在等待未来完成时未显示进度条

Question

我正在编写一些代码以发现Android中处理异步的不同方式，而且我已经完成了AsyncTask，现在我已经有了过去的未来，但是这一次它让我有点...

代码本身工作正常，除了（旋转）进度条只在下载操作完成后才显示的事实......尽管我告诉代码之前显示它...

下面的代码：

public void startDownload(final String url) { 
    bar.setVisibility(View.VISIBLE); // progress bar should appear here 

    ExecutorService pool = Executors.newCachedThreadPool(); 
    Gson gson = new Gson(); 

    Future<String> promise = pool.submit(new Callable<String>() { 
     @Override 
     public String call() throws Exception { 
      String response = ""; 
      DefaultHttpClient client = new DefaultHttpClient(); 
      HttpGet httpGet = new HttpGet(url); 
      try { 
       HttpResponse execute = client.execute(httpGet); 
       InputStream content = execute.getEntity().getContent(); 

       BufferedReader buffer = new BufferedReader(new InputStreamReader(content)); 

       String s = ""; 

       while((s = buffer.readLine()) != null) response += s; 

      } catch (IOException ioe) { 
       ioe.printStackTrace(); 
      } 
      return response; 
     } 
    }); 


    while(promise.isDone() == false) { 
     // wait 
    } 

    bar.setVisibility(View.GONE); // and disappear here 

    try { 
     GitHubStatus status = gson.fromJson(promise.get(), GitHubStatus.class); 

     statusText.setText(status.getStatus()); 
     bodyText.setText(status.getBody()); 
     dateText.setText(status.getCreationDate()); 
    } catch (ExecutionException ee) { 
     ee.printStackTrace(); 
    } catch (InterruptedException ie) { 
     ie.printStackTrace(); 
    } 

    // instead it briefly appears here, and then disappears again 
} 

对于那些不知道的人;期货执行自己，因此你不需要调用“运行”或“开始”方法来启动它

我试图把一个Log.v("DEBUG: ", "Loading...");在等待它完成的循环中，它确实打印邮件就好，很多时候在那个

我没有试过循环，那也不行，而且我甚至有ProgressDialog，不能正常工作，尝试...

我知道我无法在UI线程忙时更新UI线程，但我只在UI线程中的任何工作完成之前和之后设置了可见性，所以这里有什么问题？为什么它不工作？

Answer 1

尝试以下操作：

public void startDownload(final String url) { 
    bar.setVisibility(View.VISIBLE); // progress bar should appear here 

    ExecutorService pool = Executors.newCachedThreadPool(); 
    Gson gson = new Gson(); 

    Future<String> promise = pool.submit(new Callable<String>() { 
     @Override 
     public String call() throws Exception { 
      String response = ""; 
      DefaultHttpClient client = new DefaultHttpClient(); 
      HttpGet httpGet = new HttpGet(url); 
      try { 
       HttpResponse execute = client.execute(httpGet); 
       InputStream content = execute.getEntity().getContent(); 

       BufferedReader buffer = new BufferedReader(new InputStreamReader(content)); 

       String s = ""; 

       while((s = buffer.readLine()) != null) response += s; 

      } catch (IOException ioe) { 
       ioe.printStackTrace(); 
      } 

      runOnUiThread(new Runnable() 
      { 
       public void run() 
       { 
        bar.setVisibility(View.GONE); // and disappear here 

        try { 
         GitHubStatus status = gson.fromJson(promise.get(), GitHubStatus.class); 

         statusText.setText(status.getStatus()); 
         bodyText.setText(status.getBody()); 
         dateText.setText(status.getCreationDate()); 
        } catch (ExecutionException ee) { 
         ee.printStackTrace(); 
        } catch (InterruptedException ie) { 
         ie.printStackTrace(); 
        } 
       } 
      });  
      return response; 
     } 
    }); 
} 

由于

while(promise.isDone() == false) { 
      // wait 
     } 

你阻挡UIThread。