ListView数据源不同步问题The content of the adapter has changed but ListView did not receive a notification.

最近项目中出现了很多下面的异常：

java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(16908298, class com.handmark.pulltorefresh.library.PullToRefreshListView$InternalListViewSDK9) with Adapter(class android.widget.HeaderViewListAdapter)]at android.widget.ListView.layoutChildren(ListView.java:1538)at android.widget.ListView.setSelectionInt(ListView.java:1955)at android.widget.AbsListView.resurrectSelection(AbsListView.java:5269)at android.widget.AbsListView.onWindowFocusChanged(AbsListView.java:2792)at android.view.View.dispatchWindowFocusChanged(View.java:7325)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:933)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewGroup.dispatchWindowFocusChanged(ViewGroup.java:937)at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2890)at android.os.Handler.dispatchMessage(Handler.java:99)at android.os.Looper.loop(Looper.java:137)at android.app.ActivityThread.main(ActivityThread.java:4745)at java.lang.reflect.Method.invokeNative(Native Method)at java.lang.reflect.Method.invoke(Method.java:511)at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)at dalvik.system.NativeStart.main(Native Method)

追踪该异常，发现其源头都来自于ListView.layoutChildren()方法

ListView比较了mItemCount和Adapter的getCount，发现两者不相等，抛出异常

这个mItemCount就是ListView内部缓存的一个子条目的个数，adapter的getCount就是我们继承Adapter重写的方法，返回数据源的个数

所以我们就知道：

当listView的layout.layoutChildren()方法被调用时，其内部缓存的条目个数和我们的数据源数量不一致时，会抛出此异常

通俗点就是，数据源变化没有及时通知到ListView

接下来看下代码：

list.addAll(data);

hideWaiting();

adapter.setData(list);

adapter.notifyDataSetChanged();

很简单的代码，改变数据源，然后setData，然后notifyDataSetChanged

表面看起来没有任何问题，但是请注意，第二行数据源修改后调用了hideWaiting方法，隐藏Dialog

这个操作就有可能触发系统重绘界面，一直调用到layouChildren()，出现问题，抛出异常

那么layoutChildren()的调用时机呢？

当界面发生任何改变时，如创建销毁，输入法弹出隐藏，显示隐藏Dialog，都会调用到该方法

此方法是由系统调用的，充满了不确定性，所以尽量还是及时通知更新数据

总结：

使用Adapter一定要注意，修改数据源后及时通知更新，否则一旦系统因为某种原因重绘界面，就会出现问题