我正在尝试创建一个Fragment,其中包含一个公共方法,用于向其自身添加子Fragment。
我已经阅读了一些可能类似的问题,但目前还没有找到任何有助于解决问题的内容。我将问题简化为了下面展示的一个简单的测试应用程序。
一旦将fragA
添加到主布局中,我调用公共方法fragA.addFragB()
来使其向自身添加一个FragmentClassB的实例,但这会导致测试应用程序崩溃,提示“Activity has been destroyed”(请参见本文末尾的LogCat)。这是不是意味着fragA
已被销毁,因此我不能将fragB
添加到它上面,还是意味着fragB
已被销毁,因此我不能将其添加到fragA
上?还是说它意味着完全不同的事情?
MainActivity.java
public class MainActivity extends FragmentActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragmentManager fragMan = getSupportFragmentManager();
// add Fragment A to the main linear layout
FragmentTransaction fragTrans = fragMan.beginTransaction();
FragmentClassA fragA = new FragmentClassA();
fragTrans.add(R.id.mainLinearLayout, fragA);
fragTrans.addToBackStack("A");
fragTrans.commit();
// get Fragment A to add a Fragment B to itself
fragA.addFragB();
}
}
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<LinearLayout
android:id="@+id/mainLinearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:orientation="horizontal" >
</LinearLayout>
</RelativeLayout>
FragmentClassA.java
public class FragmentClassA extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
public void addFragB() {
FragmentManager childFragMan = getChildFragmentManager();
FragmentTransaction childFragTrans = childFragMan.beginTransaction();
FragmentClassB fragB = new FragmentClassB();
childFragTrans.add(R.id.fragA_LinearLayout, fragB);
childFragTrans.addToBackStack("B");
childFragTrans.commit();
}
}
fragment_a.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragA_LinearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
</LinearLayout>
FragmentClassB.java
public class FragmentClassB extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_b, container, false);
}
}
fragment_b.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
LogCat
11-18 16:17:05.627: E/AndroidRuntime(14351): FATAL EXCEPTION: main
11-18 16:17:05.627: E/AndroidRuntime(14351): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.nestedfragmenttest/com.example.nestedfragmenttest.MainActivity}: java.lang.IllegalStateException: Activity has been destroyed
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.os.Handler.dispatchMessage(Handler.java:99)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.os.Looper.loop(Looper.java:137)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-18 16:17:05.627: E/AndroidRuntime(14351): at java.lang.reflect.Method.invokeNative(Native Method)
11-18 16:17:05.627: E/AndroidRuntime(14351): at java.lang.reflect.Method.invoke(Method.java:525)
11-18 16:17:05.627: E/AndroidRuntime(14351): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-18 16:17:05.627: E/AndroidRuntime(14351): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-18 16:17:05.627: E/AndroidRuntime(14351): at dalvik.system.NativeStart.main(Native Method)
11-18 16:17:05.627: E/AndroidRuntime(14351): Caused by: java.lang.IllegalStateException: Activity has been destroyed
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1365)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:595)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:574)
11-18 16:17:05.627: E/AndroidRuntime(14351): at com.example.nestedfragmenttest.FragmentClassA.addFragB(FragmentClassA.java:26)
11-18 16:17:05.627: E/AndroidRuntime(14351): at com.example.nestedfragmenttest.MainActivity.onCreate(MainActivity.java:25)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.Activity.performCreate(Activity.java:5133)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-18 16:17:05.627: E/AndroidRuntime(14351): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
11-18 16:17:05.627: E/AndroidRuntime(14351): ... 11 more
编辑:
ianhanniballake的答案和后来扩展了同样观点的GrIsHu的回答都有助于指出问题的根源。但是这引发了另一个问题。
最终意图是FragmentClassA将成为一个库的一部分。它将在多种情况下使用,FragmentClassB实例的数量会变化,甚至可能没有。因此,我需要能够从父activity触发将子fragment添加到FragmentClassA的任何实例中。我刚刚看了一下,在MainActivity中保持fragA
作为类级别变量,然后在MainActivity
的onActivityCreated()
方法中调用fragA.AddFragB()
,但它无法被覆盖。有什么想法吗?
FragmentA
类将在哪个库中? - GrIsHu