package com.ttc;

import java.awt.Button;
import java.awt.Dialog;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.JobAttributes.DialogType;
import java.awt.Label;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class test6 extends Frame implements ActionListener
{
static Frame frm = new Frame();
static Label welcome = new Label("请关闭对话框");
static Dialog dlg = new Dialog(frm);
static Button Close_btn = new Button("关闭");
static Button Cancel_btn = new Button("取消");
static WinLis wlis = new WinLis();
public static void main (String args[])
{
frm.setTitle("Dialog");
frm.setSize(200,150);
frm.setLocation(200, 200);
welcome.setAlignment(Label.CENTER);
dlg.setTitle("你确定要关闭？");
dlg.setSize(160, 120);
dlg.setLayout(new FlowLayout(FlowLayout.CENTER,5,30));
dlg.add(Close_btn);
dlg.add(Cancel_btn);
Close_btn.addActionListener((ActionListener) frm);
Cancel_btn.addActionListener((ActionListener) frm);
frm.addWindowListener(wlis);
frm.setVisible(true);
}
static class WinLis extends WindowAdapter
{
public void windowClosing(WindowEvent e)
{
dlg.setLocation(230, 200);
dlg.show();
}
}
public void actionPerformed(ActionEvent e)
{
Button btn = (Button)e.getSource();
if(btn == Close_btn)
{
dlg.dispose();
frm.dispose();
}
else if(btn == Cancel_btn);
dlg.hide();
}
}
为什么会报
Exception in thread "main" java.lang.ClassCastException: java.awt.Frame
        at com.ttc.test6.main(test6.java:33)

Frame 并没有实现ActionListener接口，你定义的类test6才实现了ActionListener接口，看代码注释：

1. package com.ttc;
   
2. 
   
3. import java.awt.Button;
   
4. import java.awt.Dialog;
   
5. import java.awt.FlowLayout;
   
6. import java.awt.Frame;
   
7. import java.awt.JobAttributes.DialogType;
   
8. import java.awt.Label;
   
9. import java.awt.event.ActionEvent;
   
10. import java.awt.event.ActionListener;
    
11. import java.awt.event.ComponentListener;
    
12. import java.awt.event.WindowAdapter;
    
13. import java.awt.event.WindowEvent;
    
14. public class test6 extends Frame implements ActionListener
    
15. {
    
16. static Frame frm = new Frame();//你这里用的是Frame来构造 frm对象，Fram没有实现ActionListener接口
    
17. static Label welcome = new Label("请关闭对话框");
    
18. static Dialog dlg = new Dialog(frm);
    
19. static Button Close_btn = new Button("关闭");
    
20. static Button Cancel_btn = new Button("取消");
    
21. static WinLis wlis = new WinLis();
    
22. public static void main (String args[])
    
23. {
    
24. frm.setTitle("Dialog");
    
25. frm.setSize(200,150);
    
26. frm.setLocation(200, 200);
    
27. welcome.setAlignment(Label.CENTER);
    
28. dlg.setTitle("你确定要关闭？");
    
29. dlg.setSize(160, 120);
    
30. dlg.setLayout(new FlowLayout(FlowLayout.CENTER,5,30));
    
31. dlg.add(Close_btn);
    
32. dlg.add(Cancel_btn);
    
33. Close_btn.addActionListener((ActionListener) frm);//Fram没有实现ActionListener接口，无法转换类型
    
34. Cancel_btn.addActionListener((ActionListener) frm);//Fram没有实现ActionListener接口，无法转换类型
    
35. frm.addWindowListener(wlis);
    
36. frm.setVisible(true);
    
37. }
    
38. static class WinLis extends WindowAdapter
    
39. {
    
40. public void windowClosing(WindowEvent e)
    
41. {
    
42. dlg.setLocation(230, 200);
    
43. dlg.show();
    
44. }
    
45. }
    
46. public void actionPerformed(ActionEvent e)
    
47. {
    
48. Button btn = (Button)e.getSource();
    
49. if(btn == Close_btn)
    
50. {
    
51. dlg.dispose();
    
52. frm.dispose();
    
53. }
    
54. else if(btn == Cancel_btn);
    
55. dlg.hide();
    
56. }
    
57. }
    

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