Android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<MyAdapter.MyViewHolder> 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);
  }

}