案例1：计算器

1、案例剖析 案例一：计算器所属章节：JAVA的控件教学目的：· 掌握Applet的基本编写 · 掌握字体和颜色的设置· 掌握容器的使用· 掌握布局管理器的使用· 菜单类组件的使用 设计要求：· 设计一个标准型的计算机程序 · 该程序可以通过鼠标依次输入参加计算的数值,不仅可以参加加、减、乘、除等简单的运算,还可以完成sqrt 、%、1/x 等运算. 相关知识· 图形绘制 · Color 类、Math类· 日期时间的格式化案例剖析· 该计算器程序由一个JAVA源文件组成,即Claculat

2、or.java. · Claculator.java 中有3个方法: Claculator(构造方法)、actionPerformed(处理事件方法)、main(主方法) · main(主方法)是程序的入口· 在Claculator方法中主要完成对Claculator类对象的初始代操作,在actionPerformed方汉中实现各个按钮的功能.参考代码/计算器import java.awt.*;import java.lang.*;import javax.swing.*;import javax.swing.event.*;import java.awt.eve

3、nt.*;import java.text.DecimalFormat;public class Calculator implements ActionListener /导入动作监听接口 /设计面板中的单位 JFrame frame; JTextField textAnswer; JPanel panel, panel1, panel2, panel3; JMenuBar mainMenu; JTextField textMemory; JLabel labelMemSpace; /labelMemSpace单纯做摆设，控制面板的形状 JButton buttonBk, buttonCe,

4、 buttonC; JButton button; JButton buttonMC, buttonMR, buttonMS, buttonMAdd; JButton buttonDot, buttonAddAndSub, buttonAdd, buttonSub, buttonMul,buttonDiv, buttonMod; JButton buttonSqrt, buttonDao, buttonEqual; JMenu editMenu, viewMenu, helpMenu; JMenuItem copyItem, pasteItem, tItem, sItem, numberGro

5、up, topHelp, aboutCal; DecimalFormat df; /设置数据输出精度 boolean clickable; /控制当前能否按键 double memoryd; /使用内存中存储的数字 int memoryi; double vard, answerd; /用来保存double型数据的中间值(vard)和最后结果(answerd) short key = -1, prekey = -1; /key用来保存当前进行何种运算,prekey用来保存前次进行何种运算 String copy; /做复制用 JTextArea help; /帮助 JScrollPane sc

6、rollHelp; /构造函数 public Calculator() clickable = true; answerd = 0; frame = new JFrame("计算器"); df = new DecimalFormat("0.#"); /设置数据输出精度(对于double型值) textAnswer = new JTextField(15); textAnswer.setText(""); textAnswer.setEditable(false); textAnswer.setBackground(new Color(

7、255, 255, 255); panel = new JPanel(); frame.getContentPane().add(panel); panel1 = new JPanel(); panel2 = new JPanel(); panel.setLayout(new BorderLayout(); /设计整个面板 mainMenu = new JMenuBar(); editMenu = new JMenu("编辑(E)"); viewMenu = new JMenu("查看(V)"); helpMenu = new JMenu("帮

8、助(H)"); copyItem = new JMenuItem("复制(C) Ctrl+C"); copyItem.addActionListener(this); pasteItem = new JMenuItem("粘贴(V) Ctrl+V"); pasteItem.addActionListener(this); editMenu.add(copyItem); editMenu.add(pasteItem); tItem = new JMenuItem("标准型(T)"); tItem.addActionListen

9、er(this); sItem = new JMenuItem(" 科学型(S)"); sItem.addActionListener(this); numberGroup = new JMenuItem(" 数字分组(I)"); numberGroup.addActionListener(this); viewMenu.add(tItem); viewMenu.add(sItem); viewMenu.add(numberGroup); topHelp = new JMenuItem("帮助主题(H)"); topHelp.addA

10、ctionListener(this); help = new JTextArea(5, 20); scrollHelp = new JScrollPane(help); help.setEditable(false); help.append("执行简单计算n"); help.append("1. 键入计算的第一个数字。n"); help.append("2. 单击“+”执行加、“-”执行减、“*”执行乘或“/”执行除。n"); help.append("3. 键入计算的下一个数字。n"); help.appen

