maincanvas.java

《j2me开发精解〉（詹健飞）CD-rom附带源码。用netbeans

package com.j2medev.chapter5.game;

import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class MainCanvas extends GameCanvas implements Runnable,CommandListener {
    private ScrollScreen midlet = null;
    private boolean isPlay;
    private long delay; //线程休眠的时间间隔
    private int width; // 屏幕宽度
    private int height; //屏幕高度
    private int scnX, scnY; //可视窗口的左上角坐标
    
    Image backgroundImage;
    private Sprite backgroundSprite;
    private LayerManager layerManager;
    
    public static final Command exitCommand = new Command("退出",Command.EXIT, 1);
    
    public MainCanvas(ScrollScreen midlet) throws Exception {
        super(true);
        this.midlet = midlet;
        width = getWidth();
        height = getHeight();
        scnX = 55;
        scnY = 20;
        delay = 20;
        backgroundImage = Image.createImage("/background.png");
        backgroundSprite = new Sprite(backgroundImage);
        layerManager = new LayerManager();
        layerManager.append(backgroundSprite);
        this.addCommand(exitCommand);
        this.setCommandListener(this);
    }
    
    public void start() {
        isPlay = true;
        //启动游戏线程
        Thread t = new Thread(this);
        t.start();
    }
    
    public void stop() {
        isPlay = false;
    }
    //游戏主循环
    public void run() {
        Graphics g = getGraphics();
        while (isPlay == true) {
            input();
            drawScreen(g);
            try {
                //线程休眠
                Thread.sleep(delay);
            } catch (InterruptedException ie) {
            }
        }
    }
    //处理用户输入 支持四个方向的屏幕滚动
    private void input() {
        int keyStates = getKeyStates();
        //根据用户输入调整scnX和scnY的值
        if ((keyStates & LEFT_PRESSED) != 0) {
            if (scnX - 1 > 0)
                scnX--;
        }else if ((keyStates & RIGHT_PRESSED) != 0) {
            if (scnX + 1 + 140 < backgroundImage.getWidth())
                scnX++;
        }else if((keyStates & UP_PRESSED)!=0){
            if(scnY -1 > 0){
                scnY--;
            }
        }else if((keyStates & DOWN_PRESSED)!=0){
            if(scnY+1+140<backgroundImage.getHeight()){
                scnY++;
            }
        }
    }
    
    private void drawScreen(Graphics g) {
        //清屏
        g.setColor(0xffffff);
        g.fillRect(0, 0, getWidth(), getHeight());
        g.setColor(0x0000ff);
        //设置视窗
        layerManager.setViewWindow(scnX, scnY, 140, 140);
        layerManager.paint(g, 20, 20);
        //绘制到主屏幕
        flushGraphics();
    } 
    
    public void commandAction(Command cmd,Displayable displayable){
        if(cmd == exitCommand){
            //停止线程，销毁MIDlet
            stop();
            midlet.exit();
        }
    }
}