绝密android初学者在fragment中常放的错误和对应的解决办法Android工程师
android初学者在fragment中常放的错误和对应的解决办法
第一个、使用ListFragment：java.lang.RuntimeException:
Content has view with id attribute 'android.R.id.list' that is not a ListView class在ListFragment中，想当然的以为，像其他Fragment一样：
[java] view plain copy
01.public class ListFragmentTest extends ListFragment {
03. @Override
04. public View onCreateView(LayoutInflater inflater, ViewGroup container,
05. Bundle savedInstanceState) {
06. View root = inflater.inflate(R.layout.list, null);
07. return root;
08. }
在list.xml里面：
[html] view plain copy
01.<?xml version="1.0" encoding="utf-8"?>
02.<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
03. android:layout_width="fill_parent"
04. android:layout_height="fill_parent"
05. android:orientation="vertical" >
07. <TextView
08. android:layout_width="wrap_content"
09. android:layout_height="wrap_content"
10. android:text="@string/app_name"
11. />
12. <ListView
13. android:id="@+id/list"
14. android:layout_width="fill_parent"
15. android:layout_height="fill_parent"
16. ></ListView>
17.</LinearLayout>
看下log：
[java] view plain copy
01.07-16 15:43:22.026: E/AndroidRuntime(605): FATAL EXCEPTION: main
02.07-16 15:43:22.026: E/AndroidRuntime(605): java.lang.RuntimeException: Unable to start activity ComponentInfo{cn.demo/cn.demo.FragmentTestActivity}: android.view.InflateException: Binary XML file line #23: Error inflating class fragment
03.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
04.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
05.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ActivityThread.access$600(ActivityThread.java:123)
06.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
07.07-16 15:43:22.026: E/AndroidRuntime(605): at android.os.Handler.dispatchMessage(Handler.java:99)
08.07-16 15:43:22.026: E/AndroidRuntime(605): at android.os.Looper.loop(Looper.java:137)
09.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ActivityThread.main(ActivityThread.java:4424)
10.07-16 15:43:22.026: E/AndroidRuntime(605): at java.lang.reflect.Method.invokeNative(Native Method)
11.07-16 15:43:22.026: E/AndroidRuntime(605): at java.lang.reflect.Method.invoke(Method.java:511)
12.07-16 15:43:22.026: E/AndroidRuntime(605): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
13.07-16 15:43:22.026: E/AndroidRuntime(605): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
14.07-16 15:43:22.026: E/AndroidRuntime(605): at dalvik.system.NativeStart.main(Native Method)
15.07-16 15:43:22.026: E/AndroidRuntime(605): Caused by: android.view.InflateException: Binary XML file line #23: Error inflating class fragment
16.07-16 15:43:22.026: E/AndroidRuntime(605): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:697)
17.07-16 15:43:22.026: E/AndroidRuntime(605): at android.view.LayoutInflater.rInflate(LayoutInflater.java:739)
18.07-16 15:43:22.026: E/AndroidRuntime(605): at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
19.07-16 15:43:22.026: E/AndroidRuntime(605): at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
20.07-16 15:43:22.026: E/AndroidRuntime(605): at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
21.07-16 15:43:22.026: E/AndroidRuntime(605): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:251)
22.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.Activity.setContentView(Activity.java:1835)
23.07-16 15:43:22.026: E/AndroidRuntime(605): at cn.demo.FragmentTestActivity.onCreate(FragmentTestActivity.java:11)
24.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.Activity.performCreate(Activity.java:4465)
25.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
26.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
27.07-16 15:43:22.026: E/AndroidRuntime(605): ... 11 more
28.07-16 15:43:22.026: E/AndroidRuntime(605): Caused by: java.lang.RuntimeException: Content has view with id attribute 'android.R.id.list' that is not a ListView class
29.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ListFragment.ensureList(ListFragment.java:402)
30.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.ListFragment.onViewCreated(ListFragment.java:203)
31.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:811)
32.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1010)
33.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1108)
34.07-16 15:43:22.026: E/AndroidRuntime(605): at android.app.Activity.onCreateView(Activity.java:4243)
35.07-16 15:43:22.026: E/AndroidRuntime(605): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:673)
36.07-16 15:43:22.026: E/AndroidRuntime(605): ... 21 more
为什么呢？因为ListFragment里面已经提供了系统自带的ListView，这样写，当然出错。可以直接不重写OnCreatView方法，使用getListView()获取系统提供的ListView.
