旋转丢失片段

Question

我在我的应用程序中遇到问题，即使使用了一些最基本的代码（请参见下文），我在循环中丢失片段视图。

一切都开始了伟大的：

直到你旋转：

故事是相同的其他方式还有：

我不确定发生了什么事。我试图遵循各种教程和代码示例，通过日志记录进行检查以确保碎片正在保存和恢复，但无济于事。我究竟做错了什么？

MainActivity.java

public class MainActivity extends FragmentActivity 
{ 
    private FragmentManager fragment_manager; 
    private CharacterMenuFragment characterMenuFragment; 
    private CharacterEditFragment characterEditFragment; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.content_frame); 

     fragment_manager = getSupportFragmentManager(); 

     if (savedInstanceState != null) { 
      characterMenuFragment = (CharacterMenuFragment) fragment_manager.getFragment(savedInstanceState, "characterMenuFragment"); 
      characterEditFragment = (CharacterEditFragment) fragment_manager.getFragment(savedInstanceState, "characterEditFragment"); 
     } 

     if (characterMenuFragment == null) { 
      Log.i("characterMenuFragment", "making new fragment"); 
      characterMenuFragment = new CharacterMenuFragment(); 
     } else { 
      Log.i("characterMenuFragment", "re-using old fragment"); 
     } 

     if (characterEditFragment == null) { 
      Log.i("characterEditFragment", "making new fragment"); 
      characterEditFragment = new CharacterEditFragment(); 
     } else { 
      Log.i("characterEditFragment", "re-using old fragment"); 
     } 

     fragment_manager.beginTransaction().replace(R.id.menu_frame, characterMenuFragment).commit(); 
     fragment_manager.beginTransaction().replace(R.id.content_frame, characterEditFragment).commit(); 
    } 

    @Override 
    public void onSaveInstanceState(Bundle savedInstanceState) { 
     super.onSaveInstanceState(savedInstanceState); 

     fragment_manager.putFragment(savedInstanceState, "characterMenuFragment", characterMenuFragment); 
     fragment_manager.putFragment(savedInstanceState, "characterEditFragment", characterEditFragment); 
    } 
} 

CharacterEditFragment.java

public class CharacterEditFragment extends Fragment { 

    private View view; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     view = inflater.inflate(R.layout.hello_world, container, false); 
     return view; 
    } 

} 

CharacterMenuFragment.java

public class CharacterMenuFragment extends Fragment { 

    private View view; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     view = inflater.inflate(R.layout.hello_world, container, false); 
     return view; 
    } 

} 

content_frame.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" > 

    <FrameLayout 
     android:id="@+id/menu_frame" 
     android:layout_width="0dp" 
     android:layout_height="match_parent" 
     android:layout_weight="1" /> 

    <FrameLayout 
     android:id="@+id/content_frame" 
     android:layout_width="0dp" 
     android:layout_height="match_parent" 
     android:layout_weight="2" /> 

</LinearLayout> 

hello_world.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="vertical" > 

    <TextView 
     android:id="@+id/textView1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/hello_world" /> 

</LinearLayout> 

Answer 1

试试这个：

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.content_frame); 

    fragment_manager = getSupportFragmentManager(); 

    if (savedInstanceState != null) { 
     characterMenuFragment = (CharacterMenuFragment) fragment_manager.getFragment(savedInstanceState, "characterMenuFragment"); 
     characterEditFragment = (CharacterEditFragment) fragment_manager.getFragment(savedInstanceState, "characterEditFragment"); 
    } 

    if (characterMenuFragment == null) { 
     Log.i("characterMenuFragment", "making new fragment"); 
     characterMenuFragment = new CharacterMenuFragment(); 
     fragment_manager.beginTransaction().replace(R.id.menu_frame, characterMenuFragment).commit(); 
    } else { 
     Log.i("characterMenuFragment", "re-using old fragment"); 
    } 

    if (characterEditFragment == null) { 
     Log.i("characterEditFragment", "making new fragment"); 
     characterEditFragment = new CharacterEditFragment(); 
     fragment_manager.beginTransaction().replace(R.id.content_frame, characterEditFragment).commit(); 
    } else { 
     Log.i("characterEditFragment", "re-using old fragment"); 
    } 
} 

移动片段经理到适用，如果上述声明。您只需确保重用现有片段，并且仅在片段不存在时才创建一个片段。