Android IllegalArgumentException：如果应用在后台运行了一段时间，则状态类错误 [英] Android IllegalArgumentException: Wrong state class if the app was background for a period of time

问题描述

我认为这是由于我设置了应用背景导致的内存不足。
日志如下所示：

I think it is due to low memory if I set the app background. The log is like below:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.qingdaonews.bus/com.qingdaonews.activity.RealTime}: 
java.lang.IllegalArgumentException: Wrong state class, expecting View State but received class android.view.View$BaseSavedState instead. This usually happens when two views of different type have the same id in the same hierarchy. This view's id is id/myviewpager. Make sure other views do not use the same id.
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2266)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
    at android.app.ActivityThread.access$600(ActivityThread.java:150)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:213)
    at android.app.ActivityThread.main(ActivityThread.java:5225)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:525)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:741)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
    at dalvik.system.NativeStart.main(Native Method)

看起来由于相同的视图ID。实际上， id'myviewpager'仅ap一次出现在xml文件中，并且仅在从后台重新打开应用程序时才会出现问题。

It looks like due to the same id of a view.In fact ,the id 'myviewpager' only appear once in the xml file and the problem only occur when the app is reopen from background.

而且我的MainActivity有一个片段，可以我使用 getSupportFragmentManager（）。beginTransaction（）。replace（R.id.content_frame，fragment）.commit（）;
来替换它。活动。

没有'savedInstanceState'的超级方法，我没有使用其他东西。

And my MainActivity has one fragment which can be replaced in it.I use getSupportFragmentManager().beginTransaction().replace(R.id.content_frame, fragment).commit(); when I start the activity.
Without super method of 'savedInstanceState',I did not use something else.

推荐答案

原因是您的片段被重新添加。
您的代码如下：

The cause is that your Fragment gets re-added. Your code looks like this:

protected void onCreate(Bundle savedInstanceState){
    super(savedInstanceState);        
    ///...
    getSupportFragmentManager().beginTransaction()
        .replace(R.id.content_frame, fragment).commit();
}

如果 savedInstanceState！= null <，则恢复关联的FragmentManager / code>通过调用 super（savedInstanceState），所有提交的片段也将恢复。相反，请检查您的片段是否已添加，如果没有，则仅添加：

Associated FragmentManager gets restored if savedInstanceState != null via a call to super(savedInstanceState), and all the commited fragments get restored too. Instead, check if your fragment is already added, and add it only if not:

public class MyActivity extends Activity{

    private MyFragment myFragment;//extends Fragment

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //your stuff
        FragmentManager fm = getFragmentManager();
        myFragment = (MyFragment) fm.findFragmentByTag(MyFragment.TAG);
        if(myFragment == null){
            myFragment = new MyFragment();
            fm.beginTransaction()
                .add(R.id.content_frame, myFragment, MyFragment.TAG)
                .commit();
         }
        //other stuff
    }
}

在您的 MyFragment 中，TAG是：
public static final String TAG = MyFragment.class.getSimpleName（）;

And in your MyFragment, TAG is: public static final String TAG = MyFragment.class.getSimpleName();

对于我来说，我发现添加带有TAG参数的片段是一种不错的做法。

As for me, I found it is a nice practice to add Fragments with TAG parameter provided.

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