不使用setInterval能正常画图,但是如果给画图部分套上setInterval(function(){画图},6000) 以后,就画不出来了。 我在画图函数的各个位置都设置了alert,各个参数都正确地传递了。但是图就是画不出来。
window.onload = function (){
var canvas = document.createElement('canvas');
var canvas_width = $("body").css("width").split("p")[0];
var canvas_height = $("body").css("height").split("p")[0];
document.body.appendChild(canvas);
canvas.id='homePageCanvas';
canvas.width = canvas_width;
canvas.height = canvas_height;
canvas.style.display="none";
var ctx1 = document.getElementById('homePageCanvas');
var ctx=ctx1.getContext("2d");
var hei=canvas.height;
var wid=canvas_width; //传递body尺寸
var heartSize; //心的大小
var color= [
["#FDE09A","#F3A7AC","#F29A63","#EB6161","#D8220D"],
["#FFE67A","#B4D78D","#00989E","#F6AC1A","#D8220D"],
["#D9C7C9","#B38893","#C6A7BE","#8D6982","#D8220D"],
["#FFE67A","#00989E","#B4D78D","#F6AC1A","#D8220D"],
["#E0F1F4","#9BCB60","#629A30","#49BCBD","#9F0052"],
["#FBCB72","#E9528E","#F39700","#E61C64","#E7242E"],
["#6BC8F2","#FFF8A5","#F19DB4","#5064AE","#E61C64"],
["#EBF5EB","#EE869A","#A2D7DD","#CBE3AE","#00AACE"],
["#8AC782","#9E4F1E","#EF8453","#F8C499","#007746"],
["#EFEB56","#008CD6","#6CBB5A","#EB6EA0","#6F186E"]];
//颜色数组
var posAndSize=Math.floor(Math.random()*2);//决定取哪一组“坐标数组和尺寸数组”
//坐标数组
var pos=[[[1,1.5],[2,2],[4,5],[1,5],[2,4],[6,3],[8,1.7],[9,5]],
[[1,2],[3,2],[4,4],[1,4],[2,3],[6,3],[8,3],[9,4]]];
//尺寸数组
var size=[[0.109375,0.109375,0.109375,0.08984375,0.08984375,0.2015625,0.140234375,0.08984375],
[0.109375,0.125,0.109375,0.08984375,0.08984375,0.2015625,0.140234375,0.08984375]];
//决定取哪一组颜色 0到9之间的整数
var bColor=Math.floor(Math.random()*10+0);
//画背景
ctx.fillStyle=color[bColor][0];
ctx.fillRect(0,0,wid,hei);
//以下是出问题的部分,把setinterval( function(){},6000)拿掉,则画图正常
setInterval(function(){
for(var i=0;i<8;i++){
//心形的坐标
var initX=(wid/10)*(pos[posAndSize][i][0]);
var initY=(hei/6)*(pos[posAndSize][i][1]);
//心形的尺寸,旋转角度,颜色
var heartSize=size[posAndSize][i]*wid/2.2;
var rotateAng=Math.floor(Math.random()*80+(-40))*Math.PI/180;
var colorX=color[bColor][Math.floor(Math.random()*4)+1];
//
//画心形
ctx.save();
ctx.beginPath();
heartCurve(initX,initY,heartSize,rotateAng,colorX);
ctx.restore();
}
},6000);
function heartCurve(initX,initY,heartSize,rotateAng,color){
this.centryX=initX;
this.centryY=initY;
this.heartSize=heartSize;
this.rotateAng=rotateAng;
this.color=color;
//alert(this.centryX);
var x = 1, y;
//alert(x);
//alert(this.heartSize);
ctx.translate(this.centryX,this.centryY);
ctx.rotate(rotateAng);
ctx.fillStyle = this.color;
ctx.beginPath();
//alert(x);
do {
y = -this.heartSize*0.8*(Math.sqrt(1-x*x) + Math.pow(x*x,1/3));
x -= 0.001;
ctx.lineTo(this.heartSize*x,y);
} while ( x >= -1 );
//alert(x);
do {
y = this.heartSize*0.8*(Math.sqrt(1-x*x) - Math.pow(x*x,1/3));
x += 0.001;
ctx.lineTo(this.heartSize*x,y);
} while ( x <= 1 );
//alert(x);
ctx.closePath();
//alert(this.color);
//alert(this.color);
ctx.fill();
//alert(color);
}
//把画的图设为背景
document.body.style.background = "url('"+homePageCanvas.toDataURL()+"')";
document.body.style.backgroundPosition="center";
document.body.style.backgroundRepeat="no-repeat";
document.body.style.backgroundAttachment="fixed";
}