java jLabel.setVisible 不工作

Question

我想检测监视器的数量，并显示相同数量的标签。但 setvisible 不起作用。 InitialMonitorsDetection - 我想隐藏每个标签，在 DetectMonitors 中 - 显示一些标签，但标签始终可见。我是java新手，很抱歉提出这个愚蠢的问题。谢谢你的帮助。 `

   public MainFrame() {        initComponents();            }
    public void InititalMonitorsDetection() {             
    Monitor1.setVisible(false);
    Monitor2.setVisible(false);
    Monitor3.setVisible(false);
    Monitor4.setVisible(false);
    Monitor5.setVisible(false);
    Monitor6.setVisible(false);
    Monitor7.setVisible(false);
    Monitor8.setVisible(false);
    Monitor9.setVisible(false);
    Monitor10.setVisible(false);

    }

    public void DetectMonitors() {

    JLabel[] ArMonitors;
    ArMonitors = new JLabel[11];
    ArMonitors[1] = Monitor1;
    ArMonitors[2] = Monitor2;
    ArMonitors[3] = Monitor3;
    ArMonitors[4] = Monitor4;
    ArMonitors[5] = Monitor5;
    ArMonitors[6] = Monitor6;
    ArMonitors[7] = Monitor7;
    ArMonitors[8] = Monitor8;
    ArMonitors[9] = Monitor9;
    ArMonitors[10] = Monitor10;

      GraphicsEnvironment ge = GraphicsEnvironment.
      getLocalGraphicsEnvironment();
      GraphicsDevice[] gs = ge.getScreenDevices();
      System.out.println(gs.length);

      for (int i=1; i <= gs.length; i++){
         ArMonitors[i].setVisible(true);
      }


      }

    public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting     code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the    default look and feel.
     * For details see   http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(MainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */




    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new MainFrame().setVisible(true);

        }
    });


    MainFrame mainfr = new MainFrame();
    mainfr.InititalMonitorsDetection();
    mainfr.DetectMonitors();<code>`             

Answer 1

所有 UI 操作都需要通过事件调度程序线程 (EDT) 来完成。您需要删除此 block :

MainFrame mainfr = new MainFrame();
mainfr.InititalMonitorsDetection();
mainfr.DetectMonitors();

将其放在这里(至少):

java.awt.EventQueue.invokeLater(new Runnable() {
    public void run() {
         MainFrame mainfr = new MainFrame();
         mainfr.InititalMonitorsDetection();
         mainfr.DetectMonitors();
    }
});

理想情况下，您可以将逻辑与 UI 操作分开。上面的代码段将在 EDT 上运行所有内容，这可能会对应用程序的响应能力产生负面影响，具体取决于您正在进行的操作的持续时间。