J2ME初学者小游戏

package src; import javax.microedition.lcdui.*; import javax.microedition.lcdui.game.*; import java.util.*; import java.io.*; public class UFOCanvas extends GameCanvas implements Runnable { private Display display; private boolean sleeping; private long frameDelay; private Random rand; private Sprite ufoSprite; private int ufoXSpeed, ufoYSpeed; private Sprite[] roidSprite = new Sprite[5];//精灵数组 private long gametime; private long gametimeoffset; /**游戏暂停变量*/ public boolean isPaused = false; String pauseStr = "暂停"; String continueStr = "继续"; /**游戏结束变量*/ boolean gameOver = false; int width; int height; public UFOCanvas(Display d) { super(false); width = getWidth(); height = getHeight(); display = d; gametime = 0; // Set the frame rate (30 fps) frameDelay = 33; } public void start() { // Set the canvas as the current screen display.setCurrent(this); // Initialize the random number generator rand = new Random(); this.gametimeoffset = System.currentTimeMillis(); // Initialize the UFO and roids sprites ufoXSpeed = ufoYSpeed = 0; try { ufoSprite = new Sprite(Image.createImage("/Saucer.png")); ufoSprite.setPosition((getWidth() - ufoSprite.getWidth()) / 2, (getHeight() - ufoSprite.getHeight()) / 2);//初始化了飞碟的位置 Image img = Image.createImage("/Roid.png");//初始化三个小行星精灵 roidSprite[0] = new Sprite(img, 42, 35); roidSprite[1] = new Sprite(img, 42, 35); roidSprite[2] = new Sprite(img, 42, 35); roidSprite[3] = new Sprite(img, 42, 35); roidSprite[4] = new Sprite(img, 42, 35); //没有设定特定的初始位置，使用的是缺省值（0，0） } catch (IOException e) { System.err.println("Failed loading images!"); } // Start the animation thread sleeping = false; Thread t = new Thread(this); t.start(); } public void stop() { // Stop the animation sleeping = true; } public void run() { Graphics g = getGraphics(); Font f = Font.getFont(Font.FACE_PROPORTIONAL, Font.STYLE_PLAIN, Font.SIZE_LARGE); g.setFont(f); // The main game loop while (!sleeping) { update(); this.gametime = ((System.currentTimeMillis() - gametimeoffset) / 1000); draw(g); try { Thread.sleep(frameDelay); } catch (InterruptedException ie) { } } } private void update() { int keyState = getKeyStates(); if ((keyState & FIRE_PRESSED) != 0) { //右软键，暂停控制 isPaused = !isPaused; } if (!isPaused) { // Process user input to control the UFO speed //检查四个方向键和并以此来改变飞碟的速度 if ((keyState & LEFT_PRESSED) != 0) { ufoXSpeed--; } else if ((keyState & RIGHT_PRESSED) != 0) { ufoXSpeed++; } if ((keyState & UP_PRESSED) != 0) { ufoYSpeed--; } else if ((keyState & DOWN_PRESSED) != 0) { ufoYSpeed++; } ufoXSpeed = Math.min(Math.max(ufoXSpeed, -8), 8);//飞碟的速度是在-8到+8之间随机产生的 ufoYSpeed = Math.min(Math.max(ufoYSpeed, -8), 8); // Move the UFO sprite ufoSprite.move(ufoXSpeed, ufoYSpeed);//移动飞碟 checkBounds(ufoSprite);//检查飞碟的边界 // 更新小行星精灵的循环 for (int i = 0; i < 5; i++) { // Move the roid sprites roidSprite[i].move(i + 1, 1 - i); checkBounds(roidSprite[i]); // 每个小行星都有自己独特的动画帧方向，第二个小行星与第一个和第三个小行星的方向相反 if (i == 1) { roidSprite[i].prevFrame(); } else { roidSprite[i].nextFrame(); } //检测到小行星与飞碟的冲突 if (ufoSprite.collidesWith(roidSprite[i], true)) { // 放出报警音效 AlertType.ERROR.playSound(display); // 重新设置飞碟精灵的位置和速度，回到屏幕中间并且速度设置为0 ufoSprite.setPosition((getWidth() - ufoSprite.getWidth()) / 2, (getHeight() - ufoSprite.getHeight()) / 2); ufoXSpeed = ufoYSpeed = 0; for (int j = 0; j < 5; j++) { roidSprite[j].setPosition(0, 0); }//小行星精灵也要归位 this.gametime = 0; this.gametimeoffset = System.currentTimeMillis(); // 到此说明已经game over了，不需要继续更新小行星精灵了，直到等待下一次方向键的时间触发 break; } } } } private void draw(Graphics g) { // 清屏 if (!isPaused) { g.setColor(0x000000); g.fillRect(0, 0, getWidth(), getHeight()); g.setColor(0x00ffff00);//为了显示计时的数字 g.drawString(String.valueOf(this.gametime), getWidth() / 2 - 15, 10, 0); // 画飞碟精灵 ufoSprite.paint(g); // 画小行星精灵 for (int i = 0; i < 5; i++) { roidSprite[i].paint(g); } } //绘制游戏结束 if (gameOver) { g.drawString("Game Over", 30, 85, Graphics.TOP | Graphics.LEFT); } //绘制暂停按钮文字 if (isPaused) { g.drawString(pauseStr, width, height, Graphics.RIGHT | Graphics.BOTTOM); } else { g.drawString(continueStr, width, height, Graphics.RIGHT | Graphics.BOTTOM); } // Flush the offscreen graphics buffer更新双缓存 flushGraphics(); } private void checkBounds(Sprite sprite) { // 折返精灵 if (sprite.getX() < -sprite.getWidth()) { sprite.setPosition(getWidth(), sprite.getY()); } else if (sprite.getX() > getWidth()) { sprite.setPosition(-sprite.getWidth(), sprite.getY()); } if (sprite.getY() < -sprite.getHeight()) { sprite.setPosition(sprite.getX(), getHeight()); } else if (sprite.getY() > getHeight()) { sprite.setPosition(sprite.getX(), -sprite.getHeight()); } } }