菜单栏 JMenubar, 菜单JMenu 菜单项:JMenuItem,菜单栏位于窗口的顶部,菜单放置在菜单栏上,菜单下拉可以看到子菜单。
package com.util.ljc;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class Meau extends JFrame implements ActionListener {
JMenuItem m1,m2,m3,m4,m5;
JTextField jt1,jt2,jt3;
Meau(){
this.setSize(250, 300);
JMenuBar mb=new JMenuBar();//菜单栏
JMenu jm=new JMenu("运算");//菜单
m1=new JMenuItem("加");//创建菜单项
m3=new JMenuItem("减");//创建菜单项
m4=new JMenuItem("乘");//创建菜单项
m5=new JMenuItem("除");//创建菜单项
jm.add(m1);
jm.add(m3);jm.add(m4);jm.add(m5);
JMenu jm2=new JMenu("程序");
m2=new JMenuItem("终止");//创建菜单项
jm2.add(m2);
// jm.remove(mil2);//删除指定的菜单项
mb.add(jm);
mb.add(jm2);
m1.addActionListener(this);
m2.addActionListener(this);
m3.addActionListener(this);
m4.addActionListener(this);
m5.addActionListener(this);
jt1=new JTextField(10);
jt2=new JTextField(10);
jt3=new JTextField(10);
JPanel jp=new JPanel(new GridLayout(3,2));
jp.add(new JLabel("数值一:"));
jp.add(jt1);
jp.add(new JLabel("数值二:"));
jp.add(jt2);
jp.add(new JLabel("运算结果:"));
jp.add(jt3);
add(jp);
this.setJMenuBar(mb);//设置菜单栏
}
public void actionPerformed(ActionEvent e){
if(e.getSource()== m2){
System.exit(0);
}else{
Double num1=new Double(jt1.getText());
Double num2=new Double(jt2.getText());
Double num3= (double) 0;
if(e.getSource()==m1){
num3=num1+num2;
}
else if(e.getSource()==m3){
num3=num1-num2;
}
else if(e.getSource()==m4){
num3=num1*num2;
}
else if(e.getSource()==m5){
num3=num1/num2;
}
jt3.setText(new Double(num3).toString());
}
}
}
package com.util.ljc;
import javax.swing.JFrame;
public class test {
public static void main(String[] args) {
// TODO Auto-generated method stub
Meau m=new Meau();
m.setTitle("四则运算");
m.setSize(250, 180);
m.setLocation(350, 250);
m.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
m.setVisible(true);
}
}
运行效果: