Question

JAVA问一个JLabel的问题

package chapter16;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class java16_3 extends JFrame {
private JButton jb1=new JButton("enlarge");
private JButton jb2=new JButton("enshort");
private JButton jb3=new JButton("changespeed");
private JLabel jl1=null;//先定义JLabel类，并不对其进行初始化
private CirclePanel canvas=new CirclePanel();
public static void main(String[] args) {//主函数
JFrame frame=new java16_3();
frame.setTitle("java16_3");
frame.setSize(800,600);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public java16_3()//构造函数
{
JPanel panel=new JPanel();
jl1=new JLabel("speed: "+ canvas.getspeed());
panel.add(jb1);
panel.add(jb2);
panel.add(jb3);
panel.add(jl1);
this.add(canvas,BorderLayout.CENTER);
this.add(panel,BorderLayout.SOUTH);
jb1.addActionListener(new jb1Listener());//new(创建)一个监听类，注册监听
jb2.addActionListener(new jb2Listener());
jb3.addActionListener(new jb3Listener());
}
class jb1Listener implements ActionListener//定义监听类，听过该监听类来调用enlarge()方法
{
public void actionPerformed(ActionEvent e)//当事件发生时，调用该方法
{
canvas.enlarge();//只有用类实例才能调用方法
}
}
class jb2Listener implements ActionListener//定义监听类，听过该监听类来调用enlarge()方法
{
public void actionPerformed(ActionEvent e)//当事件发生时，调用该方法
{
canvas.enshort();
}
}

class jb3Listener implements ActionListener//定义监听类，听过该监听类来调用enlarge()方法
{
public void actionPerformed(ActionEvent e)//当事件发生时，调用该方法
{
canvas.changespeed();
}
}
class CirclePanel extends JPanel//画圆的类
{
private int radius=5;
private int speed=1;
public int getspeed()
{
return speed;
}
public void changespeed()
{
speed++;
repaint();
}
public void enlarge()//增大圆的半径
{
radius=radius+speed;
repaint();//重绘
}
public void enshort()//减小圆的半径
{
if(radius>=0)
{
radius=radius-speed;
repaint();
}
}
protected void paintComponent(Graphics g)//画出圆
{
super.paintComponent(g);
g.drawOval(getWidth()/2-radius,getHeight()/2-radius , 2*radius, 2*radius);
}
}

}
怎么让jl1中的speed数值随着点击changespeed按钮而显示改变之后的速度？

Answer 1

您好，这样的：
public class text
{
JFrame jf;
JButton jb1;
JLabel jl;
JPanel jp1;
JPanel jp2;
JButton jb2;
public static void main(String[] args)
{
text t=new text();
t.go();
}
void go()
{
final ImageIcon image1 = new ImageIcon("1.gif");
final ImageIcon image2 = new ImageIcon("2.gif");
jf=new JFrame("777");
jl = new JLabel(image1);

jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.setSize(300, 300);
jf.setLocation(400, 300);

jp1 = new JPanel();
jp2 = new JPanel();

jb1=new JButton("111");
jb2 =new JButton("222");

jf.getContentPane().add(jp1,BorderLayout.NORTH);
jf.getContentPane().add(jp2,BorderLayout.CENTER);

jp1.add(jb1);
jp2.add(jb2);
jp2.add(jl);

jb1.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
jl.setIcon(image1);
jp2.repaint();
}
});

jb2.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
jl.setIcon(image2);
jp2.repaint();
}
});

jf.setVisible(true);
}
}

Answer 2

楼主，不清楚speed是做什么使用的。

追问

speed是用来改变圆的半径大小的速度，就是按一下圆的半径是很快变大还是慢慢变大

speed是用来改变圆的半径大小的速度，就是按一下圆的半径是很快变大还是慢慢变大

追答

类变量1，原半径
类变量2，定义目标的半径
类变量3，半径的渐变变量

在paint中，半径不断增从原半径、到目标半径