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1、小应用程序Applet设计一、 课题内容和要求内容：设计和编写一个可以用鼠标操作的Applet小应用程序和相应的HTML页面，观察Applet的执行过程，测试程序鼠标用户交互操作的效果。要求：要求学生能在学习和理解课堂学习内容中JAVA小应用程序的基础上，通过实验，培养学生将JAVA小应用程序相关知识点（包括JAVA Applet和低级事件处理模型）有机结合，设计基于WEB浏览器的小应用程序的能力。二、设计思路分析class App:一个Java Applet计算器的主类public void init():完成初始化appletpublic boolean action():实现事件处理的方
2、法public void doOperator():运算及运算结果输出操作public void doForeScreen():数字和小数点输出到文本框操作public void doClear():清空操作三、概要设计public class App extends Applet TextField tfAnswer;Button b0, b1, b2, b3, b4, b5, b6, b7, b8, b9;Button bPoint, bEqual, bPlus, bMinus, bClear, bMulti, bDivision;String OperatorCurrent, Opera
3、torPre;String ForeScreen, BackScreen;boolean isFloat = false;public void init();public boolean action(Event e, Object o);public void doOperator()public void doForeScreen(String s);public void doClear();事件处理:运算及运算结果输出:四、详细设计Java代码：import java.awt.*;import java.applet.*;public class App extends Applet
4、 TextField tfAnswer;/ 定义变量Button b0, b1, b2, b3, b4, b5, b6, b7, b8, b9;Button bPoint, bEqual, bPlus, bMinus, bClear, bMulti, bDivision;String OperatorCurrent, OperatorPre;String ForeScreen, BackScreen;boolean isFloat = false;public void init() / 初始化OperatorCurrent = new String();OperatorPre = new S
5、tring();ForeScreen = new String(0);/ 保证输入字符串不为空防止计算错误BackScreen = new String();setBackground(Color.gray);setLayout(null);/ 设为空布局便于自定义组件位置tfAnswer = new TextField();/ 设置文本框样式tfAnswer.setBounds(20, 20, 175, 40);tfAnswer.setFont(new Font(BackScreen, Font.BOLD, 28);add(tfAnswer);tfAnswer.setText(ForeScr
6、een);bClear = new Button(C);/ 设置按钮样式bClear.setBounds(20, 70, 40, 40);add(bClear);bDivision = new Button(/);bDivision.setBackground(Color.green);bDivision.setBounds(65, 70, 40, 40);add(bDivision);bMulti = new Button(*);bMulti.setBackground(Color.green);bMulti.setBounds(110, 70, 40, 40);add(bMulti);bM
7、inus = new Button(-);bMinus.setBackground(Color.green);bMinus.setBounds(155, 70, 40, 40);add(bMinus);b7 = new Button(7);b7.setBounds(20, 115, 40, 40);b7.setBackground(Color.orange);add(b7);b8 = new Button(8);b8.setBackground(Color.orange);b8.setBounds(65, 115, 40, 40);add(b8);b9 = new Button(9);b9.s
8、etBackground(Color.orange);b9.setBounds(110, 115, 40, 40);add(b9);bPlus = new Button(+);bPlus.setBackground(Color.green);bPlus.setBounds(155, 115, 40, 85);add(bPlus);b4 = new Button(4);b4.setBackground(Color.orange);b4.setBounds(20, 160, 40, 40);add(b4);b5 = new Button(5);b5.setBackground(Color.oran
9、ge);b5.setBounds(65, 160, 40, 40);add(b5);b6 = new Button(6);b6.setBackground(Color.orange);b6.setBounds(110, 160, 40, 40);add(b6);b1 = new Button(1);b1.setBackground(Color.orange);b1.setBounds(20, 205, 40, 40);add(b1);b2 = new Button(2);b2.setBackground(Color.orange);b2.setBounds(65, 205, 40, 40);a
10、dd(b2);b3 = new Button(3);b3.setBackground(Color.orange);b3.setBounds(110, 205, 40, 40);add(b3);bEqual = new Button(=);bEqual.setBackground(Color.green);bEqual.setBounds(155, 205, 40, 85);add(bEqual);b0 = new Button(0);b0.setBackground(Color.orange);b0.setBounds(20, 250, 85, 40);add(b0);bPoint = new
11、 Button(.);bPoint.setBackground(Color.orange);bPoint.setBounds(110, 250, 40, 40);add(bPoint);public boolean action(Event e, Object o) / 实现事件处理的方法String s = new String();if (e.target = b0) | (e.target = b1) | (e.target = b2)| (e.target = b3) | (e.target = b4) | (e.target = b5)| (e.target = b6) | (e.t
12、arget = b7) | (e.target = b8)| (e.target = b9) / 获取数字按钮数据并在控制台和文本框输出if (e.target != bPoint) / 获取数字s = (String) o;doForeScreen(s);if (e.target = bPoint) & !ForeScreen.contains(.) / 保证原数不含小数点的情况下获取小数点并在控制台和文本框输出s = (String) o;if (ForeScreen.equals()/ 原来没有输入数据则用0.doForeScreen(0.); else/ 原来有输入数据则用.doFor
13、eScreen(s);if (e.target = bClear) / 清除按钮进行清除操作doClear();if (e.target = bMulti) | (e.target = bDivision)| (e.target = bPlus) | (e.target = bMinus)| (e.target = bEqual) / 加减乘除等于按钮获取运算操作符并进行运算操作if (ForeScreen != ) / 重新输入数字进行运算操作OperatorCurrent = (String) o);doOperator(); else / 没有重新输入数字则作为上一运算符-保证不输入连续
14、的同一运算符OperatorPre = (String) o);return true;public void doOperator() / 运算及运算结果输出操作double dFore, dBack;Double d;if (OperatorPre.equals() / 上一运算符没有则直接输出BackScreen = ForeScreen;/ 输入的数据转入后台并清空，用后台输出它ForeScreen = ;tfAnswer.setText(BackScreen);repaint(); else / 上一运算符存在则运算后输出dFore = (new Double(ForeScreen).doubleValue();dB
