>(DATA_COUNT);
      for(int i=0;i<DATA_COUNT;++i)
        mDataSet.add(Integer.toString(i));
      mAdapter=new MyAdapter(mDataSet);
      mRecyclerView.setAdapter(mAdapter);
      }

    // ///////////////////////////////////////////////////////////////
  // MyAdapter//
  // ///////////
    public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>
      {
      private final ArrayList<String> mDataset;

      public class ItemViewType
        {
        private static final int HEADER=0, ITEM=1;
        }

      public MyAdapter(final ArrayList<String> myDataset)
        {
        mDataset=myDataset;
        }

      @Override
      public RecyclerView.ViewHolder onCreateViewHolder(final ViewGroup parent,final int viewType)
        {
        final RecyclerView.ViewHolder holder;
        final View rootView;
        switch(viewType)
          {
          case ItemViewType.HEADER:
            rootView=LayoutInflater.from(parent.getContext()).inflate(R.layout.header,parent,false);
            holder=new HeaderViewHoler(rootView);
            break;
          case ItemViewType.ITEM:
            rootView=LayoutInflater.from(parent.getContext()).inflate(R.layout.card,parent,false);
            holder=new ItemViewHolder(rootView);
            rootView.setAlpha(1);
            rootView.setTranslationX(0);
            rootView.setTranslationY(0);
            handleSwiping(rootView,holder);
            break;
          default:
            holder=null;
            break;
          }
        return holder;
        }

      private void handleSwiping(final View rootView,final RecyclerView.ViewHolder holder)
        {
        final GestureDetectorCompat gestureDetector=new GestureDetectorCompat(rootView.getContext(),
            new GestureDetector.OnGestureListener()
            {
            ...      
            @Override
            public boolean onFling(final MotionEvent e1,final MotionEvent e2,final float velocityX,
                                   final float velocityY)
              {
              final int viewSwipeThreshold=rootView.getWidth()/4;
              if(velocityX<-viewSwipeThreshold)
                {
                onSwipe(rootView,holder.getPosition(),false);
                return true;
                }
              else if(velocityX>viewSwipeThreshold)
                {
                onSwipe(rootView,holder.getPosition(),true);
                return true;
                }
              return false;
              }
            });
        rootView.setOnTouchListener(new View.OnTouchListener()
        {
        private final float originalX=0;
        private final float originalY=0;
        private float startMoveX=0;
        private float startMoveY=0;

        @Override
        public boolean onTouch(final View view,final MotionEvent event)
          {
          final int viewSwipeHorizontalThreshold=rootView.getWidth()/3;
          final int viewSwipeVerticalThreshold=view.getContext().getResources()
              .getDimensionPixelSize(R.dimen.vertical_swipe_threshold);
          if(gestureDetector.onTouchEvent(event))
            return true;
          final float x=event.getRawX(), y=event.getRawY();
          final float deltaX=x-startMoveX, deltaY=y-startMoveY;
          switch(event.getAction()&MotionEvent.ACTION_MASK)
            {
            case MotionEvent.ACTION_DOWN:
              startMoveX=x;
              startMoveY=y;
              break;
            case MotionEvent.ACTION_UP:
              if(Math.abs(deltaX)<viewSwipeHorizontalThreshold)
                {
                rootView.animate().translationX(originalX).translationY(originalY).alpha(1).start();
                if(Math.abs(deltaY)<viewSwipeHorizontalThreshold)
                  rootView.performClick();
                }
              else if(deltaX<0)
                onSwipe(rootView,holder.getPosition(),true);
              else
                onSwipe(rootView,holder.getPosition(),false);
              break;
            case MotionEvent.ACTION_CANCEL:
              if(Math.abs(deltaX)<viewSwipeHorizontalThreshold
                  ||Math.abs(deltaY)<viewSwipeVerticalThreshold)
                rootView.animate().translationX(originalX).translationY(originalY).alpha(1).start();
              else if(deltaX<0)
                onSwipe(rootView,holder.getPosition(),true);
              else
                onSwipe(rootView,holder.getPosition(),false);
              break;
            case MotionEvent.ACTION_POINTER_DOWN:
              break;
            case MotionEvent.ACTION_POINTER_UP:
              break;
            case MotionEvent.ACTION_MOVE:
              rootView.setAlpha(Math.max(Math.min((255-Math.abs(deltaX))/255f,1.0f),0.1f));
              rootView.setTranslationX(deltaX);
              break;
            }
          return true;
          }
        });

