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问题描述

我在使用 RecyclerViewItemTouchHelper 时遇到问题.

I have a problem with ItemTouchHelper of RecyclerView.

我正在制作游戏.游戏板实际上是一个 RecyclerView.RecyclerView 具有 GridLayoutManager 和一些跨度计数.我想实现 drag &丢弃 recyclerview 的项目.任何项目都可以在所有方向(上、下、左、右)上拖动.

I am making a game. The game board is actually a RecyclerView. RecyclerView has GridLayoutManager with some span count. I want to implement drag & drop recyclerview's items. Any item can dragging over all directions (up, down, left, right).

private void initializeLayout() {
    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutFrozen(true);
    recyclerView.setNestedScrollingEnabled(false);

    // set layout manager
    GridLayoutManager layoutManager = new GridLayoutManager(getContext(), BOARD_SIZE,
        LinearLayoutManager.VERTICAL, true);
    recyclerView.setLayoutManager(layoutManager);

    // Extend the Callback class
    ItemTouchHelper.Callback itemTouchCallback = new ItemTouchHelper.Callback() {

    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        Log.w(TAG, "onMove");
        return false;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        // Application does not include swipe feature.
    }

    @Override
    public void onMoved(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder,
                        int fromPos, RecyclerView.ViewHolder target, int toPos, int x, int y) {
        Log.d(TAG, "onMoved");
        // this is calling every time, but I need only when user dropped item, not after every onMove function.
    }

    @Override
    public boolean isItemViewSwipeEnabled() {
        return false;
    }

    @Override
    public boolean isLongPressDragEnabled() {
        return true;
    }

    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.START | ItemTouchHelper.END;
        int swipeFlags = 0;
        return makeMovementFlags(dragFlags, swipeFlags);
    }
    };

    ItemTouchHelper touchHelper = new ItemTouchHelper(itemTouchCallback);
    touchHelper.attachToRecyclerView(recyclerView);
}

SO,当我仍然在 RecyclerView 上拖动项目时,为什么 ItemTouchHelper 的 onMoved 函数起作用?我怎样才能做到这一点?

推荐答案

在拖放项目时,可以多次调用 onMove(),但会调用 clearView() 一次.所以你可以用它来表示拖动结束(发生了下降).并使用两个变量 dragFrom 和 dragTo 来跟踪完成的drag &"中的实际位置.滴".

While dragging and dropping an item, the onMove() can be called more than once, but the clearView() will be called once. So you can use this to indicate the drag was over(drop was happened).And use two variables dragFrom and dragTo to trace the really position in a completed "drag & drop".

private ItemTouchHelper.Callback dragCallback = new ItemTouchHelper.Callback() {

    int dragFrom = -1;
    int dragTo = -1;

    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        return makeMovementFlags(ItemTouchHelper.UP|ItemTouchHelper.DOWN|ItemTouchHelper.LEFT|ItemTouchHelper.RIGHT,
                0);
    }

    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {

        int fromPosition = viewHolder.getAdapterPosition();
        int toPosition = target.getAdapterPosition();


        if(dragFrom == -1) {
            dragFrom =  fromPosition;
        }
        dragTo = toPosition;

        adapter.onItemMove(fromPosition, toPosition);

        return true;
    }

    private void reallyMoved(int from, int to) {
        // I guessed this was what you want...
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {

    }

    @Override
    public boolean isLongPressDragEnabled() {
        return true;
    }

    @Override
    public boolean isItemViewSwipeEnabled() {
        return false;
    }

    @Override
    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        super.clearView(recyclerView, viewHolder);

        if(dragFrom != -1 && dragTo != -1 && dragFrom != dragTo) {
            reallyMoved(dragFrom, dragTo);
        }

        dragFrom = dragTo = -1;
    }

};

adapter.onItemMove(fromPosition, toPosition) 如下所示:

adapter.onItemMove(fromPosition, toPosition) was like below:

public void onItemMove(int fromPosition, int toPosition) {
    list.add(toPosition, list.remove(fromPosition));
    notifyItemMoved(fromPosition, toPosition);
}

这篇关于android - 如何捕捉与 RecyclerView 一起使用的 ItemTouchHelper 的 Drop 动作的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!

07-17 14:54
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