recyclerview 拖拽排序

public class ItemDragCallback  extends ItemTouchHelper.Callback {
    private BleListAdapter mAdapter;
    private boolean mEdit;

    public ItemDragCallback(BleListAdapter mAdapter) {
        this.mAdapter = mAdapter;
    }

    //   该方法返回一个Flags表示Item的三种状态状态：idle(空闲)、 swiping(滑动)、dragging(拖动)，
    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        BleListAdapter adapter = (BleListAdapter) recyclerView.getAdapter();
        mEdit = adapter.isEdit;
        //是否是编辑状态
        if (!mEdit) {
            return 0;
        }
        //拖动支持
        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN|ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
        //滑动支持
        int swipeFlags = 0/**ItemTouchHelper.START | ItemTouchHelper.END**/;
        return makeMovementFlags(dragFlags, swipeFlags);
    }

    // 当ItemTouchHelper拖动一个Item时该方法将会被回调，Item将从旧的位置移动到新的位置，如果不拖动这个方法将从来不会调用,
    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        int fromPosition = viewHolder.getAdapterPosition();   //拖动的position
        int toPosition = target.getAdapterPosition();     //释放的position
        //适配器的方法
        mAdapter.itemMove(fromPosition, toPosition);
        return true;
    }

    //当Item滑动的时候调用，如果不滑动该方法不会被调用，可通过direction做相应的判断执行某些操作。
    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {

    }

    //自定义您的视图如何响应用户交互,如果你不自定义拖动的话这个方法万万不能重写，不然会没动静。实践于（implementation 'com.android.support:recyclerview-v7:28.0.0'）
//    @Override
//    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
//            自定义侧滑菜单
//    }
    //自定义您的视图如何响应用户交互
    @Override
    public void onChildDrawOver(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        super.onChildDrawOver(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
        if (dX != 0 && dY != 0 || isCurrentlyActive) {
            BleListAdapter adapter = (BleListAdapter) recyclerView.getAdapter();
            mEdit = adapter.isEdit;
        }
    }


    @Override
    public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        super.clearView(recyclerView, viewHolder);
        //松手时调用
        int position = viewHolder.getLayoutPosition();
        Log.d("TAG", "clearView: "+"position"+position);
    }
}

public class BleListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    public boolean isEdit = true;//是否是编辑状态

        ......

    /**
     * 对拖拽的元素进行排序
     * @param fromPosition
     * @param toPosition
     */
    void itemMove(int fromPosition, int toPosition) {
        if (fromPosition < toPosition) {
            for (int i = fromPosition; i < toPosition; i++) {
                Collections.swap(mSortedList, i, i + 1);
            }
        } else {
            for (int i = fromPosition; i > toPosition; i--) {
                Collections.swap(mSortedList, i, i - 1);
            }
        }
        notifyItemMoved(fromPosition, toPosition);
    }

      ......  
       
}    

使用

 ItemDragCallback callback = new ItemDragCallback(bleListAdapter);
ItemTouchHelper helper = new ItemTouchHelper(callback);
helper.attachToRecyclerView(rv);