【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
posted @ 2014-07-28 21:51 陌上幽人 阅读(...) 评论(...) 编辑 收藏