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上工作正常，但我发现在开发控制台上出现了很多错误。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

长篇故事：

AsyncTask内部使用Handler。处理程序基本上允许您从处理程序分配给的线程上的另一个线程发布Runnables，在AsyncTask的情况下，它始终是调用它的线程。这仅适用于已准备Looper的线程。

有关详细信息，请参阅http://developer.android.com/reference/android/os/Handler.html

短篇小说：

只需将FinderMain$1.gotLocation中的每个调用或AsyncTask中的Runnable包围，并将其发布到绑定到UI线程的Handler，就像这样：

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......它很有用，希望它能帮到你......

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;
    }       
}

AsyncTask和Looper.prepare（）错误

2 个答案: