JAVASE—GUI 之简单计算器的实现

图形用户界面是使用图形的方式借助窗口、文本行、按钮

实现代码：

package mypackage;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class caculator extends JFrame{
	
	
	//用来显示数值
	JLabel show = new JLabel();
	JPanel main=new JPanel();
	JPanel numPanel= new JPanel();
	boolean start;//判断是否重新开始
	int count;//小数点出现次数
	double result;//结果接收结果
	String comd;//接收符号

	public static void main(String[] args) {
		new caculator();
	}
	public caculator(){
		init();
	}
	//布局的方法
	private void init(){
		//给窗体的大小
		this.setSize(500,300);
		//窗体可见
		this.setBackground(java.awt.Color.lightGray);
		this.setVisible(true);
		//让窗体居中的方法
		this.setLocationRelativeTo(null);
		//设置计算器点击退出则程序关闭
		this.setDefaultCloseOperation(EXIT_ON_CLOSE);
		//设置标题
		this.setTitle("Lzz的第一个计算器");
		//给显示框设置默认值0
		show.setText("0");
		//默认开始
		start=true;
		//默认小数点出现次数
		count=0;
		//默认为等
		comd="=";
		//给按钮面板设置布局
		numPanel.setLayout(new GridLayout(5,4));
		
		//准备监听对象
		Actionl actionl=new Actionl();
		Action2 action2=new Action2();
		Action3 action3=new Action3();
		//添加按钮
		this.addButton("Off", action3);
		this.addButton("TIME", action3);
		this.addButton("BREAKSPACE", action3);
		this.addButton("C", action3);
		this.addButton("7", actionl);
		this.addButton("8", actionl);
		this.addButton("9", actionl);
		this.addButton("+", action2);
		this.addButton("4", actionl);
		this.addButton("5", actionl);
		this.addButton("6", actionl);
		this.addButton("-", action2);
		this.addButton("1", actionl);
		this.addButton("2", actionl);
		this.addButton("3", actionl);
		this.addButton("*", action2);
		this.addButton(".", actionl);
		this.addButton("0", actionl);
		this.addButton("=", action2);
		this.addButton("/", action2);
		//给主面版设为边框布局
		main.setLayout(new BorderLayout());
		//让显示框位于主面版北方
		main.add(show ,"North");
		main.add(numPanel);
		this.add(main);
	
	} 
	//添加按钮并给给设置监听按钮的方法
	public void addButton(String num,ActionListener al) {
		JButton button=new JButton(num);
		button.addActionListener(al);
		numPanel.add(button);
	}
	//数字键的监听方法
	class Actionl implements ActionListener{
		
		public void actionPerformed(ActionEvent e) {
			// 监听者监听到之后要做的事
			String input = e.getActionCommand();
			if(show.getText().equals("0")){
				start=true;
			}
			if(start){
				count=0;//小数点归0重新开始
				show.setText("");
				start=false;
			}
			if(input.equals(".")){
				if(count==0){
					show.setText(show.getText()+input);
				}else{
					show.setText(show.getText()+"");
				}
				count++;
			}
			if(!input.equals(".")){
				show.setText(show.getText()+input);
			}
		}
		
	}
	
	//符号键的监听方法
		class Action2 implements ActionListener{

			
			public void actionPerformed(ActionEvent e) {
				String input=e.getActionCommand();
				if(start){
					comd=input;
				}else{
					if(comd.equals("+")){
						//将String类型的数据转换成double类型的数字
						result += Double.parseDouble(show.getText());
					}
					else if(comd.equals("-")){
						//将String类型的数据转换成double类型的数字
						result -= Double.parseDouble(show.getText());
					}
					else if(comd.equals("*")){
						//将String类型的数据转换成double类型的数字
						result *= Double.parseDouble(show.getText());
					}
					else if(comd.equals("/")){
						//将String类型的数据转换成double类型的数字
						result /= Double.parseDouble(show.getText());
					}else{
						result = Double.parseDouble(show.getText());
					}
				}
					 show.setText(result+"");
					comd=input;
					start=true;
				}
			}
		
	//功能键的监听方法 
		class Action3 implements ActionListener{
			
			public void actionPerformed(ActionEvent e) {
				String input=e.getActionCommand();
				if(input.equals("TIME")){
					show.setText(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
					start=true;
				}
				if(input.equals("C")){
					show.setText("0");
				}
				if(input.equals("Off")){
					show.setText(""); 
					start =true;
				}
				if(input.equals("BREAKSPACE")){
					if(show.getText().length()>1){
						show.setText(show.getText().substring(0,show.getText().length()-1));//截取之前的
					}else{
						show.setText("0");
					}
				}
			}
			
		}
}