Android：線程停止工作

Question

它從通道讀取圖像並將其寫入卡。卡中的圖像是完全寫入的，很好。唯一的問題是線程被掛起，並且在該循環之後不執行任何行。

protected Bitmap doInBackground(String... arg0) { 
    // TODO Auto-generated method stub' 
     // Runtime.getRuntime().availableProcessors(); 
    System.out.println("Inside doinback"+ RemoteScreen.out.toString()); 
     try { 
      RemoteScreen.out.write(210); 
      //Home.threadloop = false; 
      Bitmap bitmap = null; 
      String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath(); 
      String fileName = "a.png"; 
      String imageInSD = baseDir + File.separator + fileName; 
       System.out.println(imageInSD); 
      if (is!= null) { 
       FileOutputStream fos = null; 
       BufferedOutputStream bos = null; 
       try { 
        // Log.i("IMSERVICE", "FILERECCC-1"); 
        //ContextWrapper context = null; 
        fos = new FileOutputStream(imageInSD); 
        bos = new BufferedOutputStream(fos); 

        byte[] aByte = new byte[1024]; 
        int bytesRead; 
        //thread stuck in this loop and does not move forward 
        while ((bytesRead = is.read(aByte)) > 0 ) { 
         if (bytesRead == 1) 
          break; 
         bos.write(aByte, 0, bytesRead); 
        System.out.println("Loop"+aByte); 

        } 

        bos.close(); 

       Log.i("IMSERVICE", "out of loop");  
        java.io.FileInputStream in = new FileInputStream(imageInSD); 
       bitmap = BitmapFactory.decodeStream(in); 
        bitmap = BitmapFactory.decodeFile(imageInSD); 

      Log.i("IMSERVICE", "saved"); 
       if (bitmap != null) 
        System.out.println(bitmap.toString()); 

       } catch (IOException ex) {  
        // Do exception handling  
      //  Log.i("IMSERVICE", "exception "); 
       } 
      } 
      publishProgress(b); 
      b = null; 
      ch = 4646; 

     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 



    return null; 
} 

日誌跟蹤顯示以下錯誤。

05-10 20:34:42.715: E/AndroidRuntime(1135): FATAL EXCEPTION: AsyncTask #3 
    05-10 20:34:42.715: E/AndroidRuntime(1135): java.lang.RuntimeException: An error occured while executing doInBackground() 
    05-10 20:34:42.715: E/AndroidRuntime(1135): at android.os.AsyncTask$3.done(AsyncTask.java:299) 
    05-10 20:34:42.715: E/AndroidRuntime(1135):  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352) 
    05-10 20:34:42.715: E/AndroidRuntime(1135): at java.util.concurrent.FutureTask.setException(FutureTask.java:219) 
    05-10 20:34:42.715: E/AndroidRuntime(1135):  at java.util.concurrent.FutureTask.run(FutureTask.java:239) 
    05-10 20:34:42.715: E/AndroidRuntime(1135):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
    05-10 20:34:42.715: E/AndroidRuntime(1135): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 
05-10 20:34:42.715: E/AndroidRuntime(1135): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 
05-10 20:34:42.715: E/AndroidRuntime(1135): at java.lang.Thread.run(Thread.java:856) 
05-10 20:34:42.715: E/AndroidRuntime(1135): Caused by: java.lang.NullPointerException 
05-10 20:34:42.715: E/AndroidRuntime(1135): at com.rms.remotedesktop1.screencahnge.doInBackground(screencahnge.java:43) 
05-10 20:34:42.715: E/AndroidRuntime(1135): at com.rms.remotedesktop1.screencahnge.doInBackground(screencahnge.java:1) 
05-10 20:34:42.715: E/AndroidRuntime(1135): at android.os.AsyncTask$2.call(AsyncTask.java:287) 
05-10 20:34:42.715: E/AndroidRuntime(1135): at java.util.concurrent.FutureTask.run(FutureTask.java:234) 

Answer 1

根據logcat，代碼在第43行崩潰與空指針異常，我不知道哪一行是43。但是：

• 您是否檢查過Environment.getExternalStorageDirectory().getAbsolutePath()正在返回非null？它可能沒有外部存儲目錄，或者你沒有權限知道它。
• 它也值得閱讀開發者頁面，http://developer.android.com/reference/android/os/Environment.html#getExternalStorageDirectory()，它注意你不應該寫入目錄，你似乎正在做。

Answer 2

我自己解決了這個問題。由於代碼中的邏輯錯誤，正在更改其值的靜態變量出現錯誤。