从容器中删除片段后,Fragment.isAdded返回true

Question

我有一个以下布局的活动

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

    <FrameLayout
        android:id="@+id/frameLayoutA"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_weight="1" >
    </FrameLayout>
    <FrameLayout
        android:id="@+id/frameLayoutB"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_weight="1" >
    </FrameLayout>
</LinearLayout>

在onCreate of activity中,我在frameLayoutA中加载Fragment_A,在frameLayoutB中加载Fragment_B.

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    fmA=(FrameLayout) findViewById(R.id.frameLayoutA);
    fmB=(FrameLayout) findViewById(R.id.frameLayoutB);

    fragA=new FragmentA();
    fragB=new FragmentB();
    fragC=new FragmentC();
    addFragmentsInActivity(R.id.frameLayoutA,fragA);
    addFragmentsInActivity(R.id.frameLayoutB,fragB);
}

public void addFragmentsInActivity(int id, Fragment fragment)
{
    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.add(id, fragment);
    fragmentTransaction.commit();
}

使用菜单操作我想在frameLayoutA中加载Fragment_B,在frameLayoutB中加载Fragment_C.菜单操作是:

    removeFragmentsInActivity(R.id.frameLayoutB,fragB);
    addFragmentsInActivity(R.id.frameLayoutB,fragC);
    if(!fragB.isAdded()){
            Log.e("check", "fragB already removed from frameLayoutB");
        removeFragmentsInActivity(R.id.frameLayoutB,fragB);
        addFragmentsInActivity(R.id.frameLayoutA,fragB);
    }
    else{
        Log.e("check", "fragB already added");
    }    

    public void removeFragmentsInActivity(int id, Fragment fragment)
    {
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.remove(fragment);
        fragmentTransaction.commit();
    }

Fragment_B未显示在frameLayoutA中.frameLayoutA显示Fragment_A.再次单击"菜单"操作时,将加载Fragment_B.

调试我发现,在fragB.remove()操作完成后,fragB.isAdded()返回true.在第二个菜单操作期间,fragB.isAdded()返回false并执行fragB.add()并在frameLayoutA中显示FragmentB.

我知道commit是一个异步操作.isAdded返回true,因为commit是异步的,并且直到调用fragB.isAdded()时才执行remove操作提交.这是真的吗？

请建议可能的解决方案或方法来解决问题.

此致,Vibhor

Answer 1

是的,事务是异步提交的.如果要在执行前确保所有trasactions都已完成isAdded,请运行:

getFragmentManager().executePendingTransactions();

从文档executePendingTransactions():

使用FragmentTransaction.commit()提交FragmentTransaction后,它将被安排在进程的主线程上异步执行.如果要立即执行任何此类挂起操作,可以调用此函数(仅从主线程)来执行此操作.请注意,所有回调和其他相关行为都将在此调用中完成,因此请注意调用它的位置.

所以你的代码应该是这样的:

removeFragmentsInActivity(R.id.frameLayoutB,fragB);
addFragmentsInActivity(R.id.frameLayoutB,fragC);
getFragmentManager().executePendingTransactions();
if(!fragB.isAdded()){
        Log.e("check", "fragB already removed from frameLayoutB");
    removeFragmentsInActivity(R.id.frameLayoutA,fragA);
    addFragmentsInActivity(R.id.frameLayoutA,fragB);
}
else{
    Log.e("check", "fragB already added");
}

注意还修复了片段A的删除.