Java的Swing JTree treeWillExpand事件计时 - 在扩展之前不更新swing元素

Question

我最近进入了java世界并开始了一个个人项目，但作为Java的新手，我在Java的Swing JTree组件中遇到了一个问题。

我的问题发生在“LoadingObserver”中的一个大型代码项目（https://github.com/adrian-tilita/jTreeHelper）中，所以，总结一下，我试图在3个文件中的一堆基本代码（无包）中复制问题：

主要

public class Main {
    public static void main(String[] args) {
        View.main(args);
    }
}

事件处理程序

import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeExpansionListener;
import javax.swing.event.TreeWillExpandListener;
import javax.swing.tree.ExpandVetoException;

public class EventHandler implements TreeWillExpandListener, TreeExpansionListener {
    private javax.swing.JLabel label;
    public void setLabel(javax.swing.JLabel label) {
        this.label = label;
    }

    @Override
    public void treeWillExpand(TreeExpansionEvent event) throws ExpandVetoException {
        this.label.setText("Loading...");
        try {
            Thread.sleep(1000);
        } catch (Exception e) {
            // do nothing
        }
    }

    @Override
    public void treeExpanded(TreeExpansionEvent event) {
        this.label.setText("Loaded");
    }

    @Override
    public void treeWillCollapse(TreeExpansionEvent event) throws ExpandVetoException {}

    @Override
    public void treeCollapsed(TreeExpansionEvent event) {}
}

查看

public class View extends javax.swing.JFrame {
    public View() {
        initComponents();
        EventHandler handler = new EventHandler();
        handler.setLabel(jLabel1);
        this.jTree1.addTreeWillExpandListener(handler);
        this.jTree1.addTreeExpansionListener(handler);
    }

    @SuppressWarnings("unchecked")
    private void initComponents() {
        jScrollPane1 = new javax.swing.JScrollPane();
        jTree1 = new javax.swing.JTree();
        jLabel1 = new javax.swing.JLabel();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        jScrollPane1.setViewportView(jTree1);
        jLabel1.setText("jLabel1");
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jScrollPane1)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 147, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(0, 233, Short.MAX_VALUE)))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(19, 19, 19)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 365, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addComponent(jLabel1)
                .addContainerGap(15, Short.MAX_VALUE))
        );
        pack();
    }

    public static void main(String args[]) {
        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(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(View.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new View().setVisible(true);
            }
        });
    }
    private javax.swing.JLabel jLabel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTree jTree1;
}

视图只是一个生成的netbeans表单，构造函数有几行。

当我尝试更新swing组件（加载）时，我遇到的问题是关于“treeWillExpand”事件，但在我的情况下，我只得到“加载”文本。

我做错了什么或事件不是我想要的事件？

主要是，我的问题是：如何在“TreeWillExpand”事件中更新Swing组件？

PS：温柔，这是我第一次遇到java。