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

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