獲取無法在未調用Looper.prepare（）和代碼的Android線程中創建處理程序4

Question

我已經搜索了許多類似的問題和答案，但我仍然無法理解爲什麼我的代碼拋出這個錯誤。

12-27 12:57:57.908: W/dalvikvm(465): Exception Ljava/lang/RuntimeException; thrown while initializing Landroid/os/AsyncTask; 
12-27 12:57:57.908: W/dalvikvm(465): threadid=9: thread exiting with uncaught exception (group=0x40014760) 
12-27 12:57:57.927: E/AndroidRuntime(465): FATAL EXCEPTION: Thread-10 
12-27 12:57:57.927: E/AndroidRuntime(465): java.lang.ExceptionInInitializerError 
12-27 12:57:57.927: E/AndroidRuntime(465): at com.verious.baseballnews.NewsParser.fetchNews(NewsParser.java:137) 
12-27 12:57:57.927: E/AndroidRuntime(465): at com.verious.baseballnews.MLBNews.getLeagueNews(MLBNews.java:145) 
12-27 12:57:57.927: E/AndroidRuntime(465): at com.verious.baseballnewsreader.BaseballNewsReader.licenseCheckCompleted(BaseballNewsReader.java:45) 
12-27 12:57:57.927: E/AndroidRuntime(465): at com.verious.lm.LicenseMgr.respondFromCache(LicenseMgr.java:218) 
12-27 12:57:57.927: E/AndroidRuntime(465): at com.verious.lm.LicenseMgr.run(LicenseMgr.java:139) 
12-27 12:57:57.927: E/AndroidRuntime(465): at java.lang.Thread.run(Thread.java:1020) 
12-27 12:57:57.927: E/AndroidRuntime(465): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 
12-27 12:57:57.927: E/AndroidRuntime(465): at android.os.Handler.<init>(Handler.java:121) 
12-27 12:57:57.927: E/AndroidRuntime(465): at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:595) 
12-27 12:57:57.927: E/AndroidRuntime(465): at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:595) 
12-27 12:57:57.927: E/AndroidRuntime(465): at android.os.AsyncTask.<clinit>(AsyncTask.java:184) 
12-27 12:57:57.927: E/AndroidRuntime(465): ... 6 more 

有兩個困惑我這裏有：

1. 我的代碼工作與Android 4.0，但得到了錯誤的所有「不能內螺紋已不叫Looper.prepare創建處理程序」較低的版本。
2. 即使當我清空doInBackground（）調用，因此它只返回一個「」，我仍然有錯誤。

我想從使用AsyncTask的Web服務中獲取一些消息並在視圖中顯示它們。這裏是我的基本代碼：

public class News { 

    ... 
    new FetchXML().execute(url); 
    ... 

    private class FetchXML extends AsyncTask<String,String,String> { 
    protected String doInBackground(final String... urls) { 

     String urlToOpen = urls[0]; 

     URL url; 
     String inputLine = null; 
     String response = ""; 
     URLConnection connection; 

     try { 
      String authStringEnc = b64encode("user:pass".getBytes()); 
         url = new URL(urlToOpen); 
      connection = url.openConnection(); 
      connection.setRequestProperty("Authorization", "Basic " + authStringEnc); 

      BufferedReader in = new BufferedReader(
       new InputStreamReader(
       connection.getInputStream())); 

      while ((inputLine = in.readLine()) != null) { 
       response += inputLine; 
      } 
      in.close(); 
     } catch(MalformedURLException e) { 
      // 
     } catch(IOException e) { 
      // 
     } 

     return response; 
    } 

    protected void onPostExecute(String result) { 
     super.onPostExecute(result); 
     NewsParser.this.parse(result); 
    } 
} 

NewsParser parse（）方法分析xml並更新視圖。

我在這裏完全損失。任何幫助將不勝感激！

謝謝！

Answer 1

您正在創建AsyncTask實例並從後臺線程執行它。您只能從主應用程序線程創建並執行AsyncTask實例。