测量应用程序/线程花费的时间

发布于 2024-08-29 00:57:33 字数 702 浏览 5 评论 0原文

我正在用 Java 编写一个模拟，其中物体在牛顿物理学下起作用。一个物体可能会受到一个力的作用，所产生的速度会导致它在屏幕上移动。模拟的本质意味着对象以离散的步骤移动，具体取决于动画循环的当前迭代和上一次迭代之间经过的时间；例如，

public void animationLoop() {
  long prev = System.currentTimeMillis();
  long now;

  while(true) {
    long now = System.currentTimeMillis();
    long deltaMillis = now - prev;
    prev = now;

    if (deltaMillis > 0) { // Some time has passed
      for (Mass m : masses) {
        m.updatePosition(deltaMillis);
      }

      // Do all repaints.
    }
  }
}

如果动画线程以某种方式延迟，导致大量时间流逝（经典情况是在 Windows 下，单击并按住最小化/最大化可防止重新绘制），就会出现问题，这会导致对象以惊人的速度移动。我的问题：有没有办法确定动画线程中花费的时间而不是挂钟时间，或者有人可以建议一种解决方法来避免此问题？

到目前为止，我唯一的想法是通过某个上限来限制 deltaMillis 。

原文

I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g

public void animationLoop() {
  long prev = System.currentTimeMillis();
  long now;

  while(true) {
    long now = System.currentTimeMillis();
    long deltaMillis = now - prev;
    prev = now;

    if (deltaMillis > 0) { // Some time has passed
      for (Mass m : masses) {
        m.updatePosition(deltaMillis);
      }

      // Do all repaints.
    }
  }
}

A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem?

My only thought so far is to contstrain deltaMillis by some upper bound.

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樱花细雨 2024-09-05 00:57:33

您是否考虑过使用计时器之类的东西而不是循环旋转？

TimerTask tt = new TimerTask(){
  long prev = System.currentTimeMillis();
  public void run(){
    long now = System.currentTimeMillis();
    for (Mass m : masses) {
      m.updatePosition(now-prev);
    }
    prev = now;
  }
}

new Timer(true).schedule(tt, 1000, 1000) ;

这样，您至少可以保证在对象更新之间有一些延迟，因此您不应该像 while(true) 循环那样连续进行一堆重绘，并且如果线程延迟，您将不会立即重新绘制- 任务的执行，来自文档：“在固定延迟执行中，每次执行都是相对于前一次执行的实际执行时间来安排的。”

Have you considered using something like a timer instead of spinning in a loop?

TimerTask tt = new TimerTask(){
  long prev = System.currentTimeMillis();
  public void run(){
    long now = System.currentTimeMillis();
    for (Mass m : masses) {
      m.updatePosition(now-prev);
    }
    prev = now;
  }
}

new Timer(true).schedule(tt, 1000, 1000) ;

This way you are guaranteed to at least have some delay between the update of your objects so you shouldn't have a bunch of repaints consecutively as with the while(true) loop, and if the thread is delayed you will not got an immediate re-execution of the task, from the docs: "In fixed-delay execution, each execution is scheduled relative to the actual execution time of the previous execution."

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