html5 数字增长显示,HTML5效果：Canvas 实现圆形进度条并显示数字百分比

HTML5 Canvas 圆形进度条并显示数字百分比

window.οnlοad= 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 = 0.1; //加载的快慢就靠它了

//绘制5像素宽的运动外圈

functionblueCircle(n){

context.save();

context.strokeStyle= "#fff"; //设置描边样式

context.lineWidth = 5; //设置线宽

context.beginPath(); //路径开始

context.arc(centerX, centerY, 100 , -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();

}

//绘制白色外圈

functionwhiteCircle(){

context.save();

context.beginPath();

context.lineWidth= 2; //设置线宽

context.strokeStyle = "red";

context.arc(centerX, centerY, 100 , 0,Math.PI*2, false);

context.stroke();

context.closePath();

context.restore();

}

//百分比文字绘制

functiontext(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 = "#fff"; //设置描边样式

context.font = "40px Arial"; //设置字体大小和字体

//绘制字体，并且指定位置

context.strokeText(n.toFixed(0)+"%", centerX-25, centerY+10);

context.stroke(); //执行绘制

context.restore();

}

//动画循环

(functiondrawFrame(){window.requestAnimationFrame(drawFrame);

context.clearRect(0, 0, canvas.width, canvas.height);

whiteCircle();

text(speed);

blueCircle(speed);

if(speed > 100) speed = 0;

speed += 0.1;

}());

}