Android如何使用RecycleView实现拖拽交换item位置

public void attachToRecyclerView(@Nullable RecyclerView recyclerView) {}

//决定拖拽/滑动的方向
public abstract int getMovementFlags(RecyclerView recyclerView,
    ViewHolder viewHolder);

//和位置交换有关,可用于实现drag功能
public abstract boolean onMove(RecyclerView recyclerView,
    ViewHolder viewHolder, ViewHolder target);

//和滑动有关,可用于实现swipe功能
public abstract void onSwiped(ViewHolder viewHolder, int direction);

//是否长按启用拖拽功能,默认是true
public boolean isLongPressDragEnabled() {return true;}

//是否支持滑动,默认true
public boolean isItemViewSwipeEnabled() {return true;}

//和目标View的状态改变有关,例如drag,swipe,ide
public void onSelectedChanged(ViewHolder viewHolder, int actionState) {}

//和移除View的状态有关,通常用于清除在onSelectedChanged,onChildDraw中对View设置的动画
public void clearView(RecyclerView recyclerView, ViewHolder viewHolder) {}

/**
 * 定义RecycleView的Adapter和SimpleItemTouchHelperCallback直接交互的接口方法
 * Created by mChenys on 2017/2/16.
 */
public interface ItemTouchHelperAdapter {

 //数据交换
 void onItemMove(RecyclerView.ViewHolder source, RecyclerView.ViewHolder target);

 //数据删除
 void onItemDissmiss(RecyclerView.ViewHolder source);

 //drag或者swipe选中
 void onItemSelect(RecyclerView.ViewHolder source);

 //状态清除
 void onItemClear(RecyclerView.ViewHolder source);
}

/**
 * 处理RecycleView的选中,拖拽移动,拖拽删除的实现类
 * Created by mChenys on 2017/2/16.
 */
public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {

 private ItemTouchHelperAdapter mAdapter;

 public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter) {
  mAdapter = adapter;
 }

 @Override
 public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
  //int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN; //允许上下的拖动
  //int dragFlags =ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT; //允许左右的拖动
  //int swipeFlags = ItemTouchHelper.LEFT; //只允许从右向左侧滑
  //int swipeFlags = ItemTouchHelper.DOWN; //只允许从上向下侧滑
  //一般使用makeMovementFlags(int,int)或makeFlag(int, int)来构造我们的返回值
  //makeMovementFlags(dragFlags, swipeFlags)

  int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT; //允许上下左右的拖动
  return makeMovementFlags(dragFlags, 0);
 }

 @Override
 public boolean isLongPressDragEnabled() {
  return true;//长按启用拖拽
 }

 @Override
 public boolean isItemViewSwipeEnabled() {
  return false; //不启用拖拽删除
 }

 @Override
 public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder source, RecyclerView.ViewHolder target) {
  //通过接口传递拖拽交换数据的起始位置和目标位置的ViewHolder
  mAdapter.onItemMove(source, target);
  return true;
 }


 @Override
 public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
  //移动删除回调,如果不用可以不用理
  // mAdapter.onItemDissmiss(viewHolder);
 }

 @Override
 public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
  super.onSelectedChanged(viewHolder, actionState);
  if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
   //当滑动或者拖拽view的时候通过接口返回该ViewHolder
   mAdapter.onItemSelect(viewHolder);
  }
 }

 @Override
 public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
  super.clearView(recyclerView, viewHolder);
  if (!recyclerView.isComputingLayout()) {
   //当需要清除之前在onSelectedChanged或者onChildDraw,onChildDrawOver设置的状态或者动画时通过接口返回该ViewHolder
   mAdapter.onItemClear(viewHolder);
  }
 }
}

/**
 * Created by mChenys on 2017/2/15.
 */
public class MyAdapter extends RecyclerView.Adapter implements ItemTouchHelperAdapter {
 ...

 @Override
 public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
  ...
 }

 @Override
 public void onBindViewHolder(final MyAdapter.MyViewHolder holder, int position) {
  ...
 }

 @Override
 public int getItemCount() {
  //注意:这里最少有一个,因为有多了一个添加按钮
  return null == mData ? 1 : mData.size() + 1;
 }

 @Override
 public void onItemMove(RecyclerView.ViewHolder source,
  RecyclerView.ViewHolder target) {
  int fromPosition = source.getAdapterPosition();
  int toPosition = target.getAdapterPosition();
  if (fromPosition < mData.size() && toPosition < mData.size()) {
   //交换数据位置
   Collections.swap(mData, fromPosition, toPosition);
   //刷新位置交换
   notifyItemMoved(fromPosition, toPosition);
  }
  //移动过程中移除view的放大效果
  onItemClear(source);
 }

 @Override
 public void onItemDissmiss(RecyclerView.ViewHolder source) {

  int position = source.getAdapterPosition();
  mData.remove(position); //移除数据
  notifyItemRemoved(position);//刷新数据移除
 }

 @Override
 public void onItemSelect(RecyclerView.ViewHolder viewHolder) {

  //当拖拽选中时放大选中的view
  viewHolder.itemView.setScaleX(1.2f);
  viewHolder.itemView.setScaleY(1.2f);
 }

 @Override
 public void onItemClear(RecyclerView.ViewHolder viewHolder) {

  //拖拽结束后恢复view的状态
  viewHolder.itemView.setScaleX(1.0f);
  viewHolder.itemView.setScaleY(1.0f);
 }

 public class MyViewHolder extends RecyclerView.ViewHolder {
  ...

  public MyViewHolder(View itemView) {
   super(itemView);
   ...
  }
 }

}

/**
 * Created by mChenys on 2017/2/16.
 */
public class MainActivity extends AppCompatActivity {
 ...
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  ...
  mRecyclerView = (RecyclerView) findViewById(R.id.recycleView);
  //创建adapter
  MyAdapter myAdapter = new MyAdapter(this, mData);
  //设置默认的布局方式
  mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
  //设置adapter
  mRecyclerView.setAdapter(myAdapter);
  //创建SimpleItemTouchHelperCallback
  ItemTouchHelper.Callback callback = new SimpleItemTouchHelperCallback(myAdapter);
  //用Callback构造ItemtouchHelper
  ItemTouchHelper touchHelper = new ItemTouchHelper(callback); 
  //调用ItemTouchHelper的attachToRecyclerView方法建立联系
  touchHelper.attachToRecyclerView(mRecyclerView);
 }



 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  ...
  return super.onCreateOptionsMenu(menu);
 }

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
  ...
  return super.onOptionsItemSelected(item);
 }

}