countercanvas.java

用J2ME开发的一个实用软件——计算器。实现了windows系统自带计算器的基本计算功能

import javax.microedition.lcdui.*;

//主程序
public class CounterCanvas extends Canvas {
	// 按钮选中图片
	Image igButton0;
	// 按钮按下图片
	Image igButton1;
	// 屏显数字图片
	Image igNumber;
	// 错误提示图片
	Image igs1;
	Image igs2;
	Image igs3;
	// 界面背景图片（包括初始按键、标题和说明、退出按钮）
	Image igui0;
	// 显示框图片
	Image igui1;
	// 说明图片
	Image igui2;
	// 字串存储器（顺序为：第一个运算数、第一个运算符号、第二个运算数、计算结果、屏显）
	String[] strMemorizer = new String[5];
	// 主按键索引号，初始为20，显示为按钮非选中状态
	int index = 20;
	// 数字键名与对应的索引号数组
	int[] indexArray = { 16, 12, 13, 14, 8, 9, 10, 4, 5, 6 };
	String[] strNumber = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
	// 运算符键索引号数组与对应的字符数组
	int[] indexFh = { 19, 15, 11, 7 };
	char[] fh = { '+', '-', '*', '/' };
	Graphics g;
	// 变量、刷屏标签、前一按键索引记忆器
	int i, j, lable, n;
	// 临时字串变量(记住：用后要清空)
	String tmp = "";
	// 获取上次按键索引号存储数组
	int[] aheadKeycode = { 20, 20 };

	// 构造方法中引入所需图片
	public CounterCanvas() {
		try {
			igui0 = Image.createImage("/ui0.png");
			igui1 = Image.createImage("/ui1.png");
			igui2 = Image.createImage("/ui2.png");
			igNumber = Image.createImage("/number.png");
			igs1 = Image.createImage("/s1.png");
			igs2 = Image.createImage("/s2.png");
			igs3 = Image.createImage("/s3.png");
			igButton0 = Image.createImage("/button.png");
			igButton1 = Image.createImage("/button0.png");
		} catch (Exception e) {
		}
	}

	// 刷屏
	protected void paint(Graphics g) {
		// 画界面、底层背景
		g.drawImage(igui0, 0, 0, Graphics.TOP | Graphics.LEFT);
		// 画输出立体框(等同于屏显清空)
		cls(g);
		// 按键刷屏
		switch (lable) {
		// 按键选中刷屏
		case 0:
			for (i = 0; i < 20; i++) {
				if (i == index) {
					g.setClip(12 + i % 4 * 57, 84 + i / 4 * 35, 45, 31);
					g.drawImage(igButton0, 12 + i % 4 * 57, 84 + i / 4 * 35 - i
							* 31, Graphics.TOP | Graphics.LEFT);
					g.setClip(0, 0, this.getWidth(), this.getHeight());
					drawScreen(strMemorizer[4], g);
				}
			}
			break;
		// 按键确认刷屏
		case 1:
			for (i = 0; i < 20; i++) {
				if (i == index) {
					g.setClip(12 + i % 4 * 57, 84 + i / 4 * 35, 45, 31);
					g.drawImage(igButton1, 12 + i % 4 * 57, 84 + i / 4 * 35 - i
							* 31, Graphics.TOP | Graphics.LEFT);
					g.setClip(0, 0, this.getWidth(), this.getHeight());
					drawScreen(strMemorizer[4], g);
				}
			}
			break;
		case 2:
			g.drawImage(igui2, 0, 0, Graphics.TOP | Graphics.LEFT);
			break;
		}
		if (lable != 2) {
			drawScreen(strMemorizer[4], g);
		}
	}

