绝密android初学者在fragment中常放的错误和对应的解决办法-福州大学城社区

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

/ 福州大学Android工程师 / 2017-05-05

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：

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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：

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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：

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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. }