但是获取的ListView设置Item间隔线只能getListView().setDivider(divider)，其参数为Drawable类型。当然如果只想简单的设置下Divider的颜色呢？
其实ListFragment当然运行自定义布局，但是Listview要用系统的：
[java] view plain copy
01.<?xml version="1.0" encoding="utf-8"?>
02.<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
03. android:layout_width="fill_parent"
04. android:layout_height="fill_parent"
05. android:orientation="vertical" >
07. <TextView
08. android:layout_width="wrap_content"
09. android:layout_height="wrap_content"
10. android:text="@string/app_name"
11. />
12. <ListView
13. android:id="@id/android:list"
14. android:layout_width="fill_parent"
15. android:layout_height="fill_parent"
16. ></ListView>
17.</LinearLayout>
第二个错误：FragmentManagerImpl.saveFragmentBasicState
下面是log：
[java] view plain copy
01.E/AndroidRuntime(29923): FATAL EXCEPTION: main
02.E/AndroidRuntime(29923): java.lang.NullPointerException
03.E/AndroidRuntime(29923): at android.app.FragmentManagerImpl.saveFragmentBasicState(FragmentManager.java:1544)
04.E/AndroidRuntime(29923): at android.app.FragmentManagerImpl.saveAllState(FragmentManager.java:1574)
05.E/AndroidRuntime(29923): at android.app.Activity.onSaveInstanceState(Activity.java:1213)
06.E/AndroidRuntime(29923): at android.app.Activity.performSaveInstanceState(Activity.java:1162)
07.E/AndroidRuntime(29923): at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1287)
08.E/AndroidRuntime(29923): at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:3208)
09.E/AndroidRuntime(29923): at android.app.ActivityThread.handleStopActivity(ActivityThread.java:3266)
10.E/AndroidRuntime(29923): at android.app.ActivityThread.access$900(ActivityThread.java:139)
11.E/AndroidRuntime(29923): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1279)
12.E/AndroidRuntime(29923): at android.os.Handler.dispatchMessage(Handler.java:99)
13.E/AndroidRuntime(29923): at android.os.Looper.loop(Looper.java:156)
14.E/AndroidRuntime(29923): at android.app.ActivityThread.main(ActivityThread.java:5005)
15.E/AndroidRuntime(29923): at java.lang.reflect.Method.invokeNative(Native Method)
16.E/AndroidRuntime(29923): at java.lang.reflect.Method.invoke(Method.java:511)
17.E/AndroidRuntime(29923): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
18.E/AndroidRuntime(29923): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
19.E/AndroidRuntime(29923): at dalvik.system.NativeStart.main(Native Method)
看老半天log,没有琢磨明白，在网上找了下，说出现这个问题，主要是以下两个因素：
一是用了Android.support.v4包, 二是FragmentActivity.
本人正是在从Fragment跳转到另一个Activity时候报的错，据说是个官方Bug，已经有程序员把这个问题提交到官方了，https://android-review.googlesource.com/#/c/31261/。
下面看看他们提交的内容：
If a fragment's saved view state is null and the user visible hint is true then the `result` bundle will have never been initialized to a value resulting in a `NullPointerException`.
如果一个Fragment保存的视图状态为Null并且用户可见提示为true，那么'result' bundle(要保存的Bundle)会有一个微博初始化的值，然后导致空指针异常。
如何解决此问题呢？问题出在Save上，在有Fragment的Activity中重写onSaveInstanceState()方法，并且注释掉super.onSaveInstanceState（），这样就不会调用父类的onSaveInstanceState(outState)方法了，就不会报异常了。
[java] view plain copy
01.outState 对象为空..在onSaveInstanceState()函数中不使用到outState即可.
02.
03.[java] view plaincopy
04.@Override
05. protected void onSaveInstanceState(Bundle outState) {
06. // TODO Auto-generated method stub
07. //super.onSaveInstanceState(outState);
08.
09. }
在这里，就可以方便的设置listview的各个参数了。
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