编写简单计算器

1、 今天闲着没事，用java写了一个简单计算器，能实现简单的数据计算。语言：java开发环境：eclipse（因为是按自己的想法写的，所以有些不尽人意的地方请谅解，希望对初学java者有些许帮助，有不好理解的地方，我尽量注释，有不理解的可以在百度HI我） 事先一定要安装好JDK，可以在下载，配置好环境变量，再安装好eclipse，也可以在网上下载到，具体自己去找；然后打开eclipse建立一个工程，取名随便，我这里取名Calculator；然后在建立好的工程里面新建两个包，报名也自己取，尽量易懂，容易让人理解；我这里建立了两个包，Client和UI，等下在Client里面放的是主函数，UI里面放

2、的是界面文件和控制器；好了下面开始写代码；一、 先写界面代码： 在UI包里面新建一个Class文件，取名自己想，这里我写的是CalculatorFramepackage ui;import java.awt.Color;import java.awt.Font;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing

3、.JOptionPane;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.JTextArea;import javax.swing.border.TitledBorder;public class CalculatorFrame extends JFrame private static final long serialVersionUID = 1L;public String opt;public String str;private JTextArea show;private Cli

4、entContext clientContext;/引用控制器对象 /*因为调用了控制器里面的方法，所以要对控制器的对象进行赋值，否则运行会出现空指针异常*/public void setClientContext(ClientContext clientContext) this.clientContext = clientContext;public CalculatorFrame() init();private void init() setTitle(" Simple Calculator");setBounds(533, 184, 300, 400);setCo

5、ntentPane(creatContentPane();private JPanel creatContentPane() JPanel p = new JPanel(new GridLayout(4, 1);/* 在面板里面添加4个面板*/p.add(showPane();/显示屏p.add(btnPane1();/下面三个都是按钮p.add(btnPane2();p.add(btnPane3();return p;/*实现各个面板*/private JScrollPane showPane() JScrollPane p = new JScrollPane();p.setBorder(n

6、ew TitledBorder("Display:");show = new JTextArea();show.setFont(new Font("",Font.PLAIN,25);show.setForeground(Color.RED);show.setLineWrap(true);show.setEditable(false);p.getViewport().add(show);return p;private JPanel btnPane1() JPanel p = new JPanel(new GridLayout(2, 4);JButton

7、add = new JButton("+");JButton jian = new JButton("-");JButton cheng = new JButton("*");JButton chu = new JButton("/");JButton one = new JButton("1");JButton two = new JButton("2");JButton three = new JButton("3");JButton anser =

8、new JButton("=");p.add(add);p.add(jian);p.add(cheng);p.add(chu);p.add(one);p.add(two);p.add(three);p.add(anser);/*用内部类实现按钮监视器，后面的都是这样*/one.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent arg0) String number = show.getText() + String.valueOf(1);/按了数字“1

9、”按/钮后，操作显示屏,既更新一下显示屏clientContext.setNumber(number);/调用控制器里面的方法);two.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent arg0) String number = show.getText() + String.valueOf(2);clientContext.setNumber(number););three.addActionListener(new ActionListener() Override

10、public void actionPerformed(ActionEvent e) / TODO Auto-generated method stubString number = show.getText() + String.valueOf(3);clientContext.setNumber(number););add.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent arg0) opt = "+"clientContext.setOpt(op

11、t););jian.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubopt = "-"clientContext.setOpt(opt););cheng.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated me

12、thod stubopt = "*"clientContext.setOpt(opt););chu.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubopt = "/"clientContext.setOpt(opt););anser.addActionListener(new ActionListener() Overridepublic void actio

13、nPerformed(ActionEvent arg0) str = "="clientContext.setAnswer(str););return p;private JPanel btnPane2() JPanel p = new JPanel(new GridLayout(2, 4);JButton four = new JButton("4");JButton five = new JButton("5");JButton six = new JButton("6");JButton pi = new J

14、Button("PI");JButton seven = new JButton("7");JButton eight = new JButton("8");JButton nine = new JButton("9");JButton com = new JButton(".");p.add(four);p.add(five);p.add(six);p.add(pi);p.add(seven);p.add(eight);p.add(nine);p.add(com);four.addAction

15、Listener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubString number = show.getText() + String.valueOf(4);clientContext.setNumber(number););five.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO

16、 Auto-generated method stubString number = show.getText() + String.valueOf(5);clientContext.setNumber(number););six.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubString number = show.getText() + String.valueOf(6);clientCont

17、ext.setNumber(number););seven.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubString number = show.getText() + String.valueOf(7);clientContext.setNumber(number););eight.addActionListener(new ActionListener() Overridepublic vo

18、id actionPerformed(ActionEvent e) / TODO Auto-generated method stubString number = show.getText() + String.valueOf(8);clientContext.setNumber(number););nine.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubString number = show

19、.getText() + String.valueOf(9);clientContext.setNumber(number););com.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubsetShow(show.getText() + "."););pi.addActionListener(new ActionListener() Overridepublic void acti

20、onPerformed(ActionEvent e) / TODO Auto-generated method stubsetShow(String.valueOf(Math.PI););return p;private JPanel btnPane3() JPanel p = new JPanel(new GridLayout(2, 4);JButton zero = new JButton("0");JButton sqrt = new JButton("");JButton guiling = new JButton("C");

21、final JButton help = new JButton("Help");p.add(zero);p.add(sqrt);p.add(guiling);p.add(help);help.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubJOptionPane.showMessageDialog(help, "注意：假如第二运算数为空的话，这里将默认为0.0！&qu

22、ot;););guiling.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubclientContext.setMc(););zero.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubString num

23、ber = show.getText() + String.valueOf(0);clientContext.setNumber(number););sqrt.addActionListener(new ActionListener() Overridepublic void actionPerformed(ActionEvent e) / TODO Auto-generated method stubsetShow("" + Math.sqrt(getShow(););return p;/*更新计算器的显示屏*/public void setShow(String str

24、) show.setText(str);/*获取当前显示屏里面的数据*/public Double getShow() String str = show.getText();if (str.equals("") str = "0.0"return Double.valueOf(str);/*获取当前选择的运算符：比如加或减或乘或除*/public String getOpt() return this.opt;二、 写控制器代码在UI包建立一个Class，我取名ClientContextpackage ui;import java.util.Array

25、List;import java.util.List;import javax.swing.JOptionPane;public class ClientContext private CalculatorFrame calculatorFrame;private Double first = 0.0;private Double next = 0.0;public void setCalculatorFrame(CalculatorFrame calculatorFrame) this.calculatorFrame = calculatorFrame;double sum = 0;publ

26、ic void setNumber(String str) calculatorFrame.setShow(str);public void setOpt(String opt) first = calculatorFrame.getShow();calculatorFrame.setShow("");public void setAnswer(String str) /按了“=”后，对数据按运算符进行计算next = calculatorFrame.getShow();/ calculatorFrame.setShow(str);/switch(str)/if (calc

27、ulatorFrame.getOpt() = "+") double answer = first + next;calculatorFrame.setShow(String.valueOf(answer); else if (calculatorFrame.getOpt() = "-") double answer = first - next;calculatorFrame.setShow(String.valueOf(answer); else if (calculatorFrame.getOpt() = "*") double