ItemTouchHelper

ItemTouchHelper用于RecyclerView项的滑动、拖动控制。首先创建RecyclerView和Adapter，这个写法与以前写法相同。

滑动删除/拖动交换位置

//第一个参数为可拖动方向，第而个参数为可滑动方向
new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP | ItemTouchHelper.DOWN, 
ItemTouchHelper.LEFT) {
    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView
            .ViewHolder target) {        
        int fromPosition = viewHolder.getAdapterPosition();//得到拖动ViewHolder的position
        int toPosition = target.getAdapterPosition();//得到目标ViewHolder的position
        if (fromPosition < toPosition) {
            //分别把中间所有的item的位置重新交换
            for (int i = fromPosition; i < toPosition; i++) {
                Collections.swap(strings, i, i + 1);
            }
        } else {
            for (int i = fromPosition; i > toPosition; i--) {
                Collections.swap(strings, i, i - 1);
            }
        }
        touchAdapter.notifyItemMoved(fromPosition, toPosition);
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        int position = viewHolder.getAdapterPosition();
        strings.remove(position);
        touchAdapter.notifyItemRemoved(position);
    }
}).attachToRecyclerView(rv);

方向分别有6种

ItemTouchHelper.DOWN
ItemTouchHelper.LEFT
ItemTouchHelper.RIGHT
ItemTouchHelper.START
ItemTouchHelper.END

默认情况下长按可拖动改变位置，如果想直接拖动某控件改变位置的话可以
先重写ItemTouchHelper的禁用长按拖动

public boolean isLongPressDragEnabled() {
    return false;
}

然后添加以下代码

viewHolder.dragButton.setOnTouchListener(new View.OnTouchListener() {
   public boolean onTouch(View v, MotionEvent event) {
       if (MotionEventCompat.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
           mItemTouchHelper.startDrag(viewHolder);
       }
       return false;
   }
});

其他方法

@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
    super.onSelectedChanged(viewHolder, actionState);
    switch (actionState) {
        case ItemTouchHelper.ACTION_STATE_IDLE:
            Log.e("ACTION_STATE_IDLE", "ACTION_STATE_IDLE");
            //空闲状态
            break;
        case ItemTouchHelper.ACTION_STATE_SWIPE:
            //滑动状态
            Log.e("ACTION_STATE_SWIPE", "ACTION_STATE_SWIPE");
            break;
        case ItemTouchHelper.ACTION_STATE_DRAG:
            Log.e("ACTION_STATE_DRAG", "ACTION_STATE_DRAG");
            //拖动状态
            break;
    }
}
@Override
public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
    super.clearView(recyclerView, viewHolder);
    //拖动完成
}

@Override
public boolean isItemViewSwipeEnabled() {
    //启用滑动
    return super.isItemViewSwipeEnabled();
}
@Override
public void onMoved(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, int fromPos, 
                    RecyclerView.ViewHolder target, int toPos, int x, int y) {
    super.onMoved(recyclerView, viewHolder, fromPos, target, toPos, x, y);
}
@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
    //和SimpleCallback构造函数参数意思相同
    int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
    int swipeFlags = ItemTouchHelper.RIGHT;
    return makeMovementFlags(dragFlags, swipeFlags);
}