在已创建父片段视图后添加嵌套片段

Question

我正在尝试创建一个Fragment,它有一个公共方法,可以将子Fragment添加到自身.

我一直在阅读可能类似的问题,但到目前为止还没有找到任何帮助.我已将问题简化为如下所示的简单测试应用程序.

一旦fragA添加到主布局,我调用public方法fragA.addFragB()让它为自己添加FragmentClassB的实例,但这会导致测试应用程序崩溃,表明"Activity已被销毁"(请参阅​​LogCat结尾处后).这是否意味着fragA已经被破坏所以我无法添加fragB它,或者它是否意味着fragB已经被破坏所以我不能添加它fragA？或者它完全意味着什么呢？

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中

<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的

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GrIsHu后来的答案扩展到了同一点,这些都有助于指出问题的根源.然而,这提出了另一个问题.
最后的意图是FragmentClassA将成为库的一部分.它将在多种情况下使用,FragmentClassB实例的数量会有所不同,甚至可能没有.因此,我需要能够从父活动触发将子片段添加到FragmentClassA的任何实例.我刚刚看了一下保持fragA在一个类级别的变量MainActivity,然后调用fragA.AddFragB()中MainActivity的onActivityCreated()方法,但它是不可被覆盖.有什么想法吗？

Answer 1

您无法直接加载已声明的片段FragA.首先加载FragmentA,然后通过调用方法addFragB()中的fragA's onCreateView()方法加载FragmentB .

试试如下:

fragA.addFragB();从MainActivity中删除该行

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();

    }

}

并尝试FragmentB从FragmentA下面加载from :

public class FragmentClassA extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        addFragB(); //Call and load fragment B here.
        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();

    }
}