ProgressDialog不会显示，直到它太迟

Question

我正在写一个活动，它通过HTTP从Web获取一些XML，然后将其解析为一个DOM。然后它从DOM中提取一些必需的数据。

您可以想象，这需要一些时间，因此我将该代码放入它自己的线程中，然后尝试设置ProgressDialog以在用户等待完成时显示。

问题是ProgressDialog根本不显示。如果我删除电话解雇（），那么它显示的工作完成之后，很明显，只是坐在那里......

这里是我的代码：

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    progressDialog = ProgressDialog.show(this, "", "Loading...", true); 
    Thread downloadThread = new Thread(new DownloadVerseThread()); 
    downloadThread.start(); 
    setContentView(R.layout.main); 
    TextView verseView = (TextView) findViewById(R.id.displayFighterVerse); 
    TextView dateView = (TextView) findViewById(R.id.displayDateRange); 
    TextView referenceView = (TextView) findViewById(R.id.displayReference); 
    try { 
     downloadThread.join(); 
    } catch (InterruptedException e) { 
     Log.e(TAG, "Attempted to set the UI values before we were ready."); 
     return; 
    } 
    Log.d(TAG, "Date: " + date); 
    Log.d(TAG, "Reference: " + reference); 
    Log.d(TAG, "Scripture: " + scripture); 
    progressDialog.dismiss(); 
    dateView.setText(date); 
    referenceView.setText(reference); 
    verseView.setText(scripture); 
} 



private class DownloadVerseThread implements Runnable { 


    @Override 
    public void run() { 

     try { 
      FighterVerseDownloader downloader = new FighterVerseDownloader(); 
      date = downloader.getDateRange(); 
      reference = downloader.getReference(); 
      scripture = downloader.getScripture(); 
     } catch (FighterVersesException e) { 
      Log.e("FighterVerses", "Failed to get the Fighter Verse", e); 
     }   
    } 

} 

的FighterVersesDownloader的构造是哪里所有关于HTTP和DOM的工作都已完成。

关于我失踪的任何想法？我在使用AsyncTask时看到了一些类似的线程，但我想直接使用优秀的老式线程，并且建议的解决方案不适用。

Answer 1

我认为这个问题可能与你如何进行线程有关。当你调用downloadThread.join（）时，你基本上会花费那些代价昂贵的代码，并将它放在方法的中间，阻塞进程中的UI线程。

当线程完成时，您需要使用回调方法来处理UI更改。你的代码应该是这个样子：

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    progressDialog = ProgressDialog.show(this, "", "Loading...", true); 
    Thread downloadThread = new Thread(new DownloadVerseThread()); 
    Handler downloadHandler = new Handler(); 
    Runnable downloadCallback = new Runnable(){ 
     public void run(){ 
       setContentView(R.layout.main); 
      TextView verseView = (TextView) findViewById(R.id.displayFighterVerse); 
      TextView dateView = (TextView) findViewById(R.id.displayDateRange); 
      TextView referenceView = (TextView) findViewById(R.id.displayReference); 
      Log.d(TAG, "Date: " + date); 
      Log.d(TAG, "Reference: " + reference); 
      Log.d(TAG, "Scripture: " + scripture); 
      progressDialog.dismiss(); 
      dateView.setText(date); 
      referenceView.setText(reference); 
      verseView.setText(scripture); 
     } 
    }; 
    downloadThread.start(); 
} 

private class DownloadVerseThread implements Runnable { 
    @Override 
    public void run() { 

     try { 
      FighterVerseDownloader downloader = new FighterVerseDownloader(); 
      date = downloader.getDateRange(); 
      reference = downloader.getReference(); 
      scripture = downloader.getScripture(); 
      downloadHandler.post(downloadCallback); 
     } catch (FighterVersesException e) { 
      Log.e("FighterVerses", "Failed to get the Fighter Verse", e); 
     }   
    } 
} 

这将保持在下载后台线程，直到它完成，而不是几乎立即分流它放回UI线程，因为它是以前。编辑：Here's where I learned this。

Answer 2

我会推荐使用AsyncTask这种事情。