	// 手机按键按下，计算器按键被选中（触发）
	public void keyPressed(int keyCode) {
		int action = this.getGameAction(keyCode);
		// 手机键盘按键镜像
		if (keyCode == 48) { // 0键
			index = 16;
			action = FIRE;
		}
		if (keyCode == 49) { // 1键
			index = 12;
			action = FIRE;
		}
		if (keyCode == 50) { // 2键
			index = 13;
			action = FIRE;
		}
		if (keyCode == 51) { // 3键
			index = 14;
			action = FIRE;
		}
		if (keyCode == 52) { // 4键
			index = 8;
			action = FIRE;
		}
		if (keyCode == 53) { // 5键
			index = 9;
			action = FIRE;
		}
		if (keyCode == 54) { // 6键
			index = 10;
			action = FIRE;
		}
		if (keyCode == 55) { // 7键
			index = 4;
			action = FIRE;
		}
		if (keyCode == 56) { // 8键
			index = 5;
			action = FIRE;
		}
		if (keyCode == 57) { // 9键
			index = 6;
			action = FIRE;
		}
		if (keyCode == -8) { // clear键改成镜像到撤消键和清零键
			if (index == 1) {
				index = 2;
			} else if (index == 2) {
				index = 17;
			} else {
				index = 1;
			}
		}
		if (keyCode == 42) { // 用*键切换运算符号
			if (index == 19) {
				index = 15;
			} else if (index == 15) {
				index = 11;
			} else if (index == 11) {
				index = 7;
			} else if (index == 7) {
				index = 3;
			} else {
				index = 19;
			}
		}
		// 按键触发
		switch (action) {
		case UP: // 上移选择框
			if (index == 20) {
				index = 9;
				break;
			}
			if (index / 4 > 0) {
				index -= 4;
			}
			break;
		case DOWN: // 下移选择框
			if (index == 20) {
				index = 9;
				break;
			}
			if (index / 4 < 4) {
				index += 4;
			}
			break;
		case LEFT: // 左移选择框
			if (index == 20) {
				index = 9;
				break;
			}
			if (index % 4 > 0) {
				index--;
			}
			break;
		case RIGHT: // 右移选择框
			if (index == 20) {
				index = 9;
				break;
			}
			if (index % 4 < 3) {
				index++;
			}
			break;
		case KEY_POUND: // 返回上一界面（用在从说明界面返回）
			lable = 0;
			break;
		case FIRE:
			// 计算器按下的前一键的索引号记忆器，在此初始化后传递给其它功能键用，也为按键切换做准备(否则会出现切换停顿)
			n = anteriorIndex();
			if (index == 20) {
				index = 9;
				break;
			}
			switch (index) {
			case 0: // 向前消除键
				backSpace();
				break;
			case 1: // 取消键
				cancel();
				break;
			case 2: // 清零键
				clsZero();
				break;
			case 3: // 等号键
				amount();
				break;
			case 4: // 数字键7
			case 5: // 数字键8
			case 6: // 数字键9
			case 8: // 数字键4
			case 9: // 数字键5
			case 10: // 数字键6
			case 12: // 数字键1
			case 13: // 数字键2
			case 14: // 数字键3
			case 16: // 数字键0
				getNumber();
				break;
			case 7: // 除号键
			case 11: // 乘号键
			case 15: // 减号键
			case 19: // 加号键
				getOperator();
				break;
			case 17: // 取反键
				sign();
				break;
			case 18: // 小数点未定义
				break;
			}
			lable = 1;
			repaint();
			return;
		}
		lable = 0;
		if (keyCode == -7) { // 右软键查看说明
			lable = 2;
		}
		if (keyCode == -6) { // 左软键退出
			CounterMidlet.quitApp();
		}
		repaint();
	}

	// 运算功能
	public String operation(String s) {
		tmp = "";
		for (i = 0; i < s.length(); i++) {
			if (s.charAt(i) == '+') {
				tmp = String.valueOf(Integer.parseInt(s.substring(0, i))
						+ Integer.parseInt(s.substring(i + 1, s.length())));
				break;
			}
			if (s.charAt(i) == '-') {
				if (i == 0) {
					continue;
				}
				tmp = String.valueOf(Integer.parseInt(s.substring(0, i))
						- Integer.parseInt(s.substring(i + 1, s.length())));
				break;
			}
			if (s.charAt(i) == '*') {
				tmp = String.valueOf(Integer.parseInt(s.substring(0, i))
						* Integer.parseInt(s.substring(i + 1, s.length())));
				break;
			}
			if (s.charAt(i) == '/') {
				if (s.equals("0/0")) {
					tmp = "函数无意义!";
					return tmp;
				}
				if (s.endsWith("/0")) {
					tmp = "零不能为除数!";
					return tmp;
				}
				tmp = String.valueOf(Integer.parseInt(s.substring(0, i))
						/ Integer.parseInt(s.substring(i + 1, s.length())));
				break;
			}