RecyclerView解析--onViewDetachedFromWindow()/onViewAttachedToWindow()

先看這段源碼介紹：

/**
         * 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.
（當適配器創建的view（即列表項view）被窗口分離（即滑動離開了當前窗口界面）就會被調用）

 

這個方法就是用來當你的列表項滑出可見窗口之外的時候，需要重寫此方法進行相應的一些操作。

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這個方法具體什么時候用呢？

比如：

我有一個列表，列表的每一個列表項里面都要播放一個短視頻，這時候，當我滑動一個列表項直至它消失在可視界面時，便會調用onViewDetachedFromWindow()方法，重要的一點，視頻控件也會執行它自己的onViewDetachedFromWindow()方法，那么此時我再滑動回來，讓該列表項出現在當前界面，會發現視頻那一部分就是黑屏或者白屏了。

注意，出現這個Bug的條件是，該列表項滑動出可視界面，但是滑動距離不長，因為長的話，你再滑回來就會復用View執行onBindViewHolder()方法。

解決方法就是在RecyclerView中重寫onViewDetachedFromWindow()方法，對視頻進行一個相應的操作（初始化等等）。

 

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 對應方法：onViewAttachedToWindow() 

 當列表項出現到可視界面的時候調用

/**
         * 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) {
        }