Question

我遇到了使用目标SDK 4.3编译并运行的Android应用程序的问题。该应用程序有两个活动，一个MainActivity，也是Launcher活动和SecondActivity。两者都在使用Fragments。为了支持旧设备，还使用了支持库。

在下面的场景中，它出现了“IllegalStateException：Fragment already added”错误。

1）启动应用程序 - ＆gt; MainActivity显示为 2）用Intent切换到SecondActivity 3）按主页按钮
4）等待更长时间（24小时测试）
5）再次按下应用程序图标 - ＆gt;例外。如果时间较短，则SecondActivity会像预期的那样显示。

我在Fragment处理过程中读过很多IllegalStateExceptions，但是所有这些都指向了replace（）方法的问题。在Stacktrace中，我自己的代码永远不会被调用。

Fragement添加在Activies onCreate（）方法：

中

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(..);
    ListFragment listFragment = this.getCaptureListFragment();
    FragmentTransaction tx = this.getSupportFragmentManager().beginTransaction();
    tx.add(R.id.MainFragmentContainer, listFragment, "list_fragment_tag");
    tx.commit(); 
}

private ListFragment getListFragment() {
    ListFragment listFragment = (ListFragment) this.getSupportFragmentManager().findFragmentByTag("list_fragment_tag");
    if (listFragment == null) {
        listFragment = new ListFragment();
    }
    return listFragment;
}


java.lang.RuntimeException: Unable to start activity    ComponentInfo{de.myexample.demo/de.myexample.demo.ui.SecondActivity}: java.lang.IllegalStateException: Fragment already added: ListFragment{42283f58 #0 id=0x7f060094 de.myexample.demo.ui.ListFragment}
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
    at android.app.ActivityThread.access$600(ActivityThread.java:141)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5103)
    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:737)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: Fragment already added: ListFragment{42283f58 #0 id=0x7f060094 de.myexample.demo.ui.ListFragment}
    at android.support.v4.app.FragmentManagerImpl.addFragment(SourceFile:1175)
    at android.support.v4.app.BackStackRecord.run(SourceFile:616)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(SourceFile:1460)
    at android.support.v4.app.FragmentActivity.onStart(SourceFile:556)
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
    at android.app.Activity.performStart(Activity.java:5143)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
    ... 11 more
java.lang.IllegalStateException: Fragment already added: ListFragment{42283f58 #0 id=0x7f060094 de.myexample.demo.ui.ListFragment}
    at android.support.v4.app.FragmentManagerImpl.addFragment(SourceFile:1175)
    at android.support.v4.app.BackStackRecord.run(SourceFile:616)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(SourceFile:1460)
    at android.support.v4.app.FragmentActivity.onStart(SourceFile:556)
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
    at android.app.Activity.performStart(Activity.java:5143)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
    at android.app.ActivityThread.access$600(ActivityThread.java:141)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5103)
    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:737)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    at dalvik.system.NativeStart.main(Native Method)

Answer 1

好的，我自己解决了。

我将所有片段放在onPause（）中并将状态存储在一些布尔值中。根据布尔值，片段放在onResume（）中。无论活动在后台运行多长时间，启动都是稳定的。

boolean addList = false;

@Override
protected void onResume() {
    FragmentTransaction tx = this.getSupportFragmentManager().beginTransaction();
    if (this.addList) {
        ListFragment list = this.getListFragment();
        tx.add(R.id.MainFragmentContainer, list, "list_fragment_tag");
    }

    tx.commit();
    super.onResume();

    this.addList = false;   

}

@Override
protected void onPause() {
    this.addList = this.getListFragment().isAdded();
    ...
    if (this.addList) {
        FragmentTransaction tx = this.getSupportFragmentManager().beginTransaction();
        tx.remove(this.getListFragment());
        tx.commit();
    }
    this.getSupportFragmentManager().executePendingTransactions();
    super.onPause();

}

也许这可以帮助有同样问题的人

Answer 2

为了重现这一点，人们可以激活“不要保持活动”。在设置 - ＆gt;开发者选项。然后暂停并恢复活动。

这样你就不必等待24小时了。）

Answer 3

片段管理器在退出时保存其状态。因此，您不必再次添加片段。

这样做：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(..);

    if (savedInstanceState == null) {
        ListFragment listFragment = this.getCaptureListFragment();
        FragmentTransaction tx = this.getSupportFragmentManager().beginTransaction();
        tx.add(R.id.MainFragmentContainer, listFragment, "list_fragment_tag");
        tx.commit(); 
    }
}

Answer 4

没有必要创建新的布尔字段来检查片段的添加状态。片段中还有一种方法。 只需使用它： myFragment.isAdded()

java.lang.IllegalStateException：已添加片段

4 个答案: