的AsyncTask和Looper.prepare（）错误

Question

我有以下代码

class OverlayTask extends AsyncTask<Void, Void, Void> { 
    @Override 
    public void onPreExecute() { 

     if (sites != null) { 
      myMapView.getOverlays().remove(sites); 
      myMapView.invalidate(); 
      sites = null; 
     } 
    } 

    @Override 
    public Void doInBackground(Void... unused) { 
      grabShipsWithLocation(); 
      return (null); 
    } 

    @Override 
    public void onPostExecute(Void unused) { 
     myMapView.getOverlays().add(sites); 
     myMapView.invalidate(); 
     isLoading = false; 
    } 
} 

这似乎在一些测试设备工作正常，但我看到很多出现在开发者控制台上的错误。我似乎无法弄清楚为什么以及在哪里放置这个Looper.prepare（）。需要吗？

java.lang.ExceptionInInitializerError 
at com.test.appname.FinderMain$1.gotLocation(FinderMain.java:286) 
at com.test.appname.MyLocation$GetLastLocation.run(MyLocation.java:89) 
at java.util.Timer$TimerImpl.run(Timer.java:289) 
Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 
at android.os.Handler.<init>(Handler.java:121) 
at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421) 
at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421) 
at android.os.AsyncTask.<clinit>(AsyncTask.java:152) 

按照要求MyLocation.java

class GetLastLocation extends TimerTask { 
    @Override 
    public void run() { 
     lm.removeUpdates(locationListenerGps); 
     lm.removeUpdates(locationListenerNetwork); 

     Location net_loc=null, gps_loc=null; 
     if(gps_enabled) 
      gps_loc=lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); 
     if(network_enabled) 
      net_loc=lm.getLastKnownLocation(LocationManager.GPS_PROVIDER); 

     //if there are both values use the latest one 
     if(gps_loc!=null && net_loc!=null){ 
      if(gps_loc.getTime()>net_loc.getTime()) 
       locationResult.gotLocation(gps_loc); 
      else 
       locationResult.gotLocation(net_loc); 
      return; 
     } 

     if(gps_loc!=null){ 
      locationResult.gotLocation(gps_loc); //Line 89 
      return; 
     } 
     if(net_loc!=null){ 
      locationResult.gotLocation(net_loc); 
      return; 
     } 
     locationResult.gotLocation(null); 
    } 
} 

Answer 1

长的故事：

AsyncTask内部使用Handler。处理程序基本上可以让你从线程处理程序被分配到另一个线程，这在AsyncTask的情况下，总是从它被称为主题发表Runnables。但这只适用于准备Looper的线程。

欲了解更多信息，请参阅http://developer.android.com/reference/android/os/Handler.html

短篇小说：

简单包装每次调用FinderMain$1.gotLocation或在Runnable内它创造AsyncTask，并将其张贴到绑定到UI线程Handler ，像这样：

class GetLastLocation extends TimerTask { 
    private Handler mHandler = new Handler(Looper.getMainLooper()); 

    @Override 
    public void run() { 
     // ... 
     mHandler.post(new Runnable() { 
      public void run() { 
       locationResult.gotLocation(null); 
      } 
     }); 
     // ... 
    } 
} 

Answer 2

我试过这个...它的工作，希望它会帮助你..

protected class Asyctast extends AsyncTask<String, Integer, Integer> 
{ 

    @Override 
    protected Integer doInBackground(String... params) { 
     // TODO Auto-generated method stub 


     Log.d("Asynctask", ""+params); 
Looper.prepare(); 

     ImageThumbnailsActivity m = new ImageThumbnailsActivity(); 

      Toast.makeText(ImageThumbnailsActivity.this,""+params ,Toast.LENGTH_SHORT).show(); 
      final Dialog dialog_options = new Dialog(ImageThumbnailsActivity.this); 
      dialog_options.setContentView(R.layout.option); 
      dialog_options.show(); 
     Looper.loop(); 
     return null; 
    }  
}