RecyclerView通过itemTouchHelper拖放快速拖动时很奇怪

Question

我一直在关注此链接"Drag and Swipe with RecyclerView - by IPaulPro" 的指南，在某些情况下我遇到了一些问题。

所以，我基本上做了他解释的所有事情 + 我在 item 中添加了一个 TextView，它表示 RecyclerView 中 item 的位置，如下所示：

一切看起来都不错，除非我开始快速“弹射”物品，然后我有两个问题：

1. 它恰好有重复的数字。

   我所做的是在 onItemClear() 方法 - 它以某种方式修复它，但导致 IllegalStateException，抓住了 - 会导致 IndexOutOfBounds 异常。

2. 有时，当滑动过快时，项目会进入“背景”。仅当项目大小不同时才能看到这一点。

我将把我的整个适配器代码粘贴在下面，其中一定有缺陷。

LayoutInflater inflater;
Context context;
AndroidEntityQuestionResult androidEntityQuestionResult;
ArrayList<AndroidEntityAnswer> list = new ArrayList<>();
ORDLayoutManagerQuestion ord;
ScreenDimensionsConstants sdc;


public OrderingRecycleAdapter(Context context, AndroidEntityQuestionResult androidEntityQuestionResult, ORDLayoutManagerQuestion ord) {
    inflater = LayoutInflater.from(context);
    this.context = context;
    this.list = androidEntityQuestionResult.getAndroidEntityQuestion().getEntityAnswer();
    this.androidEntityQuestionResult = androidEntityQuestionResult;
    this.ord = ord;
    sdc = new ScreenDimensionsConstants(context);
}

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = inflater.inflate(R.layout.custom_row_ordering_rv, parent, false);
    final RecyclerView.ViewHolder holder = new OrderingViewHolder(view);
    return holder;
}


@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    if (holder instanceof OrderingViewHolder) {

        ((OrderingViewHolder) holder).answerText.setText(list.get(position).getAnswer().getANSWER_TEXT());
        int currentPosition = position + 1;
        ((OrderingViewHolder) holder).position.setText("#" + currentPosition);
    }
}

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

@Override
public boolean onItemMove(int fromPosition, int toPosition) {
    if (fromPosition < toPosition) {
        for (int i = fromPosition; i < toPosition; i++) {
            Collections.swap(list, i, i + 1);
        }
    } else {
        for (int i = fromPosition; i > toPosition; i--) {
            Collections.swap(list, i, i - 1);
        }
    }
    notifyItemMoved(fromPosition, toPosition);
    notifyItemChanged(fromPosition);
    return true;
}

@Override
public void onItemDismiss(int position) {

}

@Override
public void onStartDrag(RecyclerView.ViewHolder viewHolder) {
        ord.getItemTouchHelper().startDrag(viewHolder);
}

class OrderingViewHolder extends RecyclerView.ViewHolder implements ItemTouchHelperViewHolder {
    private TextView answerText;
    private ImageView pin;
    private TextView position;

    public OrderingViewHolder(View itemView) {
        super(itemView);
        answerText = (TextView) itemView.findViewById(R.id.orderingAnswer);
        answerText.setTextSize(TypedValue.COMPLEX_UNIT_PX, sdc.getHeight() / 40);

        pin = (ImageView) itemView.findViewById(R.id.ordering_pin);
        pin.getLayoutParams().width = sdc.getHeight() / 15;
        pin.getLayoutParams().height = sdc.getHeight() / 15;

        pin.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (MotionEventCompat.getActionMasked(event) ==
                        MotionEvent.ACTION_DOWN) {
                    OrderingRecycleAdapter.this.onStartDrag(OrderingViewHolder.this);
                }
                return false;
            }
        });
        position = (TextView) itemView.findViewById(R.id.answer_position);
        position.setTextSize(TypedValue.COMPLEX_UNIT_PX, sdc.getHeight() / 40);

    }

    @Override
    public void onItemSelected() {
        itemView.setBackgroundResource(R.drawable.menu_item_background_ice_blue);
    }

    @Override
    public void onItemClear() {
        itemView.setBackgroundResource(R.drawable.menu_item_background_white);
        int currentPosition = getLayoutPosition() + 1;
        position.setText("#" + currentPosition);
       //notifyDataSetChanged();

    }
}

额外问题

是否有任何与 2 个 RecyclerView 之间的拖放相关的教程或任何信息？

我知道有一个关于 SO 的问题，但没有答案，我在这里可能更幸运。

Answer 1

改变你的 onitemmove 方法

@Override
public boolean onItemMove(int fromPosition, int toPosition) {
    if (fromPosition < toPosition) {
        for (int i = fromPosition; i < toPosition; i++) {
            Collections.swap(list, i, i + 1);
        }
    } else {
        for (int i = fromPosition; i > toPosition; i--) {
            Collections.swap(list, i, i - 1);
        }
    }
    notifyItemMoved(fromPosition, toPosition);
    notifyItemChanged(fromPosition);
    return true;
}

到：

@Override
public boolean onItemMove(int fromPosition, int toPosition) {
    if (fromPosition < toPosition) {
        for (int i = fromPosition; i < toPosition; i++) {
            Collections.swap(list, i, i + 1);
        }
    } else {
        for (int i = fromPosition; i > toPosition; i--) {
            Collections.swap(list, i, i - 1);
        }
    }
    notifyItemMoved(fromPosition, toPosition);
    return true;
}

Answer 2

在我看来，您的 onItemMove() 似乎并没有考虑到所有的变化。 当某物移动不止一个项目时（假设在 A 和 B 之间），您正在交换两者之间的所有项目。 但是，您只向 A 和 B 报告更改，而不向其间的其他元素报告。

我建议你写一个交换方法来报告所有的变化：

public boolean swapItems(int fromPosition, int toPosition){
    Collections.swap(list, fromPosition, toPosition);
    notifyItemMoved(fromPosition, toPosition);
    notifyItemMoved(toPosition, fromPosition);
    // And maybe also notifyItemChanged() as the item changes due to the shift
    notifyItemChanged(fromPosition);
    notifyItemChanged(toPosition);
}

调用此函数而不是 Collections.swap() 并删除其余的通知代码。

Answer 3

我知道它已经晚了，因为我看不到正确的答案在这里发布答案。只需在返回 true 之前添加notifyItemRangeChanged(fromPosition,toPosition)。

notifyItemChanged(fromPosition);
notifyItemMoved(fromPosition, toPosition);
notifyItemRangeChanged(fromPosition,toPosition)