【原创】关于Adapter的The content of the adapter has changed问题分析

关于Adapter的The content of the adapter has changed问题分析

 

1、问题描述

 1 07-28 17:22:02.162: E/AndroidRuntime(16779): 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. Make sure your adapter calls notifyDataSetChanged() when its content changes. [in ListView(2131034604, class android.widget.ListView) with Adapter(class com.nodin.sarah.HeartListAdapter)]

 2 

 3 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.ListView.layoutChildren(ListView.java:1555)

 4 

 5 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.AbsListView.onLayout(AbsListView.java:2091)

 6 

 7 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

 8 

 9 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

10 

11 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)

12 

13 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

14 

15 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

16 

17 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)

18 

19 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.FrameLayout.onLayout(FrameLayout.java:388)

20 

21 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

22 

23 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

24 

25 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1589)

26 

27 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

28 

29 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

30 

31 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)

32 

33 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

34 

35 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

36 

37 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)

38 

39 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.FrameLayout.onLayout(FrameLayout.java:388)

40 

41 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

42 

43 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

44 

45 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)

46 

47 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)

48 

49 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)

50 

51 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

52 

53 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

54 

55 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)

56 

57 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.widget.FrameLayout.onLayout(FrameLayout.java:388)

58 

59 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.View.layout(View.java:14785)

60 

61 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewGroup.layout(ViewGroup.java:4631)

62 

63 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1985)

64 

65 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1742)

66 

67 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)

68 

69 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)

70 

71 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)

72 

73 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.Choreographer.doCallbacks(Choreographer.java:562)

74 

75 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.Choreographer.doFrame(Choreographer.java:532)

76 

77 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)

78 

79 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.os.Handler.handleCallback(Handler.java:733)

80 

81 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.os.Handler.dispatchMessage(Handler.java:95)

82 

83 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.os.Looper.loop(Looper.java:137)

84 

85 07-28 17:22:02.162: E/AndroidRuntime(16779):   at android.app.ActivityThread.main(ActivityThread.java:4998)

86 

87 07-28 17:22:02.162: E/AndroidRuntime(16779):   at java.lang.reflect.Method.invokeNative(Native Method)

88 

89 07-28 17:22:02.162: E/AndroidRuntime(16779):   at java.lang.reflect.Method.invoke(Method.java:515)

90 

91 07-28 17:22:02.162: E/AndroidRuntime(16779):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)

92 

93 07-28 17:22:02.162: E/AndroidRuntime(16779):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)

94 

95 07-28 17:22:02.162: E/AndroidRuntime(16779):   at dalvik.system.NativeStart.main(Native Method)

96 

97 07-28 17:22:02.162: W/ActivityManager(588):   Force finishing activity  

 

2、复现场景

使用ListView和Adapter实现动态增删数据列表功能，初始化数据分为两部分：本地和网络。所以在Adapter的数据初始化的时候，先讲本地数据添加到了容器内。同时发起网络请求，等加载完毕后追加到容器内。

问题出现在：当网络请求完毕后追加数据的时候，抛出上述异常。

 

3、原因分析

Exception解读：

         Adapter的数据内容已经改变，但是ListView却未接收到通知。要确保不在后台线程中修改Adapter的数据内容，而要在UI Thread中修改。确保Adapter的数据内容改变时一定要调用notifyDataSetChanged()方法。

 

且不管Exception内容，先查询Android源码看看该Exception是从哪里抛出来的。

在ListView的layoutChildren()方法里有如下一段方法：

 1 // Handle the empty set by removing all views that are visible

 2 // and calling it a day

 3 if (mItemCount == 0) {

 4     resetList();

 5     invokeOnItemScrollListener();

 6     return;

 7 } else if (mItemCount != mAdapter.getCount()) {

 8     throw new IllegalStateException("The content of the adapter has changed but "

 9             + "ListView did not receive a notification. Make sure the content of "

10             + "your adapter is not modified from a background thread, but only "

11             + "from the UI thread. [in ListView(" + getId() + ", " + getClass()

12             + ") with Adapter(" + mAdapter.getClass() + ")]");

13 }

 

亦即， 当ListView缓存的数据Count和ListView中Adapter.getCount()不等时，会抛出该异常。

 

结合开头的异常解读，可以断定肯定是Adapter数据动态更新的问题。仔细检查了自己的代码：

 

当网络请求完毕后，直接在网络线程（非UI线程）里调用了在Adapter中新增的自定义方法addData(List)更新数据，而addData(List)方法内更新换完数据后，通过Handler发送Message的策略调用Adapter的notifyDataSetChanged()方法通知更新。

 

这么一来，并不能保证Adapter的数据更新时，立马调用notifyDataSetChanged()通知ListView，这两个线程之间的时间差引起的数据不同步，导致ListView的layoutChildren()中访问Adapter的getCount()方法时，Adapter内已经是最新数据源，而ListView内的缓存数据Count仍是旧数据的Count，该问题最终原因终于浮出水面。

 

4、解决方案

在本例中，解决方案是： 把addData(List)方法内更新数据的代码挪出来，和notifyDataSetChanged()方法一同放在Handler里，保证数据更新时及时通知ListView。

 

为了尽量避免该问题，以后编程尽量从如下几个方面检查自己的代码：

• 确保Adapter的数据更新后一定要调用notifyDataSetChanged()方法通知ListView
• 数据更新和notifyDataSetChanged()放在UI线程内，且必须同步顺序执行，不可异步
• 仔细检查确认getCount()方法返回值是否正确