屏幕旋轉

支持Android DialogFragment崩潰，我想轉我的應用程序使用對話片段，但旋轉屏幕時，而對話是可見的，我得到一個應用程序崩潰。我可以在下面描述的一個非常簡單的應用程序中複製這個。創建Android Studio中一個新的項目並添加DialogFragment像這樣：屏幕旋轉

public class MainActivity extends ActionBarActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     if (savedInstanceState == null) { 
      getSupportFragmentManager().beginTransaction() 
        .add(R.id.container, new PlaceholderFragment()) 
        .commit(); 
     } 
     if (savedInstanceState == null) { 
      (new Handler()).postDelayed(new Runnable() { 
       @Override 
       public void run() { 
        AlertDialog dialog = new AlertDialog.Builder(MainActivity.this) 
          .setMessage("Alert") 
          .setTitle("My Alert") 
          .create(); 
        MyDialogFragment dialogFragment = new MyDialogFragment(); 
        dialogFragment.setDialog(dialog); 
        dialogFragment.show(getSupportFragmentManager(), "dialog"); 

       } 
      }, 1000); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 
     if (id == R.id.action_settings) { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    /** 
    * A placeholder fragment containing a simple view. 
    */ 
    public static class PlaceholderFragment extends Fragment { 

     public PlaceholderFragment() { 
     } 

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

     @Override 
     public void onActivityCreated(Bundle savedState) { 
      super.onActivityCreated(savedState); 
     } 
    } 

    public static class MyDialogFragment extends DialogFragment { 
     private Dialog mDialog; 

     public MyDialogFragment() { 
      super(); 
      mDialog = null; 
     } 

     @Override 
     public void onCreate(Bundle state) { 
      super.onCreate(state); 
     } 

     // Set the dialog to display 
     public void setDialog(Dialog dialog) { 
      mDialog = dialog; 
     } 

     // Return a Dialog to the DialogFragment. 
     @Override 
     public Dialog onCreateDialog(Bundle savedInstanceState) { 
      return mDialog; 
     } 
    } 
}

現在運行的應用程序，並經過對話顯示出來（加載後1秒），旋轉屏幕。請注意，我只在上面的初始onCreate上創建對話框。

這裏是例外即時得到：

01-30 11:19:40.199 31986-31986/? E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.example.testdialogs, PID: 31986 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.testdialogs/com.example.testdialogs.MainActivity}: java.lang.NullPointerException 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265) 
      at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3758) 
      at android.app.ActivityThread.access$900(ActivityThread.java:145) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1212) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:136) 
      at android.app.ActivityThread.main(ActivityThread.java:5081) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at android.support.v4.app.DialogFragment.onActivityCreated(DialogFragment.java:368) 
      at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1508) 
      at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947) 
      at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104) 
      at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1086) 
      at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1884) 
      at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:566) 
      at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171) 
      at android.app.Activity.performStart(Activity.java:5241) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265) 
            at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3758) 
            at android.app.ActivityThread.access$900(ActivityThread.java:145) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1212) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:136) 
            at android.app.ActivityThread.main(ActivityThread.java:5081) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
            at dalvik.system.NativeStart.main(Native Method)

我gradle這個腳本是這樣的：

apply plugin: 'android' 

android { 
    compileSdkVersion 19 
    buildToolsVersion "19.0.1" 

    defaultConfig { 
     minSdkVersion 9 
     targetSdkVersion 19 
     versionCode 1 
     versionName "1.0" 
    } 

    compileOptions { 
     sourceCompatibility JavaVersion.VERSION_1_7 
     targetCompatibility JavaVersion.VERSION_1_7 
    } 
    buildTypes { 
     release { 
      runProguard false 
      proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt' 
     } 
    } 
} 

dependencies { 
    compile 'com.android.support:appcompat-v7:+' 
}

當你創建一個新的項目，這就是標準的構建腳本，並使用了最新的Android支持jar。

我可以在DialogFragment的onCreate方法做setRetainInstance，然後它不會崩潰，但該對話框被駁回旋轉。這顯然比崩潰更好，但不是我正在尋找的東西。

