使用MIDP2.0开发游戏(7)设计Scheduler

以下的Scheduler的实现参考自Marshall "Game PRogramming Gems 3"中的C++代码：

package game.engine.core;

public class Scheduler {

    // clock:
    private Clock clock = new Clock();
    
    // 启动Scheduler:
    public void start() {
        clock.start();
    }

    // 停止Scheduler:
    public void stop() {
        clock.stop();
    }

    public int getSystemTime() {
        return clock.getSystemTime();
    }

    public int getVirtualTime() {
        return clock.getVirtualTime();
    }

    // 执行完整的一帧：
    public void executeFrame() {
        System.out.println("-- start execute frame --");
        clock.beginFrame();
        int started = clock.getSystemTime();
        // do time task:
        System.out.println("doing time tasks...");
        try {
            Thread.sleep(500);
        }catch(InterruptedException ie) {}
        clock.advanceToEnd();
        // do frame task:
        System.out.println("doing frame tasks...");
        try {
            Thread.sleep(200);
        }catch(InterruptedException ie) {}
        // do render task:
        int end = clock.getSystemTime();
        int elapsed = end - started;
        int frameLength = clock.getFrameEnd() - clock.getFrameStart();
        System.out.println("elapsed: " + elapsed + ", frame: " + frameLength);
        System.out.println("cpu usage: " + (elapsed * 100 / frameLength) + "%");
        // cleanup:
        System.out.println("-- end execute frame --/n");
    }