js實現圓環百分比載入等待效果程式碼例項

admin發表於2017-02-13
JS
本章節分享一段程式碼例項，它實現了圓環百分比載入等待效果。

程式碼例項如下:

[HTML] 純文字檢視 複製程式碼
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>螞蟻部落</title>
<style>
*{
  padding: 0; 
  margin: 0;
}
.circle{
  width: 200px;
  height: 200px;
  margin: 20em auto;
  position: relative;
}
canvas{
  display: block;
  margin: 0;
  position: absolute;
  background: white;
  left: 0;
  top: 0;
}
#canvas_1{z-index: 1 }
#canvas_2{
  z-index: 2; 
  background: transparent;
  transform:rotate(-90deg); 
}
</style>
</head>
<body>
<div class="circle">
  <canvas id="canvas_1" width="200" height="200"></canvas>
  <canvas id="canvas_2" width="200" height="200"></canvas>
</div>
<script>
function inte(percent) {
  var canvas_1 = document.querySelector('#canvas_1');
  var canvas_2 = document.querySelector('#canvas_2');
  var ctx_1 = canvas_1.getContext('2d');
  var ctx_2 = canvas_2.getContext('2d');
  ctx_1.lineWidth = 10;
  ctx_1.strokeStyle = "#ccc";
  //畫底部的灰色圓環
  ctx_1.beginPath();
  ctx_1.arc(canvas_1.width / 2, canvas_1.height / 2, canvas_1.width / 2 - ctx_1.lineWidth / 2, 0, Math.PI * 2, false);
  ctx_1.closePath();
  ctx_1.stroke();
  if (percent < 0 || percent > 100) {
    throw new Error('percent must be between 0 and 100');
    return
  }
  ctx_2.lineWidth = 10;
  ctx_2.strokeStyle = "#f90";
  var angle = 0;
  var timer;
  (function draw() {
    timer = requestAnimationFrame(draw);
    ctx_2.clearRect(0, 0, canvas_2.width, canvas_2.height)
      //百分比圓環
    ctx_2.beginPath();
    ctx_2.arc(canvas_2.width / 2, canvas_2.height / 2, canvas_2.width / 2 - ctx_2.lineWidth / 2, 0, angle * Math.PI / 180, false);
    angle++;
    var percentAge = parseInt((angle / 360) * 100)
    if (angle > (percent / 100 * 360)) {
      percentAge = percent
      window.cancelAnimationFrame(timer);
    };
    ctx_2.stroke();
    ctx_2.closePath();
    ctx_2.save();
    ctx_2.beginPath();
    ctx_2.rotate(90 * Math.PI / 180)
    ctx_2.font = '30px Arial';
    ctx_2.fillStyle = 'red';
    var text = percentAge + '%';
    ctx_2.fillText(text, 80, -90);
    ctx_2.closePath();
    ctx_2.restore();
  })()
}
window.onload = inte(60);
</script>
</body>
</html>

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