        }

      @Override
      public void onBindViewHolder(final RecyclerView.ViewHolder holder,final int position)
        {
        final int itemViewType=getItemViewType(position);
        final View rootView=holder.itemView;
        rootView.setAlpha(1);
        rootView.setTranslationX(0);
        rootView.setTranslationY(0);
        }

      private void onSwipe(final View rootView,final int position,final boolean isToLeft)
        {
        ViewPropertyAnimator animator;
        if(isToLeft)
          animator=rootView.animate().translationX(-rootView.getWidth());
        else
          animator=rootView.animate().translationX(rootView.getWidth());
        animator.setListener(new Animator.AnimatorListener()
        {
        @Override
        public void onAnimationStart(Animator animation)
          {
          }

        @Override
        public void onAnimationEnd(Animator animation)
          {
          rootView.setAlpha(1);
          mDataset.remove(position);
          notifyItemRemoved(position);
          }

        @Override
        public void onAnimationCancel(Animator animation)
          {
          }

        @Override
        public void onAnimationRepeat(Animator animation)
          {
          }
        });
        animator.start();
        }

      @Override
      public int getItemCount()
        {
        return mDataset.size()+1;
        }

      @Override
      public int getItemViewType(final int position)
        {
        return position==0?ItemViewType.HEADER:ItemViewType.ITEM;
        }
      }

  // ///////////////////////////////////////
  // HeaderViewHoler //
  // //////////////////

    public static class HeaderViewHoler extends RecyclerView.ViewHolder
      {
      public TextView mTextView;

      public HeaderViewHoler(final View v)
        {
        super(v);
        }
      }

    // ///////////////////////////////////////
  // ItemViewHolder //
  // /////////////////
    public static class ItemViewHolder extends RecyclerView.ViewHolder
      {

      public ItemViewHolder(final View rootView)
        {
        super(rootView);
        rootView.setAlpha(1);
        rootView.setTranslationX(0);
        rootView.setTranslationY(0);
        }
      }
    }

问题

我做的有什么问题吗？为什么有时好有时不好？

滑动删除处理是否有更好的解决方案？

Answer 1

您不能在回调中访问 position 参数，因为 RecyclerView 不会仅仅因为其位置已更改就重新绑定(bind) ViewHolder。删除一个项目会更改其下方所有项目的位置，因此您对这些项目的所有位置引用都将过时。

相反，您可以使用 ViewHolder#getPosition 获取用户操作时的最新位置。

除此之外，不要在onBind中添加手势监听器和触摸监听器，而是在创建ViewHolder时添加它们。这样，您将避免在每次弹回项目时都创建一个新对象。

评论更新。建议的更改:

@Override
    public RecyclerView.ViewHolder onCreateViewHolder(final ViewGroup parent, final int viewType) {
        RecyclerView.ViewHolder holder = null;
        View rootView;
        switch (viewType) {
        case ItemViewType.HEADER:
            rootView = LayoutInflater.from(parent.getContext()).inflate(R.layout.header, parent, false);
            holder = new HeaderViewHoler(rootView);
            break;
        case ItemViewType.ITEM:
            rootView = LayoutInflater.from(parent.getContext()).inflate(R.layout.card, parent, false);
            holder = new ItemViewHolder(rootView);
            //initialize gesture detector and touch listener, replace position with getPosiiton
        }
        return holder;
    }