可能是您更新了错误的字符串或设置了不正确的标签文本。两者都是必需的。在下面的示例（使用您的名称）中，两个更新在按钮的中紧密结合
actionPerformed()。这里显示了一种更宽松的耦合方法。
import java.awt.EventQueue;import java.awt.GridLayout;import java.awt.event.ActionEvent;import javax.swing.AbstractAction;import javax.swing.JButton;import javax.swing.Jframe;import javax.swing.JLabel;import javax.swing.JPanel;public class JavaGUI extends JPanel { private Control control = new Control(); private Keys keys = new Keys("Original starting value."); public JavaGUI() { this.setLayout(new GridLayout(0, 1)); this.add(keys); this.add(control); } private class Control extends JPanel { public Control() { this.add(new JButton(new AbstractAction("Update") { @Override public void actionPerformed(ActionEvent e) { System.out.println("Command: " + e.getActionCommand()); keys.string = String.valueOf(System.nanoTime()); keys.label.setText(keys.string); } })); } } private class Keys extends JPanel { private String string; private JLabel label = new JLabel(); public Keys(String s) { this.string = s; label.setText(s); this.add(label); } } private void display() { Jframe f = new Jframe("JavaGUI"); f.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE); f.add(this); f.pack(); f.setLocationRelativeTo(null); f.setVisible(true); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { new JavaGUI().display(); } }); }}
