android-如何捕获与RecyclerView一起使用的ItemTouchHelper的放置动作 [英] android - how to catch Drop action of ItemTouchHelper which is used with RecyclerView

问题描述

我在 RecyclerView 的 ItemTouchHelper 上遇到问题.

我在做游戏.游戏板实际上是RecyclerView. RecyclerView具有 GridLayoutManager ，并具有一定的跨度计数.我要实施拖动&删除 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);
}

所以，为什么当我仍然在RecyclerView上拖动项目时，为什么ItemTouchHelper的onMoved函数起作用?我该如何实现?

推荐答案

在拖放项目时，可以多次调用onMove()，但将调用一次clearView().因此，您可以使用它来指示拖动已结束(发生了掉落). 并使用两个变量dragFrom和dragTo来跟踪完成的拖放"中的实际位置.

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:

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

list.add(toPosition, list.remove(fromPosition)); notifyItemMoved(fromPosition, toPosition);

list.add(toPosition, list.remove(fromPosition)); notifyItemMoved(fromPosition, toPosition);

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