javascript - 为什么 cancelAnimationFrame 不起作用？

Question

引用这个 fiddle - http://jsfiddle.net/rnqLfz14/28/

[此代码不是我的 - http://www.isaacsukin.com/news/2015/01/detailed-explanation-javascript-game-loops-and-timing ]

//....

function stop() {
    running = false;
    started = false;
    cancelAnimationFrame(frameID);
}

//...

function mainLoop(timestamp) {
    // Throttle the frame rate.
    if (timestamp < lastFrameTimeMs + (1000 / maxFPS)) {
        frameID = requestAnimationFrame(mainLoop);
        return;
    }
    delta += timestamp - lastFrameTimeMs;
    lastFrameTimeMs = timestamp;

    begin(timestamp, delta);

    if (timestamp > lastFpsUpdate + 1000) {
        fps = 0.25 * framesThisSecond + 0.75 * fps;

        lastFpsUpdate = timestamp;
        framesThisSecond = 0;
    }
    framesThisSecond++;

    var numUpdateSteps = 0;
    while (delta >= timestep) {
        update(timestep);
        delta -= timestep;
        if (++numUpdateSteps >= 240) {
            panic();
            break;
        }
    }

    draw(delta / timestep);

    T.textContent = timestamp;

    if (timestamp >= 6000.0) {
        T.textContent = "Stopped!";
        stop();
    }

    end(fps);

    frameID = requestAnimationFrame(mainLoop);
}
//...

cancelAnimationFrame 函数没有停止动画循环。有什么建议吗？我已经摸索了很长时间了，请提出任何建议，我们将不胜感激。

Answer 1

当满足 stop() 的条件时，将调用 stop() 但代码会继续执行，因此将请求新的 rAF。

只需在 stop 调用后添加一个 return 来防止这种情况发生(或使用 else):

...
if (timestamp >= 6000.0) {
    T.textContent = "Stopped!";
    stop();  // stop() is just a sub-routine here and will continue after being called
    return;  // <--- here
}
...

Modified fiddle