会走动的图形html5时钟示例_html5教程技巧

Clock.prototype = {
constructor: Clock,
drawCircle: function () {
var ctx = this.ctx;
ctx.strokeStyle = "black";
ctx.arc(this.canvas.width / 2, this.canvas.height / 2, 50, 0, 2 * Math.PI, false);
ctx.stroke();
},
drawNum: function () {
var ctx = this.ctx;
var angle = Math.PI * 2 / 12;
for (var i = 1; i ctx.font = "20px Georgia";
ctx.textAlign = "center";
ctx.textBaseline = 'middle';
ctx.fillText(String(i), this.canvas.width / 2 + Math.cos(3 *Math.PI / 2 + angle * i) * 40, this.canvas.height / 2 + Math.sin(3 * Math.PI / 2 + angle * i) * 40);
}
},
drawPointer: function () {
var ctx = this.ctx;
var that = this;
var date, hour, minute, second;
date = new Date();
hour = date.getHours();
if (hour > 12) {
hour = hour % 12;
}
minute = date.getMinutes();
second = date.getSeconds();

var b = minute * Math.PI / 30;
var c = second * Math.PI / 30;
var a = hour * Math.PI / 6 + Math.PI / 6 * minute / 60;
var minuteAngle = Math.PI * 2 / 3600;
var secondAngle = Math.PI * 2 / 60;
var hourAngle = Math.PI * 2 / 12 / 3600;

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ctx.beginPath();
ctx.save();
ctx.translate(that.canvas.width / 2, that.canvas.height / 2);
ctx.arc(0, 0, 3, 0, 2 * Math.PI, false);
ctx.fill();
ctx.closePath();
ctx.beginPath();
a += hourAngle;
ctx.rotate(a);
ctx.fillRect(-2, -22, 4, 30);
ctx.closePath();
ctx.beginPath();
b += minuteAngle;
ctx.rotate(b - a);
ctx.fillRect(-1.5, -26, 3, 35);
ctx.closePath();
ctx.beginPath();
c += secondAngle;
ctx.rotate(c - b);
ctx.fillRect(-1, -30, 2, 40);
ctx.closePath();
ctx.restore();
},
rePaint: function () {
this.drawPointer();
this.drawCircle();
this.drawNum();
},
tik: function () {
var that = this;
var ctx = this.ctx;
this.rePaint();
window.timer = setInterval(function () {
ctx.clearRect(0, 0, that.canvas.width, that.canvas.height);
that.rePaint();
}, 1000);
}
};

var options;
var clock = new Clock(document.getElementById("canvas"), options);
clock.tik();