的Android主題/的AsyncTask，和的ExceptionInInitializerError RuntimeException的關於「runOnUiThread」

Question

我需要用兩個錯誤I'm混得

1. 創建線程，在那裏我真的創建文件
2. 文件後您的幫助的東西，一個得到的AsyncTask執行將文件發送到服務器（多/表單數據）

那是第一部分的樣子：

public void startResultTransfer(final int timestamp, final int duration, final String correction, final float textSize, final int age, final int switch_count, final Activity activity){ 

    synchronized(DataTransmission.class){ 

     new Thread() { 
      public void run() { 
       FileWriter fw = null; 
       //1.Check if file exists 
       File file = new File(FILE_PATH); 
       if(!file.exists()){ 
        //File does not exists, when we have to generate the head-line 
        try { 
         fw = new FileWriter(FILE_PATH); 
         fw.append("timestamp\tduration\tcorrection\ttext_size\tage\tswitch_count"); //Headline 
        } catch (IOException e) { 
         // TODO Auto-generated catch block 
         e.printStackTrace(); 
        } 
       } 
       //2. Write Result 
       try { 
        if(fw == null) 
         fw = new FileWriter(FILE_PATH); 
        fw.append("\n"+String.valueOf(timestamp)+"\t"); 
        fw.append(""+String.valueOf(duration)+"\t"); 
        fw.append(""+correction+"\t"); 
        fw.append(""+String.valueOf(textSize)+"\t"); 
        fw.append(""+String.valueOf(age)+"\t"); 
        fw.append(""+String.valueOf(switch_count)+"\t"); 
        fw.close(); 
       } catch (IOException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 

       //3. File Transfer 
       if(isOnline(activity)) 
        transferFileToServer(activity); 
      } 
     }.start(); 

    } 
} 

功能 「transferFileToServer」 看起來是這樣的：

public synchronized void transferFileToServer(Activity activity){ 
    String id = id(activity); 
    File file = new File(FILE_PATH); 

    if(id != null && file.exists()){ 
     final String url = URL+id; 
     activity.runOnUiThread(new Runnable() { 
      @Override 
      public void run() { 
       TransmissionTask task = new TransmissionTask(); 
       task.execute(url); 
      } 
     }); 

    } 

} 

現在，我真的收到 「的ExceptionInInitializerError」 通過了java.lang.RuntimeException造成無法創建解釋性信息

處理程序內部線程沒有調用Looper.prepare（）「

在行」activity.runOnUiThread「。

在第一個函數中，我需要在一些預先設置後調用「transferFileToServer」。但函數也應該從第一個函數中獨立地調用。

我應該實現一個MessageHandler來執行線程末尾的AsyncTask嗎？ http://developer.android.com/reference/android/os/Looper.html

或者我應該將「transferFileToServer」函數中的「AsyncTask」更改爲一個線程，因爲我不做任何UI操作？

編輯：該方法從異步任務

開始

class TransmissionTask extends AsyncTask<String, Void, String> { 

    public TransmissionTask() { 

    } 

    @Override 
    protected String doInBackground(String... params) { 
     synchronized(DataTransmission.class){ 
      try { 

       HttpURLConnection urlConn; 
       java.net.URL mUrl = new java.net.URL(params[0]); 
       urlConn = (HttpURLConnection) mUrl.openConnection(); 
       urlConn.setDoOutput(true); 
       urlConn.setRequestMethod("POST"); 

       String boundary = "---------------------------14737809831466499882746641449"; 
       String contentType = "multipart/form-data; boundary="+boundary; 
       urlConn.addRequestProperty("Content-Type", contentType); 

       DataOutputStream request = new DataOutputStream(urlConn.getOutputStream()); 
       request.writeBytes("\r\n--"+boundary+"\r\n"); 
       request.writeBytes("Content-Disposition: form-data; name=\"userfile\"; filename=\""+FILE_NAME+"\"\r\n"); 
       request.writeBytes("Content-Type: application/octet-stream\r\n\r\n"); 

       File myFile = new File(FILE_PATH); 
       int size = (int) myFile.length(); 
       byte[] bytes = new byte[size]; 
       try { 
        BufferedInputStream buf = new BufferedInputStream(new FileInputStream(myFile)); 
        buf.read(bytes, 0, bytes.length); 
        buf.close(); 
       } catch (FileNotFoundException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
       request.write(bytes); 
       request.writeBytes("\r\n--"+boundary+"--\r\n"); 

       request.flush(); 
       request.close(); 

       InputStream responseStream = new BufferedInputStream(urlConn.getInputStream()); 

       BufferedReader responseStreamReader = new BufferedReader(new InputStreamReader(responseStream)); 
       String line = ""; 
       StringBuilder stringBuilder = new StringBuilder(); 
       while ((line = responseStreamReader.readLine()) != null) 
       { 
        stringBuilder.append(line).append("\n"); 
       } 
       responseStreamReader.close(); 

       String response = stringBuilder.toString(); 
       responseStream.close(); 
       urlConn.disconnect(); 

       return response; 

      } catch (Exception e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(String result) { 
     super.onPostExecute(result); 

     if(result != null){ 
      if(result.toLowerCase().contains("erfolgreich")){ 
      //If successfull delete File 
      File file = new File(FILE_PATH); 
      file.delete(); 
      } 
     } 

    } 

} 

Answer 1

刪除runOnUiThread：

public synchronized void transferFileToServer(Activity activity){ 
String id = id(activity); 
File file = new File(FILE_PATH); 

if(id != null && file.exists()){ 
    final String url = URL+id; 

     TransmissionTask task = new TransmissionTask(); 
     task.execute(url); 
    } 
} 

的AsyncTask的主要思想，而不線程或處理程序運行後臺操作/邏輯。

你不需要包裝AsyncTask額外的線程與UI線程你做了什麼

從你的代碼綁定：

public void startResultTransfer(/* ... */){ 

.... 

new Thread() { 

    ..... 
    transferFileToServer(/* ... */); // its wrong!!! 
    .... 


}.start() 

} 

transferFileToServer啓動您AsyncTask，你在主UI線程中運行它不但在單線程。

這是一個問題。

從活動開始您的AsyncTask。