11、d("4. 输入所有剩余的运算符和数字。n"); help.append("5. 单击“=”。n"); aboutCal = new JMenuItem("关于计算器(A)"); aboutCal.addActionListener(this); helpMenu.add(topHelp); helpMenu.add(aboutCal); mainMenu.add(editMenu); mainMenu.add(viewMenu); mainMenu.add(helpMenu); panel.add(mainMenu, BorderL

12、ayout.NORTH); panel.add(textAnswer, BorderLayout.CENTER); panel.add(panel1, BorderLayout.SOUTH); panel1.setLayout(new BorderLayout(); textMemory = new JTextField(3); textMemory.setEditable(false); textMemory.setBackground(new Color(217, 217, 217); labelMemSpace = new JLabel(" "); buttonBk

13、= new JButton("Backspace"); buttonBk.setForeground(new Color(255, 0, 0); buttonCe = new JButton("CE"); buttonCe.setForeground(new Color(255, 0, 0); buttonC = new JButton("C"); buttonC.setForeground(new Color(255, 0, 0); buttonBk.addActionListener(this); buttonCe.addActi

14、onListener(this); buttonC.addActionListener(this); panel1.add(panel2, BorderLayout.NORTH); panel2.setLayout(new FlowLayout(FlowLayout.RIGHT); panel2.add(textMemory); panel2.add(labelMemSpace); panel2.add(buttonBk); panel2.add(buttonCe); panel2.add(buttonC); panel3 = new JPanel(); panel1.add(panel3,

15、BorderLayout.CENTER); button = new JButton10; for (int i = 0; i < button.length; i+) buttoni = new JButton(Integer.toString(i); buttoni.setForeground(new Color(0, 0, 255); buttonMC = new JButton("MC"); buttonMC.setForeground(new Color(255, 0, 0); buttonMR = new JButton("MR");

16、buttonMR.setForeground(new Color(255, 0, 0); buttonMS = new JButton("MS"); buttonMS.setForeground(new Color(255, 0, 0); buttonMAdd = new JButton("M+"); buttonMAdd.setForeground(new Color(255, 0, 0); buttonDot = new JButton("."); buttonDot.setForeground(new Color(0, 0, 2

17、55); buttonAddAndSub = new JButton("+/-"); buttonAddAndSub.setForeground(new Color(0, 0, 255); buttonAdd = new JButton("+"); buttonAdd.setForeground(new Color(255, 0, 0); buttonSub = new JButton("-"); buttonSub.setForeground(new Color(255, 0, 0); buttonMul = new JButton

18、("*"); buttonMul.setForeground(new Color(255, 0, 0); buttonDiv = new JButton("/"); buttonDiv.setForeground(new Color(255, 0, 0); buttonMod = new JButton("%"); buttonMod.setForeground(new Color(0, 0, 255); buttonSqrt = new JButton("sqrt"); buttonSqrt.setForegro

19、und(new Color(0, 0, 255); buttonDao = new JButton("1/x"); buttonDao.setForeground(new Color(0, 0, 255); buttonEqual = new JButton("="); buttonEqual.setForeground(new Color(255, 0, 0); /将所有行为与监听绑定 panel3.setLayout(new GridLayout(4, 6); panel3.add(buttonMC); buttonMC.addActionListe

20、ner(this); panel3.add(button7); button7.addActionListener(this); panel3.add(button8); button8.addActionListener(this); panel3.add(button9); button9.addActionListener(this); panel3.add(buttonDiv); buttonDiv.addActionListener(this); panel3.add(buttonSqrt); buttonSqrt.addActionListener(this); panel3.ad

21、d(buttonMR); buttonMR.addActionListener(this); panel3.add(button4); button4.addActionListener(this); panel3.add(button5); button5.addActionListener(this); panel3.add(button6); button6.addActionListener(this); panel3.add(buttonMul); buttonMul.addActionListener(this); panel3.add(buttonMod); buttonMod.

