java - JProgressBar 不更新，找不到线索

Question

干得好，现在我只想知道为什么如果我在 while 循环中添加指令 System.out.println 下面的进度会同时显示在 Gui 中的 cmd 和 Pgbar 上？ :

while(progress < 99){ 
  System.out.println("into while of PBar Thread progress = "+progress); 
  if(progress != Path.operationProgress){ 
    operationProgressBar.setValue(progress); 
    progress = Path.operationProgress; 
    operationProgressBar.repaint(); } }

need some help around , i can't get the JProgressBar to update, i can't use SwingWorker, i have to solve this without it . the variable Path.operationProgress is a static variable from a "Path" class instance, and it's updated from another thread, so i think the PBar and Path instances are both executed in user's Threads and not in the EDT . here is the Code of the progress bar :

    import javax.swing.*;
    public class Pbar extends Thread {
      JProgressBar operationProgressBar;
      public Pbar(JProgressBar operationProgressBar) {
          this.operationProgressBar = operationProgressBar;
      }

      @Override
      public void run() {
          int progress = Path.operationProgress;
          while(progress < 99) {
              if(progress != Path.operationProgress) {
                  operationProgressBar.setValue(progress);
                  progress = Path.operationProgress;
                  operationProgressBar.repaint();
              }}}
     }

this is the action that launches the threads :

private javax.swing.JProgressBar operationProgressBar;
private javax.swing.JLabel pathImage;
private javax.swing.JButton simulatedAnnelingButton;

public class TSPGUI extends javax.swing.JFrame {

    TSPMG tspInstance;
    Path p, result;
    String filename = "";
    int neighborHood_Type = 1, i = 0;
    // ......Constructor Stuff and init()

private void simulatedAnnelingButtonActionPerformed(java.awt.event.ActionEvent evt)

{
Thread sa = new Thread(){ @Override public void run(){ result = p.SimulatedAnnealing(neighborHood_Type); String lastCostString = result.Cost() + ""; lastCostLabel.setText(lastCostString); }}; sa.start(); Pbar pb = new Pbar(operationProgressBar); pb.start(); } //Some other Stuff ... }

Answer 1

如果您不能使用 SwingWorker 则使用 SwingUtilities.invokeLater，例如:

if (progress != Path.operationProgress) {
    final int progressCopy = progress; // Probably not final so copy is needed
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        void run() {
            operationsProgressBar.setValue(progressCopy);
        }
    });
}

注意:执行此操作时，run 中使用的所有内容都必须是最终的，或者必须有其他措施来访问变量。此代码在这方面具有象征意义。

您需要在事件派发线程之外对 Swing 组件进行操作，这是没有办法解决的。