canvas繪製鬧鐘-方法2
阿新 • • 發佈：2018-11-27
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>canvas</title> <style> #clock{border:1px solid #ccc} </style> </head> <body> <canvas id="clock" width="300" height="300"></canvas> </body> <script type="text/javascript"> var canvas = document.querySelector("#clock"); var ctx = canvas.getContext("2d") var canvasWidth = ctx.canvas.width; var canvasHeight = ctx.canvas.height; console.log(canvasWidth,canvasHeight) var r = canvasWidth/2; var rem = canvasWidth/200 //設定縮放時鐘的比例 function drawBackground(){ ctx.save() ctx.beginPath(); ctx.translate(r,r); ctx.strokeStyle = "#257cc0"; ctx.lineWidth = 8*rem; ctx.arc(0,0,r-ctx.lineWidth/2,0,2*Math.PI,true) //true是逆時針 ctx.stroke() //一定要寫，否則不知道是填充還是描邊 //畫數字1-12 var hoursNumbers =[3,4,5,6,7,8,9,10,11,12,1,2]; ctx.font=18*rem + "px Arial";//除了大小一定要加字型型別 ctx.textAlign="center"; ctx.textBaseline="middle"; hoursNumbers.forEach(function(number,i){ var rad = 2*Math.PI/12*i var x = Math.cos(rad)*(r-30*rem); var y = Math.sin(rad)*(r-30*rem); ctx.fillText(number,x,y) }) //畫刻度 for(var i=0;i<60;i++){ var rad = 2*Math.PI/60*i; var x =Math.cos(rad)*(r-16*rem); var y = Math.sin(rad)*(r-16*rem); ctx.beginPath() if(i%5==0){ ctx.fillStyle="#333" }else{ ctx.fillStyle="#999" } ctx.arc(x,y,2*rem,0,2*Math.PI,false); ctx.fill() } } function drawHour(hour,minute){ ctx.save(); ctx.beginPath(); var rad = 2*Math.PI/12*hour; var mrad = 2*Math.PI/12/60*minute; ctx.rotate(rad+mrad) ctx.lineWidth = 6*rem; ctx.lineCap ="round"; ctx.moveTo(0,10*rem); ctx.lineTo(0,-r/2) ctx.stroke(); ctx.restore(); } function drawMinute(minute){ ctx.save(); ctx.beginPath(); var rad = 2*Math.PI/60*minute; ctx.rotate(rad) ctx.lineWidth = 4*rem; ctx.lineCap ="round"; ctx.moveTo(0,10*rem); ctx.lineTo(0,-r+40*rem) ctx.stroke(); ctx.restore(); } function drawSecond(second){ ctx.save(); ctx.beginPath(); ctx.fillStyle="orange"; var rad = 2*Math.PI/60*second; ctx.rotate(rad) ctx.moveTo(-2*rem,20*rem); ctx.lineTo(2*rem,20*rem); ctx.lineTo(1,-r+18*rem) ctx.lineTo(-1,-r+18*rem); ctx.fill() ctx.restore(); } function drawDot(){ ctx.beginPath(); ctx.fillStyle="#fff"; ctx.arc(0,0,4*rem,0,2*Math.PI,false); ctx.fill(); } function draw(){ ctx.clearRect(0,0,canvasWidth,canvasHeight) var now = new Date(); var hour = now.getHours(); var minute = now.getMinutes(); var second = now.getSeconds(); drawBackground(); drawHour(hour,minute); drawMinute(minute); drawSecond(second); drawDot(); ctx.restore(); window.requestAnimationFrame(draw) } draw(); //setInterval(draw,1000); </script> </html>