22、addActionListener(this); panel3.add(buttonMS); buttonMS.addActionListener(this); panel3.add(button1); button1.addActionListener(this); panel3.add(button2); button2.addActionListener(this); panel3.add(button3); button3.addActionListener(this); panel3.add(buttonSub); buttonSub.addActionListener(this);

23、 panel3.add(buttonDao); buttonDao.addActionListener(this); panel3.add(buttonMAdd); buttonMAdd.addActionListener(this); panel3.add(button0); button0.addActionListener(this); panel3.add(buttonAddAndSub); buttonAddAndSub.addActionListener(this); panel3.add(buttonDot); buttonDot.addActionListener(this);

24、 panel3.add(buttonAdd); buttonAdd.addActionListener(this); panel3.add(buttonEqual); buttonEqual.addActionListener(this); frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE); frame.pack(); frame.show(); /设置各个按钮行为 public void actionPerformed(ActionEvent event) boolean sign = false; /判断是否是double型数参与运算，

25、是为true，不是为false Object temp = event.getSource(); try /如果按下数据按钮，将按下的按钮代表的数据插入的当前文本框字符串之后 for (int i = 0; i <= 9; i+) if (temp = buttoni && clickable = true) textAnswer.setText(textAnswer.getText() + Integer.toString(i); /按下'.'按钮时，判断当前文本框内字符串中含不含'.'，如果已含，则不允许再插入'.' i

26、f (temp = buttonDot && clickable = true) boolean isDot = false; if (textAnswer.getText().length() = 0) isDot = true; for (int i = 0; i < textAnswer.getText().length(); i+) if ('.' = textAnswer.getText().charAt(i) isDot = true; break; if (isDot = false) textAnswer.setText(textAnswe

27、r.getText() + "."); if ( (temp = buttonAdd | temp = buttonSub | temp = buttonMul | temp = buttonDiv) && clickable = true) /'+'操作 if (temp = buttonAdd) switch (prekey) case 0: answerd += Double.parseDouble(textAnswer.getText(); break; case 1: answerd -= Double.parseDouble(te

28、xtAnswer.getText(); break; case 2: answerd *= Double.parseDouble(textAnswer.getText(); break; case 3: if (Double.parseDouble(textAnswer.getText() = 0) textAnswer.setText("除数不能为零"); clickable = false; else answerd /= Double.parseDouble(textAnswer.getText(); break; default: answerd = Double.

29、parseDouble(textAnswer.getText(); textAnswer.setText(""); prekey = key = 0; /'-'操作 if (temp = buttonSub) switch (prekey) case 0: answerd += Double.parseDouble(textAnswer.getText(); break; case 1: answerd -= Double.parseDouble(textAnswer.getText(); break; case 2: answerd *= Double.p

30、arseDouble(textAnswer.getText(); break; case 3: if (Double.parseDouble(textAnswer.getText() = 0) textAnswer.setText("除数不能为零"); clickable = false; else answerd /= Double.parseDouble(textAnswer.getText(); break; default: answerd = Double.parseDouble(textAnswer.getText(); textAnswer.setText(&

31、quot;"); prekey = key = 1; /'*'操作 if (temp = buttonMul) switch (prekey) case 0: answerd += Double.parseDouble(textAnswer.getText(); break; case 1: answerd -= Double.parseDouble(textAnswer.getText(); break; case 2: answerd *= Double.parseDouble(textAnswer.getText(); break; case 3: if (Do

32、uble.parseDouble(textAnswer.getText() = 0) textAnswer.setText("除数不能为零"); clickable = false; else answerd /= Double.parseDouble(textAnswer.getText(); break; default: answerd = Double.parseDouble(textAnswer.getText(); textAnswer.setText(""); prekey = key = 2; /'/'操作 if (tem

33、p = buttonDiv) switch (prekey) case 0: answerd += Double.parseDouble(textAnswer.getText(); break; case 1: answerd -= Double.parseDouble(textAnswer.getText(); break; case 2: answerd *= Double.parseDouble(textAnswer.getText(); break; case 3: if (Double.parseDouble(textAnswer.getText() = 0) textAnswer.

