Javascript 如何在画布中复制动画

我画了一个半圆的动画，我基本上想复制它，然后将副本向下移动60像素，然后给新的一个添加一秒钟的延迟，这样它就可以画一个B

html

剧本

var can = document.getElementById('thecanvas');
ctx = can.getContext('2d');
can.width = window.innerWidth;
can.height = window.innerHeight;

window.drawCircle = function (x, y) {
    segments = 90, /* how many segments will be drawn in the space */
    currentSegment = 0,
    toRadians = function (deg) {
        return (Math.PI / 180) * deg;
    },
    getTick = function (num) {
        var tick = toRadians(180) / segments; /*360=full, 180=semi, 90=quarter... */
        return tick * num;
    },
    segment = function (end) {
        end = end || getTick(currentSegment);
        ctx.clearRect(0, 0, can.width, can.height);
        ctx.beginPath();
        ctx.arc(x, y, 60, (1.5 * Math.PI), end + (1.5 * Math.PI), false);
        ctx.stroke();
        ctx.closePath();
    };

    ctx.lineWidth = 5;
    ctx.strokeStyle = 'rgba(0,0,0,0.5)';

    setTimeout(function render() {
        segment(getTick(currentSegment));
        currentSegment += 1;
        if (currentSegment < segments) {
            setTimeout(render, 5);
        } else {
            currentTick = 0;
        }
    }, 250);
};
drawCircle(100, 100); 

这里有一把小提琴

首先，您可以将setTimeout函数置于drawCircle方法之外

那么您至少有两个选项：

创建endDraw事件，该事件将在1次绘图结束时调度。当这个事件是handle时，只需再次调用drawCircle方法。要实现这一点，当然需要一个main方法来调用第一个drawCircle

为了获得更好的解决方案，您可以描述呼叫的工作流。ie描述要调用的方法列表，以及每个方法的开始帧：

var workflow = [{method:"drawCircle", frame:0, x:100, y:100},      //the first half circle at the frame 0, x=100, y=100
                {method:"drawCircle", frame:1000, x:100, y:190}];  //the second half circle starting at frame 1000, x=100, y=190

您的主计时器将被配置为使用此阵列来知道要执行的调用

var workflow = [{method:"drawCircle", frame:0, x:100, y:100},      //the first half circle at the frame 0, x=100, y=100
                {method:"drawCircle", frame:1000, x:100, y:190}];  //the second half circle starting at frame 1000, x=100, y=190