本文介紹了HTML5 Canvas 實現圓形進度條並顯示數字百分比效果示例，具體如下：
實現效果
1.首先創建html代碼
<canvas id=canvas width=500 height=500 style=background:#000;></canvas>
2.創建canvas環境
var canvas = document.getElementById('canvas'), //獲取canvas元素context = canvas.getContext('2d'), //獲取畫圖環境，指明為2d centerX = canvas.width/2, //Canvas中心點x軸坐標centerY = canvas.height/2, //Canvas中心點y軸坐標rad = Math.PI*2/100, //將360度分成100份，那麼每一份就是rad度speed = 0.1; / /加載的快慢就靠它了3.繪製5像素寬的運動外圈
//繪製5像素寬的運動外圈function blueCircle(n){ context.save(); context.strokeStyle = #fff; //設置描邊樣式context.lineWidth = 5; //設置線寬context.beginPath( ); //路徑開始context.arc(centerX, centerY, 100 , -Math.PI/2, -Math.PI/2 +n*rad, false); //用於繪製圓弧context.arc(x坐標，y坐標，半徑，起始角度，終止角度，順時針/逆時針) context.stroke(); //繪製context.closePath(); //路徑結束context.restore(); }4.繪製白色外圈
//繪製白色外圈function whiteCircle(){ context.save(); context.beginPath(); context.lineWidth = 2; //設置線寬context.strokeStyle = red; context.arc(centerX, centerY, 100 , 0, Math.PI*2, false); context.stroke(); context.closePath(); context.restore(); }5.百分比文字繪製
function text(n){ context.save(); //save和restore可以保證樣式屬性只運用於該段canvas元素context.strokeStyle = #fff; //設置描邊樣式context.font = 40px Arial; //設置字體大小和字體//繪製字體，並且指定位置context.strokeText(n.toFixed(0)+%, centerX-25, centerY+10); context.stroke(); //執行繪製context.restore() ; }6.讓它運動起來
//動畫循環(function drawFrame(){ window.requestAnimationFrame(drawFrame); context.clearRect(0, 0, canvas.width, canvas.height); whiteCircle(); text(speed); blueCircle(speed); if( speed > 100) speed = 0; speed += 0.1; }());完整代碼
<!DOCTYPE html><html lang=en><head><meta charset=UTF-8><title>HTML5 Canvas 圓形進度條並顯示數字百分比</title><style>*{margin:0;padding: 0;}body{text-align:center;background-color:#000;}</style></head><body><canvas id=canvas width=500 height=500 style=background:#000;>< /canvas><script> window.onload = function(){ var canvas = document.getElementById('canvas'), //獲取canvas元素context = canvas.getContext('2d'), //獲取畫圖環境，指明為2d centerX = canvas.width/2, //Canvas中心點x軸坐標centerY = canvas.height/2, //Canvas中心點y軸坐標rad = Math.PI*2/100, //將360度分成100份，那麼每一份就是rad度speed = 0.1; //加載的快慢就靠它了//繪製5像素寬的運動外圈function blueCircle(n){ context.save(); context.strokeStyle = #fff ; //設置描邊樣式context.lineWidth = 5; //設置線寬context.beginPath(); //路徑開始context.arc(centerX, centerY, 100 , -Math.PI/2, -Math.PI/ 2 +n*rad, false); //用於繪製圓弧context.arc(x坐標，y坐標，半徑，起始角度，終止角度，順時針/逆時針) context.stroke(); //繪製context.closePath(); //路徑結束context.restore(); } //繪製白色外圈function whiteCircle(){ context.save(); context.beginPath(); context.lineWidth = 2; //設置線寬context.strokeStyle = red; context.arc(centerX, centerY, 100 , 0, Math.PI*2, false); context.stroke(); context.closePath(); context.restore(); } //百分比文字繪製function text(n){ context.save(); //save和restore可以保證樣式屬性只運用於該段canvas元素context.strokeStyle = #fff; //設置描邊樣式context.font = 40px Arial; //設置字體大小和字體//繪製字體，並且指定位置context.strokeText(n.toFixed(0)+%, centerX-25, centerY+10); context.stroke(); //執行繪製context.restore (); } //動畫循環(function drawFrame(){ window.requestAnimationFrame(drawFrame); context.clearRect(0, 0, canvas.width, canvas.height); whiteCircle(); text(speed); blueCircle(speed ); if(speed > 100) speed = 0; speed += 0.1; }()); }</script></body></html>以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VeVb武林網。