利用canvas畫一個動態時鐘
目標:利用canvas畫布畫一個動態時鐘,根據目前的時間可以實時更新的,可以在過程中新增一些效果,比如讓時鐘外圍的一圈顏色漸變,時鐘上的數字顏色改變,時鐘的指標顏色改變。。。
設定一個定時器
先放上一張效果圖,參考一下
先建一個畫布,寫好樣式
<style type="text/css">
*{
margin: 0;
padding: 0;
}
div{ //設定div的text-align為center,margin-top
text-align: center;
margin-top: 150px;
}
canvas{ //設定一下畫布的邊框
border: 1px solid #000;
}
</style>
<div> //設定一下畫布的寬高
<canvas id="canvas" width="500px" height="500px"></canvas>
</div>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d"); //畫布一般都是2d的
var width = canvas.width; //時鐘的寬高等於畫布的寬高,設定時鐘的半徑為畫布的一半,這樣時鐘就可以包含在畫布裡面
var height = canvas.height;
var r = height/2;
//接下來開始準備畫圓,畫圓的時候給圓加了漸變色,根據個人喜好,漸變色加在其他地方也可以,本人是把漸變色加在了這裡
var r1 = Math.floor(Math.random()*256); //讓顏色隨機,重新整理一下就可以變其他的顏色
var g1 = Math.floor(Math.random()*256);
var b1 = Math.floor(Math.random()*256);
var grd=ctx.createLinearGradient(0,0,0,r);
//函式
ctx.save() //儲存
ctx.translate(r,r);
ctx.beginPath(); //開始路徑
ctx.arc(0,0,r-5,0,Math.PI*2,false); //畫圓(原點座標,半徑設定的可以少一些,因為要加上框的大小,讓圓在畫布的寬高裡面,整個圓,方向設定為順時針,逆時針都可以)
ctx.closePath(); //關閉路徑
ctx.lineWidth = 10; //設定圓的線寬為10
grd.addColorStop(0,"rgb("+r1+","+g1+","+b1+")"); //設定的漸變色,可以設定的細膩一點,這裡我是從0-0.25-0.5-0.75-1設定的
grd.addColorStop(0.25,"rgb("+b1+","+g1+","+r1+")");
grd.addColorStop(0.5,"rgb("+g1+","+b1+","+r1+")");
grd.addColorStop(0.75,"rgb("+g1+","+b1+","+r1+")");
grd.addColorStop(1,"rgb("+g1+","+b1+","+r1+")");
ctx.strokeStyle=grd; //漸變色
ctx.stroke(); //
//下面開始新增時鐘上面的數字,圓一般是從0也就是時鐘的指標3那裡開始,把這些數字放在一個數組裡面,設定一下數字的字型大小,樣式,
var hoursnum = [3,4,5,6,7,8,9,10,11,12,1,2];
ctx.font = "20px Arial";
ctx.textAlign = "center";
ctx.textBaseline = "middle";
//下面開始設定時鐘上數字的顏色
for(var i = 0;i < hoursnum.length;i++){
var rad = 2 * Math.PI / 12 * i; //一整個圓,一共有12個數字,算出數字所在位置的弧度
var x = Math.cos(rad) * (r - 30); //判斷數字的座標,例如數字4,x=cos30度,y=sin30度,
var y = Math.sin(rad) * (r - 30);
ctx.fillText(hoursnum[i],x,y)
ctx.fillStyle = "red"; //可以設定一下顏色,在此處我設定的紅色
}
//現在開始設定數字之間的小間隙,此處實際上代表的是分的顏色
for(var j = 0;j < 60;j++){
var rad = 2 * Math.PI / 60 * j;
var x = Math.cos(rad) * (r - 15);
var y = Math.sin(rad) * (r - 15);
ctx.beginPath(); //開始路徑
if(j % 5 === 0){
ctx.fillStyle = "lightpink"; //把間隙之間的顏色判斷一下,設定不同的顏色,容易分辨
}else{
ctx.fillStyle = "darkred"
}
ctx.arc(x,y,2,0,Math.PI*2)
ctx.closePath(); //結束路徑
ctx.fill()
}
//設定時針
ctx.save();
ctx.beginPath();
ctx.lineWidth = 6;
var rad = Math.PI * 2 / 12 * hour;
var rad_minu = Math.PI * 2 / 12 / 60 * minu; //分針對時針會有影響,設定一下,消除分針對時針的影響
ctx.rotate(rad + rad_minu);
ctx.moveTo(0,10);
ctx.lineTo(0,-r/2);
ctx.lineCap="round"; //使用linecap屬性給兩端稍加一點弧度,看起來不是那麼生硬
ctx.strokeStyle = "darkred";
ctx.stroke()
ctx.restore()
//設定分針
ctx.save();
ctx.beginPath();
ctx.lineWidth = 4;
var rad = Math.PI * 2 / 60 * minu;
ctx.rotate(rad)
ctx.moveTo(0,10);
ctx.lineTo(0,-r+50);
ctx.lineCap="round";
ctx.strokeStyle = "#F0f101";
ctx.stroke()
ctx.restore()
//設定秒針
ctx.save();
var rad = Math.PI * 2 / 60 * seco;
ctx.beginPath();
ctx.rotate(rad)
ctx.fillStyle = "pink";
ctx.moveTo(-2,20);
ctx.lineTo(2,20);
ctx.lineTo(1,-r+20);
ctx.lineTo(-1,-r+20);
ctx.closePath()
ctx.fill()
ctx.restore()
//設定一個圓,把時針,分針,秒針固定著,看起來視覺效果好一些
ctx.beginPath();
ctx.fillStyle = "#f00"; //記得設定一個顏色
ctx.arc(0,0,5,0,Math.PI*2);
ctx.closePath();
ctx.fill()