34、setText("除数不能为零"); clickable = false; else answerd /= Double.parseDouble(textAnswer.getText(); break; default: answerd = Double.parseDouble(textAnswer.getText(); textAnswer.setText(""); prekey = key = 3; /'='操作 if (temp = buttonEqual && clickable = true) /如果连续按

35、9;=',则进行连续运算 if (prekey = 5) if (key = 0) answerd += vard; textAnswer.setText(df.format(answerd); if (key = 1) answerd -= vard; textAnswer.setText(df.format(answerd); if (key = 2) answerd *= vard; textAnswer.setText(df.format(answerd); if (key = 3) if (Double.parseDouble(textAnswer.getText() = 0

36、) textAnswer.setText("除数不能为零"); clickable = false; else answerd /= vard; textAnswer.setText(df.format(answerd); else vard = Double.parseDouble(textAnswer.getText(); if (key = 0) prekey = -1; answerd += Double.parseDouble(textAnswer.getText(); textAnswer.setText(df.format(answerd); if (key

37、= 1) prekey = -1; answerd -= Double.parseDouble(textAnswer.getText(); textAnswer.setText(df.format(answerd); if (key = 2) prekey = -1; answerd *= Double.parseDouble(textAnswer.getText(); textAnswer.setText(df.format(answerd); if (key = 3) prekey = -1; if (Double.parseDouble(textAnswer.getText() = 0)

38、 textAnswer.setText("除数不能为零"); clickable = false; else answerd /= Double.parseDouble(textAnswer.getText(); textAnswer.setText(df.format(answerd); prekey = 5; /'%'操作，对第二个操作数除以100 if (temp = buttonMod && clickable = true) if (answerd = 0) String s = textAnswer.getText(); text

39、Answer.setText(s); else boolean isDot = false; for (int i = 0; i < textAnswer.getText().length(); i+) if ('.' = textAnswer.getText().charAt(i) isDot = true; break; /如果是double数，除100 if (isDot = true) double dtemp = Double.parseDouble(textAnswer.getText(); dtemp = dtemp / 100.0; textAnswer.

40、setText(Double.toString(dtemp); else /如果是int数但能被100整除，则去掉末尾两个零 if (Integer.parseInt(textAnswer.getText() % 100 = 0) int itemp = Integer.parseInt(textAnswer.getText(); itemp /= 100; textAnswer.setText(Integer.toString(itemp); /如果是int数，但不能被100整除，则按double数处理 else double dtemp = Double.parseDouble(textA

41、nswer.getText(); dtemp = dtemp / 100.0; textAnswer.setText(Double.toString(dtemp); /开根号运算 if (temp = buttonSqrt && clickable = true) String s = textAnswer.getText(); if (s.charAt(0) = '-') textAnswer.setText("负数不能开根号"); clickable = false; else textAnswer.setText(Double.toSt

42、ring(java.lang.Math.sqrt(Double. parseDouble(textAnswer.getText(); /倒数运算 if (temp = buttonDao && clickable = true) if (textAnswer.getText().charAt(0) = '0' && textAnswer.getText().length() = 1) textAnswer.setText("零不能求倒数"); clickable = false; else boolean isDec = tr

43、ue; int i, j, k; String s = Double.toString(1 / Double.parseDouble(textAnswer.getText(); for (i = 0; i < s.length(); i+) if (s.charAt(i) = '.') break; for (j = i + 1; j < s.length(); j+) if (s.charAt(j) != '0') isDec = false; break; if (isDec = true) String stemp = ""

44、 for (k = 0; k < i; k+) stemp += s.charAt(k); textAnswer.setText(stemp); else textAnswer.setText(s); /按下'+/-'按钮时处理 if (temp = buttonAddAndSub && clickable = true) boolean isNumber = true; String s = textAnswer.getText(); for (int i = 0; i < s.length(); i+) if (! (s.charAt(i) &g

45、t;= '0' && s.charAt(i) <= '9' | s.charAt(i) = '.' | s.charAt(i) = '-') isNumber = false; break; if (isNumber = true) /如果当前字符串首字母有'-'号,代表现在是个负数,再按下时,则将首符号去掉 if (s.charAt(0) = '-') textAnswer.setText(""); for (int i = 1; i < s.len

46、gth(); i+) char a = s.charAt(i); textAnswer.setText(textAnswer.getText() + a); /如果当前字符串第一个字符不是符号，则添加一个符号在首字母处 else textAnswer.setText('-' + s); /计算器有关内存操作 /'MC'的操作，将内存清0 if (temp = buttonMC && clickable = true) memoryd = memoryi = 0; textMemory.setText(""); /'MS'的操作，将当前文本框内容保存入内存，显示'M' if (temp = buttonMS && clickable = true) boolean i