屏幕旋转

支持Android DialogFragment崩溃，我想转我的应用程序使用对话片段，但旋转屏幕时，而对话是可见的，我得到一个应用程序崩溃。我可以在下面描述的一个非常简单的应用程序中复制这个。创建Android Studio中一个新的项目并添加DialogFragment像这样：屏幕旋转

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; 
     } 
    } 
}

现在运行的应用程序，并经过对话显示出来（加载后1秒），旋转屏幕。请注意，我只在上面的初始onCreate上创建对话框。

这里是例外即时得到：

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这个脚本是这样的：

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:+' 
}

当你创建一个新的项目，这就是标准的构建脚本，并使用了最新的Android支持jar。

我可以在DialogFragment的onCreate方法做setRetainInstance，然后它不会崩溃，但该对话框被驳回旋转。这显然比崩溃更好，但不是我正在寻找的东西。

我真的不知道用什么样的DialogFragments首选的方法是，但我从直接从谷歌一些示例代码（用于谷歌的服务SDK）这个想法。我想他们知道他们在做什么，所以我会用同样的概念。

来源

2014-01-30 Matt Wolfe

当第一次创建活动中，savedInstanceState为null，因为它必须保存没有以前的状态。当屏幕旋转时，活动被破坏，并且onCreate(savedInstanceState)被再次调用并保存了一些状态（例如您的DialogFragment状态，这是可见的）。

所以，首先你savedInstaceState为空，当屏幕旋转时，实例的保存，然后在onCreate(savedInstanceState)恢复，所以它不是空了和任何内部if(savedInstanceState == null)将被调用，然后你得到了NullPointerException。

要解决此问题，删除此验证：

if(savedInstanceState == null){ 

    ///blablalba 

}

来源

2014-01-30 21:24:58

没有。我想到了这一点，其实我还没有提交答案。我必须在DialogFragment的onCreateDialog中创建对话框。我传递给对话的实例似乎会导致问题。不确定究竟为什么。 –

@MattWolfe你应该使用MyDialogFragment类中的以前的对话状态，而不是Activity类，你试过了吗？ –

我不想回答我的问题，但我想通了崩溃的原因。我需要实际上在DialogFragment的onCreateDialog中创建对话框，而不是从我的Activity中进行设置。不完全确定为什么这种情况。也许轮换时，android系统会删除与活动旧实例相关的引用。这并非完全理想，但我可以或许用来创建对话框中的数据传递

这里使用它的更新代码上旋转工作没有崩溃：

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(); 
     } 
    } 
}

来源

2014-01-30 22:13:05

我解决了这样的通过子类DialogFragment类和压倒一切的接下来的两个生命周期回调方法的一个问题：这不是它在所有..我不希望显示一个新的对话框我想恢复以前的一个

@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(); 
}

来源

2015-08-13 23:26:45 Andrey

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