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AsyncTask和Looper.prepare()错误

looper android-asynctask android

31

Lee Armstrong · 技术社区 · 15 年前

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;
    }
}

这在一些测试设备上似乎工作得很好,但是我看到开发人员控制台上出现了很多错误。我好像不知道为什么要把这个活套放在哪里。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)

按请求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);
    }
}

2 回复 | 直到 15 年前

1

95

Timo Ohr 15 年前

长话短说:

AsyncTask 内部使用 Handler . 处理程序基本上允许您发布 Runnables 从处理程序被分配到的线程上的另一个线程,在这种情况下 异步任务 总是调用它的线程。这只适用于具有 Looper 准备好了。

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

短篇故事:

只需将每个呼叫包装到 FinderMain$1.gotLocation 或创造 异步任务 在它的内部 Runnable ,并将其发布到 经办人 绑定到UI线程,如下所示:

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);
          }
       });
       // ...
     }
}

2

18

Nilesh Tupe 14 年前

我试过了…它成功了,希望它能帮助你。。

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;
    }       
}