RecyclerView解析--onViewDetachedFromWindow()/onViewAttachedToWindow()

先看这段源码介绍：

/**
         * Called when a view created by this adapter has been detached from its window.
         *
         * <p>Becoming detached from the window is not necessarily a permanent condition;
         * the consumer of an Adapter's views may choose to cache views offscreen while they
         * are not visible, attaching an detaching them as appropriate.</p>
         *
         * @param holder Holder of the view being detached
         */
        public void onViewDetachedFromWindow(VH holder) {
        }

Called when a view created by this adapter has been detached from its window.
（当适配器创建的view（即列表项view）被窗口分离（即滑动离开了当前窗口界面）就会被调用）

这个方法就是用来当你的列表项滑出可见窗口之外的时候，需要重写此方法进行相应的一些操作。

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这个方法具体什么时候用呢？

比如：

我有一个列表，列表的每一个列表项里面都要播放一个短视频，这时候，当我滑动一个列表项直至它消失在可视界面时，便会调用onViewDetachedFromWindow()方法，重要的一点，视频控件也会执行它自己的onViewDetachedFromWindow()方法，那么此时我再滑动回来，让该列表项出现在当前界面，会发现视频那一部分就是黑屏或者白屏了。

注意，出现这个Bug的条件是，该列表项滑动出可视界面，但是滑动距离不长，因为长的话，你再滑回来就会复用View执行onBindViewHolder()方法。

解决方法就是在RecyclerView中重写onViewDetachedFromWindow()方法，对视频进行一个相应的操作（初始化等等）。

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 对应方法：onViewAttachedToWindow() 

 当列表项出现到可视界面的时候调用

/**
         * Called when a view created by this adapter has been attached to a window.
         *
         * <p>This can be used as a reasonable signal that the view is about to be seen
         * by the user. If the adapter previously freed any resources in
         * {@link #onViewDetachedFromWindow(RecyclerView.ViewHolder) onViewDetachedFromWindow}
         * those resources should be restored here.</p>
         *
         * @param holder Holder of the view being attached
         */
        public void onViewAttachedToWindow(VH holder) {
        }