RecycleView实现侧滑删除item

对于列表空间的侧滑操作，网上有很多开源的空间可以使用，Google在它的新控件RecycleView中增加了侧滑的API,完全遵循Material Design设计规范，下面看看效果演示：

下面看看介绍一下刷新控制类：  ItemTouchHelper。

顾名思义，这个类就是来帮助我们对于item执行更多的操作。下面看看具体操作：

我们实例化这个类的时候需要传入对应的会掉接口：

/**
     * Creates an ItemTouchHelper that will work with the given Callback.
     * <p>
     * You can attach ItemTouchHelper to a RecyclerView via
     * {@link #attachToRecyclerView(RecyclerView)}. Upon attaching, it will add an item decoration,
     * an onItemTouchListener and a Child attach / detach listener to the RecyclerView.
     *
     * @param callback The Callback which controls the behavior of this touch helper.
     */
    public ItemTouchHelper(Callback callback) {
        mCallback = callback;
    }

看源码会发现这个接口是个抽象类，我们看看ItemTouchHelper中写了一个抽象类继承与该抽象类：

  /**
         * Creates a Callback for the given drag and swipe allowance. These values serve as
         * defaults
         * and if you want to customize behavior per ViewHolder, you can override
         * {@link #getSwipeDirs(RecyclerView, ViewHolder)}
         * and / or {@link #getDragDirs(RecyclerView, ViewHolder)}.
         *
         * @param dragDirs  Binary OR of direction flags in which the Views can be dragged. Must be
         *                  composed of {@link #LEFT}, {@link #RIGHT}, {@link #START}, {@link
         *                  #END},
         *                  {@link #UP} and {@link #DOWN}.
         * @param swipeDirs Binary OR of direction flags in which the Views can be swiped. Must be
         *                  composed of {@link #LEFT}, {@link #RIGHT}, {@link #START}, {@link
         *                  #END},
         *                  {@link #UP} and {@link #DOWN}.
         */
        public SimpleCallback(int dragDirs, int swipeDirs) {
            mDefaultSwipeDirs = swipeDirs;
            mDefaultDragDirs = dragDirs;
        }

在实现了它的适合需要传入两个参数，一个是拖出来的方向以及滑动的方向，通常我们只需要指定后者的参数，前置置为0即可。以下是可选参数。

 /**
     * Up direction, used for swipe & drag control.
     */
    public static final int UP = ;

    /**
     * Down direction, used for swipe & drag control.
     */
    public static final int DOWN =  << ;

    /**
     * Left direction, used for swipe & drag control.
     */
    public static final int LEFT =  << ;

    /**
     * Right direction, used for swipe & drag control.
     */
    public static final int RIGHT =  << ;

当我们实现了这个抽象类之后需要复写它的三个方法，当然也可以继承于它。接下来是具体实现代码。

 ItemTouchHelper touchHelper = new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
            @Override
            public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
                //滑动时的一些操作
                isDelete = false;
                return true;
            }

            @Override
            public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
                // 处理滑动事件回调
                final int pos = viewHolder.getAdapterPosition();
                ImActiveChat imActiveChat = imActiveChatList.get(pos);
                imActiveChatList.remove(pos);
                chatRVAdapter.notifyItemRemoved(pos);
                if (imActiveChatList.size()==0){
                    rvSingleChat.setVisibility(View.GONE);
                    tvNoMessage.setVisibility(View.VISIBLE);

                }
                String text;
                isDelete = true;
                // 判断方向，进行不同的操作
                if (direction == ItemTouchHelper.RIGHT) {

                    text = "删除了和" + imActiveChat.getUserId() + "的聊天";

                } else {

                    text = "删除了和" + imActiveChat.getUserId() + "的聊天";
                }

                Snackbar.make(viewHolder.itemView, text, Snackbar.LENGTH_SHORT)

                        .setAction("取消", v -> {

                            imActiveChatList.add(pos, imActiveChat);
                            chatRVAdapter.notifyItemInserted(pos);
                            isDelete = false;

                        }).setCallback(new Snackbar.Callback() {
                    @Override
                    public void onDismissed(Snackbar snackbar, int event) {
                        super.onDismissed(snackbar, event);
                        if (isDelete) {
                            StorageImActiveChat.getInstance((Application) UiUtils.getContext()).deleteAChatRoom(imActiveChat);
                            //未读消息删除
                            Flowable.fromCallable(() -> StorageImMessage.getInstance(QNApplication.getContext()).findMessageById(imActiveChat.getUserId(), 100)).subscribeOn(Schedulers.io())
                                    .observeOn(AndroidSchedulers.mainThread())
                                    .subscribe(SingleChatListFragment.this::setMessageReaded);

                        }
                    }
                }).show();

            }

            //处理动画
            @Override
            public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
                if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
                    //滑动时改变 Item 的透明度，以实现滑动过程中实现渐变效果
                    final float alpha = 1 - Math.abs(dX) / (float) viewHolder.itemView.getWidth();
                    viewHolder.itemView.setAlpha(alpha);
                    viewHolder.itemView.setTranslationX(dX);
                } else {
                    super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
                }
            }
            //滑动事件完成时回调
            //在这里可以实现撤销操作

            //是否长按进行拖拽
            @Override
            public boolean isLongPressDragEnabled() {
                return true;
            }
        });
        touchHelper.attachToRecyclerView(recycleview);

onMove在滑动结束的时候调用，而onSwip在滑动的时候调用。实现的逻辑需要自己编写，实现起来也不困难。