一、实验目的
掌握图形用户界面的设计与实现。
二、实验内容
使用图形界面制作一个计算器并实现相应功能。
三、实验步骤
public class firstapp extends Applet implements ActionListener {
private String[] LEFTKEYS = { "7", "8", "9", "4", "5", "6", "1", "2", "3", "0", "+/-", "." };
private String[] RIGHTKEYS = { "/", "sqrt", "ln", "*", "sin", "<-", "-", "cos", "CE", "+", "y^x", "=" };
private Button leftKeys[] = new Button[LEFTKEYS.length];
private Button rightKeys[] = new Button[RIGHTKEYS.length];
private TextField resultText = new TextField("0");
private double resultNum = 0.0;
private String operator = "=";
private boolean startInput = true;
public firstapp() {
init();
}
public void init() {
resultText.setEditable(false);
resultText.setBackground(Color.WHITE);
Panel leftPanel = new Panel();// 左边按钮
leftPanel.setLayout(new GridLayout(4, 3, 3, 3));
for (int i = 0; i < LEFTKEYS.length; i++) {
leftKeys[i] = new Button(LEFTKEYS[i]);
leftPanel.add(leftKeys[i]);
leftKeys[i].setForeground(Color.RED);
}
Panel rightPanel = new Panel();
rightPanel.setLayout(new GridLayout(4, 3, 3, 3));
for (int i = 0; i < RIGHTKEYS.length; i++) {
rightKeys[i] = new Button(RIGHTKEYS[i]);
rightPanel.add(rightKeys[i]);
rightKeys[i].setForeground(Color.blue);
}
this.setLayout(new BorderLayout());
this.add(resultText, BorderLayout.NORTH);
this.add(leftPanel, BorderLayout.WEST);
this.add(rightPanel, BorderLayout.EAST);
for (int i = 0; i < LEFTKEYS.length; i++) {
leftKeys[i].addActionListener(this);
}
for (int i = 0; i < RIGHTKEYS.length; i++) {
rightKeys[i].addActionListener(this);
}
}
public void actionPerformed(ActionEvent e) {
// TODO 自动生成的方法存根
String label = e.getActionCommand();
if (label.equals(RIGHTKEYS[8])) {
// 处理CE
resultText.setText("0");
startInput = true;
} else if (label.equals(RIGHTKEYS[5])) {
// 处理退格
handleBackSpace();
} else if ("0123456789.".indexOf(label) >= 0) {
// 处理数字n
handleNum(label);
} else {
// 处理运算符
handleOperate(label);
}
}
private void handleBackSpace() {
String text = resultText.getText();
int i = text.length();
text = text.substring(0, i - 1);
if (text.length() == 0) {
// 如果文本没有了内容,显示0
resultText.setText("0");
} else {
// 显示新的文本
resultText.setText(text);
}
}
private void handleNum(String key) {
if (startInput) {
if (key.equals(".")) {
resultText.setText(resultText.getText() + ".");
} else {
resultText.setText(key);
}
} else if ((key.equals(".")) && (resultText.getText().indexOf(".") < 0)) {
resultText.setText(resultText.getText() + ".");
} else if (!key.equals(".")) {
resultText.setText(resultText.getText() + key);
}
startInput = false;
}
private void handleOperate(String key) {
if (key.equals(RIGHTKEYS[1]) || key.equals(RIGHTKEYS[2]) || key.equals(RIGHTKEYS[4]) || key.equals(RIGHTKEYS[7])
|| key.equals(LEFTKEYS[10])) {
if (key.equals(RIGHTKEYS[1])) { // 处理sqrt
if (getNumFromText() < 0.0) {
resultText.setText("小于0的数不能开方");
} else {
resultNum = Math.sqrt(getNumFromText());
}
}
if (key.equals(RIGHTKEYS[2])) { // 处理ln
if (getNumFromText() <= 0.0) {
resultText.setText("小于等于0的数不能求对数");
} else {
resultNum = Math.log(getNumFromText());
}
}
if (key.equals(RIGHTKEYS[4])) { // 处理sin
resultNum = Math.sin(getNumFromText());
}
if (key.equals(RIGHTKEYS[7])) { // 处理cos
resultNum = Math.cos(getNumFromText());
}
if (key.equals(LEFTKEYS[10])) { // 处理+/-
resultNum = getNumFromText() * (-1);
}
resultText.setText(String.valueOf(resultNum));
startInput = true;
}
else {
if (operator.equals("/")) {
// 除
if (resultText.getText().equals("0")) {
resultText.setText("除数不能为零");
} else {
resultNum /= getNumFromText();
}
} else if (operator.equals("+")) {
// 加
resultNum += getNumFromText();
} else if (operator.equals("-")) {
// 减
resultNum -= getNumFromText();
} else if (operator.equals("*")) {
// 乘
resultNum *= getNumFromText();
} else if (operator.equals("=")) {
// 赋值
resultNum = getNumFromText();
} else if (operator.equals("y^x")) {
// pow
resultNum = Math.pow(resultNum, getNumFromText());
}
resultText.setText(String.valueOf(resultNum));
operator = key;
startInput = true;
}
}
private double getNumFromText() {
double textDouble;
textDouble = Double.valueOf(resultText.getText()).doubleValue();
return textDouble;
}
public static void main(String args[]) {
firstapp firstapp1 = new firstapp();
firstapp1.setVisible(true);
}
}四、实验总结
本次实验使我学会了如何实现图形用户界面，知道了awt各组件的相关参数、窗口的布局等相关知识。明白了接口的定义及其实现方法，了解了JAVA的事件及处理机制，学会了事件监听者类的使用。现在，我能够写出一些简单的图形用户界面程序了。
