還記得之前我們對RecycyleView的項目，實現了上下拖曳的實作。
那麼今天來實作左右滑動吧

我們一樣需要三項物件

• class ItemTouchHelperCallback extends ItemTouchHelper.Callback
• interface ItemTouchHelperAdapter
• class recycleViewAdapter

那麼一樣先宣告一個class 繼承 ItemTouchHelper.Callback

public class ItemTouchHelperCallback extends ItemTouchHelper.Callback {

    private ItemTouchHelperAdapter mAdapter;

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

    @Override
    public int getMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
        int swipeFlags = ItemTouchHelper.LEFT|ItemTouchHelper.RIGHT;
        return makeMovementFlags(dragFlags, swipeFlags);
    }

    @Override
    public boolean isLongPressDragEnabled() {
        return true;
    }

    @Override
    public boolean isItemViewSwipeEnabled() {
        return true;
    }

    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        mAdapter.onItemMove(viewHolder.getAdapterPosition(), target.getAdapterPosition());
        return true;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        mAdapter.onItemDissmiss(viewHolder.getAdapterPosition());
    }
}

一樣getMovementFlags函式可以指定項目移動的方向

int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
指定拖曳方向往上還是往下，使用|符號表示兩者任一都成立
int swipeFlags = ItemTouchHelper.LEFT| ItemTouchHelper.RIGHT;
指定滑動方向往左還是往右，使用|符號表示兩者任一都成立
這邊設定

int swipeFlags = ItemTouchHelper.LEFT| ItemTouchHelper.RIGHT;

這邊要注意的是，isItemViewSwipeEnabled要設定為true

@Override
public boolean isItemViewSwipeEnabled() {
    return true;
}

一樣宣告一個interfece 來作為 RecycleView Adapter與ItemTouchHelper.Callback的接口

interface ItemTouchHelperAdapter {
    fun onItemMove( fromPosition : Int, toPosition :Int)
    fun onItemDissmiss(position: Int)
}

一樣接下來實作RecyclerView.Adapter

open class recycleViewAdapter(val context: Context, val recordList: MutableList<String>
) :
    RecyclerView.Adapter<recycleViewAdapter.ViewHolder>()
    , ItemTouchHelperAdapter
{

    lateinit var mViewHolder : recycleViewAdapter.ViewHolder
    override fun onItemDissmiss(position: Int) {
        recordList.removeAt(position)
        notifyItemRemoved(position)
    }

    override fun onItemMove(fromPosition: Int, toPosition: Int) {
        Collections.swap(recordList,fromPosition,toPosition)
        notifyItemMoved(fromPosition,toPosition)
    }
 ...
 }

到這邊左右滑動就實作完成了