Android recyclerview实现拖拽排序和侧滑删除

Recyclerview现在基本已经替代Listview了，RecyclerView也越来越好用了  当我们有实现条目的拖拽排序和侧滑删除时  可以直接时候Recyclerview提供的API就可以直接实现了
先贴上主要代码

private void initveiw() {
 ArrayList<String> items = new ArrayList<>(Arrays.asList("itme1", "item2", "itme3", "item4", "item5", "item6", "item7", "item8", "itme9", "item10", "itme11", "item12", "item13", "item14", "item15", "item16"));
 recyclerView.setLayoutManager(new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false));
 SimpleAdapter adapter = new SimpleAdapter(items);
 recyclerView.setAdapter(adapter);
 ItemTouchHelper helper = new ItemTouchHelper(new MyItemTouchCallback(adapter));
 helper.attachToRecyclerView(recyclerView);
}

public class MyItemTouchCallback extends ItemTouchHelper.Callback{

private SimpleAdapter adapter;

public MyItemTouchCallback(SimpleAdapter adapter) {
   this.adapter = adapter;
 }

@Override
 public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
   int dragFlag;
   int swipeFlag;
   RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
   if (manager instanceof GridLayoutManager){
     dragFlag = ItemTouchHelper.DOWN | ItemTouchHelper.UP | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
     swipeFlag = 0;
   }else{
     dragFlag = ItemTouchHelper.DOWN | ItemTouchHelper.UP;
     swipeFlag = ItemTouchHelper.END | ItemTouchHelper.START;
   }

return makeMovementFlags(dragFlag,swipeFlag);
 }

@Override
 public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
   int fromPosition = viewHolder.getAdapterPosition();
   int toPosition = target.getAdapterPosition();
   if (fromPosition < toPosition ){
     for (int i = fromPosition ;i<toPosition ;i++){
       Collections.swap(adapter.getDataList(),i,i+1);
     }
   }else{
     for (int i= fromPosition; i>toPosition; i--){
       Collections.swap(adapter.getDataList(),i ,i-1);
     }
   }
   recyclerView.getAdapter().notifyItemMoved(fromPosition,toPosition);
   return true;
 }

@Override
 public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
   int position = viewHolder.getAdapterPosition();
   if (direction == ItemTouchHelper.END | direction==ItemTouchHelper.START){
     adapter.getDataList().remove(position);
     adapter.notifyItemRemoved(position);
   }
 }

@Override
 public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
   super.onSelectedChanged(viewHolder, actionState);
   if (actionState==ItemTouchHelper.ACTION_STATE_DRAG){
     viewHolder.itemView.setBackgroundColor(Color.BLUE);
   }

}

@Override
 public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
   super.clearView(recyclerView, viewHolder);
   viewHolder.itemView.setBackgroundColor(0);
 }
}

步骤：

创建 ItemTouchHelper 对象时候，需要我们传入一个实现了 ItemTouchHelper.Callback 接口的对象。而排序和删除的逻辑都封装在了这个 ItemTouchHelper.Callback 的对象里面了。

private void initveiw() {
 ArrayList<String> items = new ArrayList<>(Arrays.asList("itme1", "item2", "itme3", "item4", "item5", "item6", "item7", "item8", "itme9", "item10", "itme11", "item12", "item13", "item14", "item15", "item16"));
 recyclerView.setLayoutManager(new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false));
 SimpleAdapter adapter = new SimpleAdapter(items);
 recyclerView.setAdapter(adapter);
 ItemTouchHelper helper = new ItemTouchHelper(new MyItemTouchCallback(adapter));
 helper.attachToRecyclerView(recyclerView);
}

 实现ItemTouchHelper.Callback 接口后有三个方法需要重写：

getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) ：设置滑动类型的标记。需要设置两种类型的 flag ，即 dragFlags 和 swipeFlags ，分别代表着拖拽标记和滑动标记。最后需要调用 makeMovementFlags(dragFlags,
 swipeFlags)方法来合成返回。
onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) ：当用户拖拽列表某个 item 时会回调。很明显，拖拽排序的代码应该在这个方法中实现。

onSwiped(RecyclerView.ViewHolder viewHolder, int direction) ：当用户滑动列表某个 item 时会回调。所以侧滑删除的代码应该在这个方法中实现。
下面是重写的几个方法：

第一个，getMovementFlags方法

@Override
public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
 int dragFlag;
 int swipeFlag;
 RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
 if (manager instanceof GridLayoutManager){
   dragFlag = ItemTouchHelper.DOWN | ItemTouchHelper.UP | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
   swipeFlag = 0;
 }else{
   dragFlag = ItemTouchHelper.DOWN | ItemTouchHelper.UP;
   swipeFlag = ItemTouchHelper.END | ItemTouchHelper.START;
 }

return makeMovementFlags(dragFlag,swipeFlag);
}

这个方法里面根据LayoutManager分了两种情况，根据自己的情况去分
在GridLayoutManager中只能上下左右拖拽但是不能侧滑删除，所以swipFlag = 0；swipeFlag的值ItemTouchHelper.END是右滑删除，ItemTouchHelper.START是左滑删除
最后调用makeMovementFlags方法合成返回

第二个，onMove方法

@Override
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
 int fromPosition = viewHolder.getAdapterPosition();
 int toPosition = target.getAdapterPosition();
 if (fromPosition < toPosition ){
   for (int i = fromPosition ;i<toPosition ;i++){
     Collections.swap(adapter.getDataList(),i,i+1);
   }
 }else{
   for (int i= fromPosition; i>toPosition; i--){
     Collections.swap(adapter.getDataList(),i ,i-1);
   }
 }
 recyclerView.getAdapter().notifyItemMoved(fromPosition,toPosition);
 return true;
}

这个方法是用户在拖拽 item 的时候调用。所以关于列表排序的代码应该写在这里。方法参数中的 viewHolder 代表的是用户当前拖拽的 item ，而 target 代表的是被用户拖拽所覆盖的那个 item 。所以在 onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) 方法中的逻辑就是把 fromPosition 至 toPosition 为止改变它们的位置。

第三个，onSwiped方法

@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
 int position = viewHolder.getAdapterPosition();
 if (direction == ItemTouchHelper.END | direction==ItemTouchHelper.START){
   adapter.getDataList().remove(position);
   adapter.notifyItemRemoved(position);
 }
}

这个方法是在用户侧滑的时候调用的 ，在里面对adapter的数据进行删除就可以了

最后两个方法

@Override
 public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
   super.onSelectedChanged(viewHolder, actionState);
   if (actionState==ItemTouchHelper.ACTION_STATE_DRAG){
     viewHolder.itemView.setBackgroundColor(Color.BLUE);
   }

}

@Override
 public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
   super.clearView(recyclerView, viewHolder);
   viewHolder.itemView.setBackgroundColor(0);
 }
}

就是优化的方法，第一个是选择条目改变状态，第二个是手指抬起之后恢复条目状态