Swing - 更新標籤

Question

我有一個消息標籤和一個提交按鈕。提交按鈕將被多次按下，每次按下的操作可能需要一分鐘時間。

按下按鈕時，我想將消息設置爲空，並且在任務完成後，我要將消息設置爲「完成」。

private void submitActionPerformed(java.awt.event.ActionEvent evt) { 
    message = ""; 
    updateMessageLabel(); 

    doTheTask(); 

    /* this update is apply to the label after completion */ 
    message = "Complete"; 
} 

是否有可能在運行submitActionPerformed()方法之前（或方法）來更新該消息的標籤，但在點擊該按鈕後？

Answer 1

是的，你可以做到這一點使用SwingWorker線程，不喜歡更新標籤，在currentThread的​​方法中的所有預submitActionPerformed()活動和使用職工Thread調用doTheTask()作爲後臺作業。

我建議你去通過這個文檔，參考有關SwingWorker Thread

Answer 2

雖然Swing concurrency tutorial已經包含了如何應對搖擺併發一些很好的樣本，找到下面這

• 包含一個示例用於證明UI仍然存在的複選框
• 有一個進度條，它從SwingWorker更新爲

• 都有一個標籤，它獲取一旦SwingWorker更新完成

  import javax.swing.JCheckBox; 
  import javax.swing.JFrame; 
  import javax.swing.JLabel; 
  import javax.swing.JProgressBar; 
  import javax.swing.SwingWorker; 
  import java.awt.BorderLayout; 
  import java.awt.EventQueue; 
  import java.lang.reflect.InvocationTargetException; 
  import java.util.List; 
  import java.util.concurrent.ExecutionException; 
  
  public class SwingWorkerExample { 
      private static JProgressBar PROGRESS_BAR; 
      private static JLabel OUTPUT_LABEL; 
      private static JFrame createGUI(){ 
      JFrame testFrame = new JFrame("TestFrame"); 
  
      PROGRESS_BAR = new JProgressBar(); 
      PROGRESS_BAR.setMinimum(0); 
      PROGRESS_BAR.setMaximum(100); 
  
      OUTPUT_LABEL = new JLabel("Processing"); 
  
      testFrame.getContentPane().add(PROGRESS_BAR, BorderLayout.CENTER); 
      testFrame.getContentPane().add(OUTPUT_LABEL, BorderLayout.SOUTH); 
  
      //add a checkbox as well to proof the UI is still responsive 
      testFrame.getContentPane().add(new JCheckBox("Click me to proof UI is responsive"), BorderLayout.NORTH); 
  
  
  
      testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      return testFrame; 
      } 
  
      public static void main(String[] args) throws InvocationTargetException, InterruptedException { 
      EventQueue.invokeAndWait(new Runnable() { 
       @Override 
       public void run() { 
       JFrame frame = createGUI(); 
  
       frame.pack(); 
       frame.setVisible(true); 
       } 
      }); 
      //start the SwingWorker outside the EDT 
      MySwingWorker worker = new MySwingWorker(PROGRESS_BAR, OUTPUT_LABEL); 
      worker.execute(); 
      } 
      private static class MySwingWorker extends SwingWorker<String, Double>{ 
      private final JProgressBar fProgressBar; 
      private final JLabel fLabel; 
      private MySwingWorker(JProgressBar aProgressBar, JLabel aLabel) { 
       fProgressBar = aProgressBar; 
       fLabel = aLabel; 
      } 
  
      @Override 
      protected String doInBackground() throws Exception { 
       int maxNumber = 10; 
       for(int i = 0; i < maxNumber; i++){ 
       Thread.sleep(2000);//simulate long running process 
       double factor = ((double)(i+1)/maxNumber); 
       System.out.println("Intermediate results ready"); 
       publish(factor);//publish the progress 
       } 
       return "Finished"; 
      } 
  
      @Override 
      protected void process(List<Double> aDoubles) { 
       //update the percentage of the progress bar that is done 
       int amount = fProgressBar.getMaximum() - fProgressBar.getMinimum(); 
       fProgressBar.setValue((int) (fProgressBar.getMinimum() + (amount * aDoubles.get(aDoubles.size() - 1)))); 
      } 
  
      @Override 
      protected void done() { 
       try { 
       fLabel.setText(get()); 
       } catch (InterruptedException e) { 
       e.printStackTrace(); 
       } catch (ExecutionException e) { 
       e.printStackTrace(); 
       } 
      } 
      } 
  }