package javaclass;
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
public class ComponentEvents extends JFrame implements ActionListener
{
JButton b1=new JButton("改变框架的主题.");
JButton b2=new JButton("还原框架的主题");
JButton btnColor=new JButton("改变按钮的颜色");
JButton btnRestore=new JButton("还原按钮颜色");
//Graphics gra=new Graphics();
Color color=btnColor.getBackground();
public ComponentEvents ()
{
super("ComponentEvents");
setSize(600,300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
b1.addActionListener(this);
b2.addActionListener(this);
btnColor.addActionListener(this);
btnRestore.addActionListener(this);
JPanel pane=new JPanel();
pane.setLayout(null);
pane.add(b1);
pane.add(b2);
pane.add(btnColor);
pane.add(btnRestore);
setContentPane(pane);
setVisible(true);
}
public void actionPerformed(ActionEvent evt)
{
Object source=evt.getSource();
if(source==b1)
setTitle("dkf");
else if(source==b2)
setTitle("ComponentEvents");
else if (source==btnColor)
{
btnColor.setBackground(Color.orange);
}
else if (source==btnRestore)
{
btnColor.setBackground(color);
}
}
public void paint(Graphics g)
{
b1.setBounds(10,20,150,20);
b2.setBounds(160,20,150,20);
btnColor.setBounds(10,60,150,20);
btnRestore.setBounds(160,60,150,20);
g.drawLine(10,170,500,170);
//repaint();
}
public static void main(String[] args)
{
ComponentEvents comevt= new ComponentEvents();
}
}
我想问下,当程序运行时,窗口有四个按钮与一条直线,但当最小化时,再还原,四个按钮消失.请问大家这是什么问题.
------解决方案--------------------
我给你改了哈，可以了，我觉得不要继承JFrame这个类好些
- Java code
import java.awt.event.*; import javax.swing.*; import java.awt.*; public class ComponentEvents implements ActionListener { JFrame jf = new JFrame(); JButton b1=new JButton("改变框架的主题."); JButton b2=new JButton("还原框架的主题"); JButton btnColor=new JButton("改变按钮的颜色"); JButton btnRestore=new JButton("还原按钮颜色"); //Graphics gra=new Graphics(); Color color=btnColor.getBackground(); public ComponentEvents () { jf.setTitle("ComponentEvents"); jf.setSize(600,300); jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); b1.addActionListener(this); b2.addActionListener(this); btnColor.addActionListener(this); btnRestore.addActionListener(this); b1.setBounds(10,20,150,20); b2.setBounds(160,20,150,20); btnColor.setBounds(10,60,150,20); btnRestore.setBounds(160,60,150,20); JPanel pane=new JPanel(); pane.setLayout(null); pane.add(b1); pane.add(b2); pane.add(btnColor); pane.add(btnRestore); jf.add(pane); jf.setVisible(true); } public void actionPerformed(ActionEvent evt) { Object source=evt.getSource(); if(source==b1) jf.setTitle("dkf"); else if(source==b2) jf.setTitle("ComponentEvents"); else if (source==btnColor) { btnColor.setBackground(Color.orange); } else if (source==btnRestore) { btnColor.setBackground(color); } } // public void paint(Graphics g) // { // b1.setBounds(10,20,150,20); // b2.setBounds(160,20,150,20); // btnColor.setBounds(10,60,150,20); // btnRestore.setBounds(160,60,150,20); // g.drawLine(10,170,500,170); // //repaint(); // } public static void main(String[] args) { ComponentEvents comevt= new ComponentEvents(); } }