canvas動態時鐘效果

螞蟻小編發表於2018-07-03
Canvas
分享一段程式碼例項，它實現了動態時鐘效果。

此時鐘能夠動態的顯示當前時間，並自動走動。

程式碼例項如下:

[HTML] 純文字檢視 複製程式碼執行程式碼
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>螞蟻部落</title>
<style>
canvas {
  border:2px dotted #ccc;
}
</style>
</head>
<body>
<canvas id="canvas" width="550" height="450"></canvas>
<script type="text/javascript">
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
function clock() {
  var now = new Date();
  var ctx = document.getElementById('canvas').getContext('2d');
  ctx.save();
  ctx.clearRect(0, 0, 150, 150);
  ctx.translate(75, 75);
  ctx.scale(0.4, 0.4);
  ctx.rotate(-Math.PI / 2);
  ctx.strokeStyle = "black";
  ctx.fillStyle = "white";
  ctx.lineWidth = 8;
  ctx.lineCap = "round";
 
  // Hour marks
  ctx.save();
  for (var i = 0; i < 12; i++) {
    ctx.beginPath();
    ctx.rotate(Math.PI / 6);
    ctx.moveTo(100, 0);
    ctx.lineTo(120, 0);
    ctx.stroke();
  }
  ctx.restore();
 
  // Minute marks
  ctx.save();
  ctx.lineWidth = 5;
  for (i = 0; i < 60; i++) {
    if (i % 5 != 0) {
      ctx.beginPath();
      ctx.moveTo(117, 0);
      ctx.lineTo(120, 0);
      ctx.stroke();
    }
    ctx.rotate(Math.PI / 30);
  }
  ctx.restore();
 
  var sec = now.getSeconds();
  var min = now.getMinutes();
  var hr = now.getHours();
  hr = hr >= 12 ? hr - 12 : hr;
 
  ctx.fillStyle = "black";
 
  // write Hours
  ctx.save();
  ctx.rotate(hr * (Math.PI / 6) + (Math.PI / 360) * min + (Math.PI / 21600) * sec)
  ctx.lineWidth = 14;
  ctx.beginPath();
  ctx.moveTo(-20, 0);
  ctx.lineTo(80, 0);
  ctx.stroke();
  ctx.restore();
 
  // write Minutes
  ctx.save();
  ctx.rotate((Math.PI / 30) * min + (Math.PI / 1800) * sec)
  ctx.lineWidth = 10;
  ctx.beginPath();
  ctx.moveTo(-28, 0);
  ctx.lineTo(112, 0);
  ctx.stroke();
  ctx.restore();
 
  // Write seconds
  ctx.save();
  ctx.rotate(sec * Math.PI / 30);
  ctx.strokeStyle = "#D40000";
  ctx.fillStyle = "#D40000";
  ctx.lineWidth = 6;
  ctx.beginPath();
  ctx.moveTo(-30, 0);
  ctx.lineTo(83, 0);
  ctx.stroke();
  ctx.beginPath();
  ctx.arc(0, 0, 10, 0, Math.PI * 2, true);
  ctx.fill();
  ctx.beginPath();
  ctx.arc(95, 0, 10, 0, Math.PI * 2, true);
  ctx.stroke();
  ctx.fillStyle = "rgba(0,0,0,0)";
  ctx.arc(0, 0, 3, 0, Math.PI * 2, true);
  ctx.fill();
  ctx.restore();
 
  ctx.beginPath();
  ctx.lineWidth = 14;
  ctx.strokeStyle = '#325FA2';
  ctx.arc(0, 0, 142, 0, Math.PI * 2, true);
  ctx.stroke();
 
  ctx.restore();
 
  window.requestAnimationFrame(clock);
}
window.requestAnimationFrame(clock);
</script>
</body>
</html>

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