01_RecyclerView实现列表Item长按移动、左右滑动删除

原创已于 2023-08-14 08:53:13 修改 · 1.7k 阅读

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#ItemTouchHelper #RecyclerView #Item长按移动 #List左右滑动删除

于 2017-07-03 17:02:38 首次发布

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本文介绍如何使用ItemTouchHelper实现RecyclerView的滑动删除和拖拽功能。具体包括不同布局下拖拽方向的设置、数据交换逻辑及UI效果调整等。

安卓基础总结

Demo地址：

#1 Introduce

ItemTouchHelper是一个处理RecyclerView的滑动删除和拖拽的辅助类，RecyclerView 的item拖拽移动和滑动删除就靠它来实现。

#2 效果图

#3 关键代码ItemTouchHelper

ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new ItemTouchHelper.Callback() {
@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
int dragFlags=0,swipeFlags=0;
if(recyclerView.getLayoutManager() instanceof StaggeredGridLayoutManager ||recyclerView.getLayoutManager() instanceof GridLayoutManager){
//网格式布局有4个方向
dragFlags=ItemTouchHelper.UP|ItemTouchHelper.DOWN|ItemTouchHelper.LEFT|ItemTouchHelper.RIGHT;
}else if(recyclerView.getLayoutManager() instanceof LinearLayoutManager){
//线性式布局有2个方向
dragFlags=ItemTouchHelper.UP|ItemTouchHelper.DOWN;
swipeFlags = ItemTouchHelper.START|ItemTouchHelper.END; //设置侧滑方向为从两个方向都可以
}
return makeMovementFlags(dragFlags,swipeFlags);//swipeFlags 为0的话item不滑动
}

@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
int from=viewHolder.getAdapterPosition();
int to=target.getAdapterPosition();

String moveItem = list.get(from);
list.remove(from);
list.add(to,moveItem);//交换数据链表中数据的位置

adapter.notifyItemMoved(from,to);//更新适配器中item的位置
return true;
}

@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
int from=viewHolder.getAdapterPosition();
list.remove(list.get(from));
adapter.notifyItemRemoved(from);
}

@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
super.onSelectedChanged(viewHolder, actionState);
if(actionState==ItemTouchHelper.ACTION_STATE_DRAG){
viewHolder.itemView.setBackgroundColor(Color.LTGRAY);//拖拽时设置背景色为灰色
}
}

@Override
public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
super.clearView(recyclerView, viewHolder);
viewHolder.itemView.setBackgroundColor(getResources().getColor(R.color.colorPrimary));//拖拽停止时设置背景色为白色
}

@Override
public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
//根据item滑动偏移的值修改item透明度。screenwidth是我提前获得的屏幕宽度
viewHolder.itemView.setAlpha(1-Math.abs(dX)/viewHolder.itemView.getWidth());
}
});

itemTouchHelper.attachToRecyclerView(rv);