前言
用HTML画出可动画的圆环.效果图如下:
详细代码CanvasForHtml5已上传到Github
分析
<canvas id="canvas" width="600" height="600" style="background: "#ffffff";" ></canvas>
<script>
window.onload = function(){
var canvas = document.getElementById('canvas'), //获取canvas元素
context = canvas.getContext('2d'), //获取画图环境，指明为2d
centerX = canvas.width/2, //Canvas中心点x轴坐标
centerY = canvas.height/2, //Canvas中心点y轴坐标
rad = Math.PI*2/100, //将360度分成100份，那么每一份就是rad度
speed = 10; //加载的快慢就靠它了
canvas.onclick=function (){
window.open('flightHour.html');
}
//绘制外圈
function blueCircle(n){
context.save();
context.strokeStyle = "#A757A8"; //设置描边样式
context.lineCap="round";
context.radius=30;
context.lineWidth = 30; //设置线宽
context.beginPath(); //路径开始
context.arc(centerX, centerY, 200 , -Math.PI/2, -Math.PI/2 +n*rad,false); //用于绘制圆弧context.arc(x坐标，y坐标，半径，起始角度，终止角度，顺时针/逆时针)
context.stroke(); //绘制
context.closePath(); //路径结束
context.restore();
}
//绘制内圈
function whiteCircle(){
context.save();
context.beginPath();
context.radius=20;
context.lineWidth = 20;
context.strokeStyle = "gray";
context.arc(centerX, centerY, 200 , 0, Math.PI*2, false);
context.stroke();
context.closePath();
context.restore();
}
//文字绘制
function text(n){
context.save(); //save和restore可以保证样式属性只运用于该段canvas元素
context.strokeStyle = "#808080"; //设置描边样式
context.fillStyle="#808080";
context.font = "60px sans-serif"; //设置字体大小和字体
//绘制字体，并且指定位置
context.fillText("966", centerX-45, centerY-20);
context.font = "40px sans-serif";
context.fillText("总数", centerX-45, centerY+40);
context.stroke(); //执行绘制
context.restore();
}
//动画循环
(function drawFrame(){
window.requestAnimationFrame(drawFrame, canvas);
context.clearRect(0, 0, canvas.width, canvas.height);
whiteCircle();
text(speed);
blueCircle(speed);
if(speed>0&&speed<88) {
speed += 1;
}else{
speed=88;
}
}());
}
</script>
结语
博客旧版原文在CSDN上:https://blog.csdn.net/luochuanAD/article/details/73251792
