调用的ViewGroup＃addView和一个ViewGroup＃removeView导致NullPointerException异常

问题描述：

里面的方法，我称之为addView和removeView如下：调用的ViewGroup＃addView和一个ViewGroup＃removeView导致NullPointerException异常

public class EnclosingClass extends FrameLayout { 
    ... 
    void fooMethod() { 
     ... 
     viewGroup1.addView(this); 
     viewGroup2.removeView(this); 
     ... 
    } 
    ... 
}

这部作品肖像模式罚款（它被称为很多次都没有任何问题），但当我改变屏幕为横向的方向，我得到了NullPointerException：（仅供参考，fooMethod正在从surfaceChanged方向变化时的称呼）：

18376   AndroidRuntime E FATAL EXCEPTION: main 
18376   AndroidRuntime E Process: com.google.android.apps.chrome, PID: 18376 
18376   AndroidRuntime E java.lang.NullPointerException 
18376   AndroidRuntime E at android.widget.FrameLayout.layoutChildren(FrameLayout.java:405) 
18376   AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 
18376   AndroidRuntime E at android.view.View.layout(View.java:14817) 
18376   AndroidRuntime E at android.view.ViewGroup.layout(ViewGroup.java:4631) 
18376   AndroidRuntime E at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 
18376   AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 
18376   AndroidRuntime E at android.view.View.layout(View.java:14817) 
18376   AndroidRuntime E at android.view.ViewGroup.layout(ViewGroup.java:4631) 
18376   AndroidRuntime E at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 
18376   AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 
18376   AndroidRuntime E at android.view.View.layout(View.java:14817) 
18376   AndroidRuntime E at android.view.ViewGroup.layout(ViewGroup.java:4631) 
18376   AndroidRuntime E at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1987) 
18376   AndroidRuntime E at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1744) 
18376   AndroidRuntime E at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000) 
18376   AndroidRuntime E at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670) 
18376   AndroidRuntime E at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) 
18376   AndroidRuntime E at android.view.Choreographer.doCallbacks(Choreographer.java:574) 
18376   AndroidRuntime E at android.view.Choreographer.doFrame(Choreographer.java:544) 
18376   AndroidRuntime E at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) 
18376   AndroidRuntime E at android.os.Handler.handleCallback(Handler.java:733) 
18376   AndroidRuntime E at android.os.Handler.dispatchMessage(Handler.java:95) 
18376   AndroidRuntime E at android.os.Looper.loop(Looper.java:136) 
18376   AndroidRuntime E at android.app.ActivityThread.main(ActivityThread.java:5017) 
18376   AndroidRuntime E at java.lang.reflect.Method.invokeNative(Native Method) 
18376   AndroidRuntime E at java.lang.reflect.Method.invoke(Method.java:515) 
18376   AndroidRuntime E at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
18376   AndroidRuntime E at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
18376   AndroidRuntime E at dalvik.system.NativeStart.main(Native Method)

在或DER来解决这个问题，我把addView和removeView一个Runnable里面如下：

void fooMethod() { 
    ... 
    new Handler().post(new Runnable() { 
     @Override 
     public void run() { 
      viewGroup1.addView(EnclosingClass.this); 
      viewGroup2.removeView(EnclosingClass.this); 
    }); 
    ... 
}

这并不能解决问题，而且似乎一切都工作正常，但我不明白为什么。如何将消息队列中的方法解决问题？另外，为什么我在栈跟踪中看不到任何对我的代码的引用？我通过逐渐注释掉代码来发现问题。

答

public final void runOnUiThread(Runnable action) { 
    if (Thread.currentThread() != mUiThread) { 
     mHandler.post(action); 
    } else { 
     action.run(); 
    }`enter code here` 
}

监守您使用runOnUiThread上真的UIThread，等等else分支代码的运行：）action.run（这是其他。如果API一个串行操作仍与当地mChildCount UI线程中运行时，会遇到NULL指针，（UI线程不安全）

调用的ViewGroup＃addView和一个ViewGroup＃removeView导致NullPointerException异常

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