J2ME计算器源码（高层界面）
/** To change this template, choose Tools | Templates
* and open the template in the editor.
*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
/**
* @author Administrator
*/
public class CalculatorMIDlet extends MIDlet implements CommandListener{
private final Command exitCommand = new Command("退出", Command.EXIT, 2);
private final Command calcCommand = new Command("计算", Command.SCREEN, 1);
/** 接收第一个参数. */
private final TextField arg1 = new TextField("第一个参数", "", 20, TextField.DECIMAL);
/** 接收第二个参数*/
private final TextField arg2 = new TextField("第二个参数", "", 20, TextField.DECIMAL);
/** 显示结果*/
private final TextField ret = new TextField("结果", "", 20, TextField.UNEDITABLE);
/** 运算符的下拉列表框 */
private final ChoiceGroup operator = new ChoiceGroup("运算符", ChoiceGroup.POPUP,
new String[] {"加", "减", "乘", "除"}, null);
/** 计算错误警告*/
private final Alert alert = new Alert("错误", "", null, AlertType.ERROR);
/** 首次运行标志 */
private boolean first= false;
protected void startApp() {
if (first) {
return;
}
Form myForm= new Form("计算器");
myForm.append(arg1);
myForm.append(operator);
myForm.append(arg2);
myForm.append(ret);
myForm.addCommand(calcCommand);
myForm.addCommand(exitCommand);
myForm.setCommandListener(this);
Display.getDisplay(this).setCurrent(myForm);
first = true;
}
protected void destroyApp(boolean unconditional) {}
protected void pauseApp() {}
public void commandAction(Command c, Displayable d) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
return;
}
double result = 0.0;
if (c == calcCommand) {
try {
double d1 = str2double(arg1);
double d2 = str2double (arg2);
switch (operator.getSelectedIndex()) {
case 0: result = d1 + d2; break;
case 1: result = d1 - d2; break;
case 2: result = d1 * d2; break;
case 3: result = d1 / d2; break;
default:
}
} catch (NumberFormatException e) {
return;
} catch (ArithmeticException e) {
alert.setString("除数为零");
Display.getDisplay(this).setCurrent(alert);
return;
}
String str = Double.toString(result);
ret.setString(str);
}
}
private double str2double(TextField t)
throws NumberFormatException {
String s = t.getString();
if (s.length() == 0) {
alert.setString("No Argument");
Display.getDisplay(this).setCurrent(alert);
}
double n = 0.0;
try {
n = Double.parseDouble(s);
} catch (NumberFormatException e) {
alert.setString("操作数超过取值范围");
Display.getDisplay(this).setCurrent(alert);
}
return n;
}
}
