RecyclerView Adapter中notifyDataSetChanged 的作用

一直认为notifyDataSetChanged 是用来刷新数据的当数据发生变化的时候调用notifyDataSetChanged

官方说：通知任何注册的观察者数据发生了改变(Notify any registered observers that the data set has changed) --自己翻译的不保证完全正确。。。。。。

今天有空翻阅下源码

public final void notifyDataSetChanged() {mObservable.notifyChanged();
}

在看看 notifyChanged()方法

public void notifyChanged() {// since onChanged() is implemented by the app, it could do anything, including// removing itself from {@link mObservers} - and that could cause problems if// an iterator is used on the ArrayList {@link mObservers}.// to avoid such problems, just march thru the list in the reverse order.for (int i = mObservers.size() - 1; i >= 0; i--) {mObservers.get(i).onChanged();}
}

这里的mObservers 是一个list

protected final ArrayList<T> mObservers = new ArrayList<T>();

这样看来notifyDataSetChanged 是改变list 的元素

在看下源码的注释

相似的方法

* @see #notifyItemChanged(int)
* @see #notifyItemInserted(int)
* @see #notifyItemRemoved(int)
* @see #notifyItemRangeChanged(int, int)
* @see #notifyItemRangeInserted(int, int)
* @see #notifyItemRangeRemoved(int, int)

/*** Notify any registered observers that the data set has changed.** <p>There are two different classes of data change events, item changes and structural* changes. Item changes are when a single item has its data updated but no positional* changes have occurred. Structural changes are when items are inserted, removed or moved* within the data set.</p>** <p>This event does not specify what about the data set has changed, forcing* any observers to assume that all existing items and structure may no longer be valid.* LayoutManagers will be forced to fully rebind and relayout all visible views.</p>** <p><code>RecyclerView</code> will attempt to synthesize visible structural change events* for adapters that report that they have {@link #hasStableIds() stable IDs} when* this method is used. This can help for the purposes of animation and visual* object persistence but individual item views will still need to be rebound* and relaid out.</p>** <p>If you are writing an adapter it will always be more efficient to use the more* specific change events if you can. Rely on <code>notifyDataSetChanged()</code>* as a last resort.</p>

可以看到官方说 notifyDataSetChanged 的作用

Notify any registered observers that the data set has changed. 通知任何注册的观察者数据发生了改变

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