//設定定時器,呼叫上面的時針,分針,秒針的函式
function draw(){
ctx.clearRect(0,0,width,height);
var datenow = new Date();
var hour = datenow.getHours();
var minu = datenow.getMinutes();
var seco = datenow.getSeconds();
fun()
drawHour(hour,minu)
drawMinu(minu)
drawSeco(seco)
drawDot()
ctx.restore()
}
draw()
setInterval(draw,1000)
此處附上程式碼
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>時鐘</title> <style type="text/css"> *{ margin: 0; padding: 0; } div{ text-align: center; margin-top: 150px; } canvas{ border: 1px solid #000; } </style> </head> <body> <div> <canvas id="canvas" width="500px" height="500px"></canvas> </div> <script type="text/javascript"> var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); var width = canvas.width; var height = canvas.height; var r = height/2; var r1 = Math.floor(Math.random()*256); var g1 = Math.floor(Math.random()*256); var b1 = Math.floor(Math.random()*256); var grd=ctx.createLinearGradient(0,0,0,r); function fun(){ ctx.save() ctx.translate(r,r); ctx.beginPath(); ctx.arc(0,0,r-5,0,Math.PI*2,false); ctx.closePath(); ctx.lineWidth = 10; grd.addColorStop(0,"rgb("+r1+","+g1+","+b1+")"); grd.addColorStop(0.25,"rgb("+b1+","+g1+","+r1+")"); grd.addColorStop(0.5,"rgb("+g1+","+b1+","+r1+")"); grd.addColorStop(0.75,"rgb("+g1+","+b1+","+r1+")"); grd.addColorStop(1,"rgb("+g1+","+b1+","+r1+")"); ctx.strokeStyle=grd; ctx.stroke(); var hoursnum = [3,4,5,6,7,8,9,10,11,12,1,2]; ctx.font = "20px Arial"; ctx.textAlign = "center"; ctx.textBaseline = "middle"; for(var i = 0;i < hoursnum.length;i++){ var rad = 2 * Math.PI / 12 * i; var x = Math.cos(rad) * (r - 30); var y = Math.sin(rad) * (r - 30); ctx.fillText(hoursnum[i],x,y) ctx.fillStyle = "red"; } for(var j = 0;j < 60;j++){ var rad = 2 * Math.PI / 60 * j; var x = Math.cos(rad) * (r - 15); var y = Math.sin(rad) * (r - 15); ctx.beginPath(); if(j % 5 === 0){ ctx.fillStyle = "darkred"; }else{ ctx.fillStyle = "lightpink" } ctx.arc(x,y,2,0,Math.PI*2) ctx.closePath(); ctx.fill() } } function drawHour(hour,minu){ ctx.save(); ctx.beginPath(); ctx.lineWidth = 6; var rad = Math.PI * 2 / 12 * hour; var rad_minu = Math.PI * 2 / 12 / 60 * minu; ctx.rotate(rad + rad_minu); ctx.moveTo(0,10); ctx.lineTo(0,-r/2); ctx.lineCap="round"; ctx.strokeStyle = "darkred"; ctx.stroke() ctx.restore() } function drawMinu(minu){ ctx.save(); ctx.beginPath(); ctx.lineWidth = 4; var rad = Math.PI * 2 / 60 * minu; ctx.rotate(rad) ctx.moveTo(0,10); ctx.lineTo(0,-r+50); ctx.lineCap="round"; ctx.strokeStyle = "#F0f101"; ctx.stroke() ctx.restore() } function drawSeco(seco){ ctx.save(); var rad = Math.PI * 2 / 60 * seco; ctx.beginPath(); ctx.rotate(rad) ctx.fillStyle = "pink"; ctx.moveTo(-2,20); ctx.lineTo(2,20); ctx.lineTo(1,-r+20); ctx.lineTo(-1,-r+20); ctx.closePath() ctx.fill() ctx.restore() } function drawDot(){ ctx.beginPath(); ctx.fillStyle = "#f00"; ctx.arc(0,0,5,0,Math.PI*2); ctx.closePath(); ctx.fill() } function draw(){ ctx.clearRect(0,0,width,height); var datenow = new Date(); var hour = datenow.getHours(); var minu = datenow.getMinutes(); var seco = datenow.getSeconds(); fun() drawHour(hour,minu) drawMinu(minu) drawSeco(seco) drawDot() ctx.restore() } draw() setInterval(draw,1000) </script> </body> </html>