Swing - 更新标签

Question

我有一个消息标签和一个提交按钮.将多次按下提交按钮,每次按下的操作最多可能需要一分钟.

按下按钮时,我想将消息设置为空,在任务完成后,我想将消息设置为"完成".

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

   doTheTask();

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

是否可以在submitActionPerformed()方法运行之前(或在方法中)更新该消息标签,但是在单击按钮之后？

Answer 1

虽然Swing并发教程已经包含了一些关于如何在Swing中处理并发性的非常好的示例,但是在下面找一个例子

• 包含一个复选框,用于证明UI仍处于活动状态
• 有一个进度条,从中更新 SwingWorker

• 有一个标签,一旦SwingWorker完成就会更新

  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();
        }
      }
    }
  }
  

Answer 2

是的,您可以使用SwingWorker线程执行此操作,执行所有预先submitActionPerformed()活动,例如更新标签,在execute()方法中使用worker currentThread调用doTheTask()作为后台作业Thread.

我建议您阅读本文档以获取有关SwingWorker Thread的参考