下面的代码为选取框设置动画。动画开始很快,但随着时间的推移明显减慢。请帮我弄清楚原因。相同的代码在这里:http: //jsbin.com/aleqef/
编辑:我在动画循环期间没有创建任何新对象,一切似乎都被缓存了,即模式、上下文等。我只是没有看到任何可疑的东西。看起来像内存问题,但我不知道为什么。
var data = [
"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAYAAAAGCAMAAADXEh96AAAABGdBTUEAAK/INwWK6QAAABl0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAAGUExURQAAAP///6XZn90AAAAcSURBVHjaYmBgYGBkZAQSYAjlgUXgYhAeQIABAAGkABPpfLrFAAAAAElFTkSuQmCC",
"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAYAAAAGCAMAAADXEh96AAAABGdBTUEAAK/INwWK6QAAABl0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAAGUExURQAAAP///6XZn90AAAAeSURBVHjaYmBkAEEgYGRkBBEgFgMDRBTGA8sBBBgAAaQAE03fiAgAAAAASUVORK5CYII=",
"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAYAAAAGCAMAAADXEh96AAAABGdBTUEAAK/INwWK6QAAABl0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAAGUExURQAAAP///6XZn90AAAAdSURBVHjaYmBgZGRkYGAAY0YGCITxoHIQUYAAAwABpAATvSsONQAAAABJRU5ErkJggg=="
];
var context = document.getElementById("canvas").getContext("2d");
var count = data.length;
var patterns = [];
var pattern = 0;
function onload(e) {
patterns.push(context.createPattern(e.target, "repeat"));
}
function draw() {
for (var angle = 0; angle < 360; angle += 5) {
var rad = (angle * Math.PI) / 180;
var x = 200 * Math.cos(rad);
var y = 200 * Math.sin(rad);
context.moveTo(0, 0);
context.lineTo(x, y);
}
}
function animate() {
window.setTimeout(animate, 1000 / 60);
if (patterns.length > 0) {
context.clearRect(0, 0, context.canvas.width, context.canvas.height);
draw();
context.lineWidth = 1;
context.strokeStyle = patterns[pattern];
context.stroke();
pattern = (pattern + 1) % patterns.length;
}
}
for (var i = 0; i < count; i++) {
var image = new Image();
image.onload = onload;
image.src = data[i];
}
animate();