我真的不知道用什麼樣的DialogFragments首選的方法是，但我從直接從谷歌一些示例代碼（用於谷歌的服務SDK）這個想法。我想他們知道他們在做什麼，所以我會用同樣的概念。

來源

2014-01-30 Matt Wolfe

當第一次創建活動中，savedInstanceState爲null，因爲它必須保存沒有以前的狀態。當屏幕旋轉時，活動被破壞，並且onCreate(savedInstanceState)被再次調用並保存了一些狀態（例如您的DialogFragment狀態，這是可見的）。

所以，首先你savedInstaceState爲空，當屏幕旋轉時，實例的保存，然後在onCreate(savedInstanceState)恢復，所以它不是空了和任何內部if(savedInstanceState == null)將被調用，然後你得到了NullPointerException。

要解決此問題，刪除此驗證：

if(savedInstanceState == null){ 

    ///blablalba 

}

來源

2014-01-30 21:24:58

沒有。我想到了這一點，其實我還沒有提交答案。我必須在DialogFragment的onCreateDialog中創建對話框。我傳遞給對話的實例似乎會導致問題。不確定究竟爲什麼。 –

@MattWolfe你應該使用MyDialogFragment類中的以前的對話狀態，而不是Activity類，你試過了嗎？ –

我不想回答我的問題，但我想通了崩潰的原因。我需要實際上在DialogFragment的onCreateDialog中創建對話框，而不是從我的Activity中進行設置。不完全確定爲什麼這種情況。也許輪換時，android系統會刪除與活動舊實例相關的引用。這並非完全理想，但我可以或許用來創建對話框中的數據傳遞

這裏使用它的更新代碼上旋轉工作沒有崩潰：

public class MainActivity extends ActionBarActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     if (savedInstanceState == null) { 
      getSupportFragmentManager().beginTransaction() 
        .add(R.id.container, new PlaceholderFragment()) 
        .commit(); 
     } 
     if (savedInstanceState == null) { 
      (new Handler()).postDelayed(new Runnable() { 
       @Override 
       public void run() { 
        MyDialogFragment dialogFragment = new MyDialogFragment(); 
        dialogFragment.show(getSupportFragmentManager(), "dialog"); 

       } 
      }, 1000); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 
     if (id == R.id.action_settings) { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    /** 
    * A placeholder fragment containing a simple view. 
    */ 
    public static class PlaceholderFragment extends Fragment { 

     public PlaceholderFragment() { 
     } 

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

     @Override 
     public void onActivityCreated(Bundle savedState) { 
      super.onActivityCreated(savedState); 
     } 
    } 

    public static class MyDialogFragment extends DialogFragment { 
     public MyDialogFragment() { 
      super(); 
     } 

     @Override 
     public void onCreate(Bundle state) { 
      super.onCreate(state); 
     } 


     // Return a Dialog to the DialogFragment. 
     @Override 
     public Dialog onCreateDialog(Bundle savedInstanceState) { 
      return AlertDialog dialog = new AlertDialog.Builder(MainActivity.this) 
         .setMessage("Alert") 
         .setTitle("My Alert") 
         .create(); 
     } 
    } 
}

來源

2014-01-30 22:13:05

我解決了這樣的通過子類DialogFragment類和壓倒一切的接下來的兩個生命週期回調方法的一個問題：這不是它在所有..我不希望顯示一個新的對話框我想恢復以前的一個

@Override 
public void onCreate(@Nullable Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setRetainInstance(true); 
} 

@Override 
public void onDestroyView() { 
    if (getDialog() != null && getRetainInstance()) { 
     getDialog().setDismissMessage(null); 
    } 
    super.onDestroyView(); 
}

來源

2015-08-13 23:26:45 Andrey

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