(Child)FragmentManager正确使用子片段 [英] Proper use of sub sub fragments with (Child)FragmentManager

问题描述

如何在片段中正确使用片段?

How do I properly use Fragments in Fragments?

下面是我的(简化的)用例，我有一个带有布局片段的活动，该片段本身包含一个子片段...所有片段都手动添加到其父级中...

My (simplified) use case is following, I have an activity with a layout fragment and this fragment theirself contains a sub fragment... all fragments are added manually to their parents...

----------------------------------------------------------
- Activity                                               -
-                                                        -
-                                                        -
-     ---------------------------------------            -
-     - Fragment                            -            -
-     -                                     -            -
-     -    -----------------                -            -
-     -    - SubFragment   -                -            -
-     -    -               -                -            -
-     -    -               -                -            -
-     -    -----------------                -            -
-     ---------------------------------------            -
-                                                        -
----------------------------------------------------------

现在我在活动的onCreate中执行以下操作:

Now in my activity's onCreate I do following:

if (savedInstanceState == null)
{
    // I create the fragment
    mMainFragment = new MainFragment();
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.fragment_main, mMainFragment);
    transaction.commit();
}
else
{
    // I retrieve the fragment
    mMainFragment = (BaseFragment) getSupportFragmentManager().findFragmentById(R.id.fragment_main);
}

在片段onCreate中，我获取/创建了我的SubFragment:

And in my fragments onCreate I get/create my SubFragment:

mSubFragment = getChildFragmentManager().findFragmentByTag(SubFragment.class.getName());
if (mSubFragment == null)
{
    mSubFragment = new SubFragment();
    getChildFragmentManager().beginTransaction().add(R.id.fragment_sub, mSubFragment, SubFragment.class.getName()).commit();
}

问题

屏幕旋转后，我的SubFragment被添加了两次...如果我使用活动的FragmentManager，那么它可以工作...但是，为什么它不适用于ChildFragmentManager?当然，Fragment是一个新的片段，但活动也是一个新的片段，那么为什么它可以与活动的FragmentManager一起使用，而不与父片段的一起使用?

After screen rotation, my SubFragment is added twice... If I use the activity's FragmentManager then it works... But why does it not work with the ChildFragmentManager? Of course, the Fragment is a new fragment, but the activity is a new one as well, so why does it work with the activity's FragmentManager but not with the parent fragment's one?

在一个片段中，我应该使用片段ChildFragmentManager，不是吗?

In a fragment, I should use the fragments ChildFragmentManager, shouldn't I?

推荐答案

您应将SubFragment添加到Fragment，就像将Fragment添加到Activity一样.我的意思是将Fragment添加到Activity应该如下:

You should add SubFragment to Fragment the same way like you add Fragment to Activity. I mean adding Fragment to Activity should look like:

 @Override
 public void onCreate(Bundle savedInstanceState) {
   ....
   if (savedInstanceState == null){
      //add fragment
      mMainFragment = new MainFragment();
      FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
      transaction.replace(R.id.fragment_main, mMainFragment);
      transaction.commit();
   }
 }

将SubFragment添加到MainFragment应该如下所示:

Adding SubFragment to MainFragment should look like:

    public class MainFragment extends Fragment{

      @Override
      public View onCreateView(LayoutInflater i, ViewGroup c, Bundle savedInstanceState) {
           ...
        if (savedInstanceState == null){
           mSubFragment = new SubFragment();

           //add child fragment
           getChildFragmentManager()
                   .beginTransaction()
                   .add(R.id.fragment_sub, mSubFragment, "tag")
                   .commit();
        }
      }
    }

或您可以在onCreate方法

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