Question

我有一个线程，每秒重复一次动作（射击）：

long lasttime;
Creature owner;
public Attacker(Creature actor)
{
    super("Attacker - "+actor.getClass().getSimpleName());
    lasttime=System.currentTimeMillis();    
    owner=actor;
    owner.lockedon=true;
}
@Override
public void run() {
    super.run();
    while(!owner.dead && owner.lockedon)
    {
        List pl=TVS.getGameScreen().projectiles;
        synchronized (pl)
        {
           //here
            long curtime=System.currentTimeMillis();
            if(curtime-lasttime>1000)
            {
                owner.attack();
                lasttime=curtime;
            }
        }
    }
}

但是当主程序线程减慢时，此线程执行速度比main快，并且相对于主线程，射击变得过于频繁。我该怎么办？

Answer 1

您正忙着等待，持有可能消耗大量CPU的锁，或者锁定试图使用相同锁的其他线程。我建议像

这样的东西

while(!owner.dead && owner.lockedon) {
    List pl=TVS.getGameScreen().projectiles;
    long curtime=System.currentTimeMillis();
    long remaining = 1000 - (curtime-lasttime);
    if(remaining <= 0) {
        synchronized (pl) { // only lock when needed.
            owner.attack();
            lasttime=curtime;
        }
    } else {
        // when not doing something useful, give up the CPU to another thread.
        Thread.sleep(remaining);
    }
}

Answer 2

我宁愿使用计时器，因为它们更容易维护并且更准确：

Timer shooterTimer = new Timer();
shooterTimer.scheduleAtFixedRate(
    new TimerTask() {
        @Override
        public void run() {
            if (!owner.dead && owner.lockedon) {
                List pl = TVS.getGameScreen().projectiles;
                synchronized (pl) {
                    onwer.attack();
                }
            }
        }
    },
    0,     // Start the timer now
    1000); // Execute the task every second

一个线程时间比其他时间更快

2 个答案: