doInBackground（）中的致命异常

我试图演示一个AsyncTask和Asynctask中方法的执行顺序。我已经在每一种方法吐司吐司看到的顺序。以下是代码片段我用：doInBackground（）中的致命异常

private class UploadImage extends AsyncTask<Void, Void, Void> { 

    Bitmap image; 
    String name; 

    public UploadImage(Bitmap image, String name){ 
     this.image = image; 
     this.name = name; 

     Toast.makeText(getApplicationContext(), "Constructor - UpImg",Toast.LENGTH_SHORT).show(); 
    } 

    @Override 
    protected Void doInBackground(Void... arg0) { 

     Toast.makeText(getApplicationContext(), "DoinBgd - UpImg",Toast.LENGTH_SHORT).show(); 


/*  ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
     image.compress(Bitmap.CompressFormat.PNG, 100, baos); 
     String encodedImage = Base64.encodeToString(baos.toByteArray(), Base64.DEFAULT); 
     Toast.makeText(getApplicationContext(), "DoInBgd - UpImg",Toast.LENGTH_LONG).show(); 

     ArrayList<NameValuePair> dataToSend = new ArrayList(); 
     dataToSend.add(new BasicNameValuePair("image", encodedImage)); 
     dataToSend.add(new BasicNameValuePair("name", name)); 

     HttpParams httpRequestParams = getHttpRequestParams(); 
     HttpClient client = new DefaultHttpClient(httpRequestParams); 
     HttpPost post = new HttpPost(SERVERADDRESS + "/SavePicture.php"); 

     try{ 
      post.setEntity(new UrlEncodedFormEntity(dataToSend)); 
      client.execute(post); 
     }catch(Exception e) 
     { 
      e.printStackTrace(); 
     }*/ 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Void result) { 
     // TODO Auto-generated method stub 

     Toast.makeText(getApplicationContext(), "OnPost exec - UpImg",Toast.LENGTH_SHORT).show(); 
     super.onPostExecute(result); 
     //Toast.makeText(getApplicationContext(), "Image Uploaded" , Toast.LENGTH_SHORT).show(); 
    } 

    @Override 
    protected void onPreExecute() { 
     // TODO Auto-generated method stub 
     Toast.makeText(getApplicationContext(), "PreExec - UpImg",Toast.LENGTH_SHORT).show(); 
     /*ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
     image.compress(Bitmap.CompressFormat.PNG, 100, baos); 
     String encodedImage = Base64.encodeToString(baos.toByteArray(), Base64.DEFAULT); */ 
     super.onPreExecute(); 
    } 
}

在其他方法正确显示up.But，我得到的错误，当我把土司doInBac祝酒词...（）方法。以下是logcat的（）输出中：

05-17 10:38:51.888: E/AndroidRuntime(18508): FATAL EXCEPTION: AsyncTask #3 
05-17 10:38:51.888: E/AndroidRuntime(18508): java.lang.RuntimeException: An error occured while executing doInBackground() 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.os.AsyncTask$3.done(AsyncTask.java:299) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at java.util.concurrent.FutureTask.setException(FutureTask.java:219) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at java.util.concurrent.FutureTask.run(FutureTask.java:239) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at java.lang.Thread.run(Thread.java:856) 
05-17 10:38:51.888: E/AndroidRuntime(18508): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.os.Handler.<init>(Handler.java:197) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.os.Handler.<init>(Handler.java:111) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.widget.Toast$TN.<init>(Toast.java:324) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.widget.Toast.<init>(Toast.java:91) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at android.widget.Toast.makeText(Toast.java:238) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at com.msrohit.imageselect.MainActivity$UploadImage.doInBackground(MainActivity.java:191) 
05-17 10:38:51.888: E/AndroidRuntime(18508): at com.msrohit.imageselect.MainActivity$UploadImage.doInBackground(MainActivity.java:1)

什么是背后的RuntimeException的原因是什么？

来源

2016-05-17 Rohit S

不能更新UI线程从doinbackground方法，这就是为什么你gettting这个错误，你必须从doinbackground方法 –

删除吐司，并检查这个http://stackoverflow.com/questions/11936048/android-asynctask-cant-create-handler-inside-线程那不是所谓的looper – jayeshsolanki93

好吧...我会尽力回复你... –

你不能触及doinbackground UI线程，而不是使用像onPostExecute或runOnUiThread方法或简单地将消息发送到一个handlee从doInBackground内更新你的进步：

runOnUiThread(new Runnable() { 
      public void run() { 
      //Do something on UiThread 
     } 
    });

来源

2016-05-17 10:56:46

doInBackground（）中的致命异常

回答

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