H5 Canvas makes a circular progress bar and displays a numerical percentage

This time I will bring you the H5 Canvas to make a circular shapeProgress barand display the numerical percentage. Canvas to make a circular progress bar and display the numerical percentageNotesYes Which ones, the following are practical cases, let’s take a look.

This article introduces an example of the effect of implementing a circular progress bar and displaying a numerical percentage in HTML5 Canvas, as follows:

Implementation effect

1 .First create html code

<canvas id="canvas" width="500" height="500" style="background:#000;"></canvas>

2.Create canvasEnvironment

var canvas = document.getElementById('canvas'),  //获取canvas元素
            context = canvas.getContext('2d'),  //获取画图环境，指明为2d
            centerX = canvas.width/2,   //Canvas中心点x轴坐标
            centerY = canvas.height/2,  //Canvas中心点y轴坐标
            rad = Math.PI*2/100, //将360度分成100份，那么每一份就是rad度
            speed = 0.1; //加载的快慢就靠它了

3.Draw a 5 pixel wide movement outer circle

//绘制5像素宽的运动外圈
        function blueCircle(n){
            context.save();
            context.strokeStyle = "#fff"; //设置描边样式
            context.lineWidth = 5; //设置线宽
            context.beginPath(); //路径开始
            context.arc(centerX, centerY, 100 , -Math.PI/2, -Math.PI/2 +n*rad, false); //用于绘制圆弧context.arc(x坐标，y坐标，半径，起始角度，终止角度，顺时针/逆时针)
            context.stroke(); //绘制
            context.closePath(); //路径结束
            context.restore();
        }

4.Draw White outer ring

//绘制白色外圈
        function whiteCircle(){
            context.save();
            context.beginPath();
            context.lineWidth = 2; //设置线宽
            context.strokeStyle = "red";
            context.arc(centerX, centerY, 100 , 0, Math.PI*2, false);
            context.stroke();
            context.closePath();
            context.restore();
        }

5. Percentage text drawing

function text(n){
            context.save(); //save和restore可以保证样式属性只运用于该段canvas元素
            context.strokeStyle = "#fff"; //设置描边样式
            context.font = "40px Arial"; //设置字体大小和字体
            //绘制字体，并且指定位置
            context.strokeText(n.toFixed(0)+"%", centerX-25, centerY+10);
            context.stroke(); //执行绘制
            context.restore();
        }

6. Make it move

//动画循环
        (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;
        }());

Complete code

<canvas id="canvas" width="500" height="500" style="background:#000;"></canvas>
<script>
    window.onload = function(){
        var canvas = document.getElementById('canvas'),  //获取canvas元素
            context = canvas.getContext('2d'),  //获取画图环境，指明为2d
            centerX = canvas.width/2,   //Canvas中心点x轴坐标
            centerY = canvas.height/2,  //Canvas中心点y轴坐标
            rad = Math.PI*2/100, //将360度分成100份，那么每一份就是rad度
            speed = 0.1; //加载的快慢就靠它了 
            
        //绘制5像素宽的运动外圈
        function blueCircle(n){
            context.save();
            context.strokeStyle = &quot;#fff&quot;; //设置描边样式
            context.lineWidth = 5; //设置线宽
            context.beginPath(); //路径开始
            context.arc(centerX, centerY, 100 , -Math.PI/2, -Math.PI/2 +n*rad, false); //用于绘制圆弧context.arc(x坐标，y坐标，半径，起始角度，终止角度，顺时针/逆时针)
            context.stroke(); //绘制
            context.closePath(); //路径结束
            context.restore();
        }
        //绘制白色外圈
        function whiteCircle(){
            context.save();
            context.beginPath();
            context.lineWidth = 2; //设置线宽
            context.strokeStyle = &quot;red&quot;;
            context.arc(centerX, centerY, 100 , 0, Math.PI*2, false);
            context.stroke();
            context.closePath();
            context.restore();
        }  
        //百分比文字绘制
        function text(n){
            context.save(); //save和restore可以保证样式属性只运用于该段canvas元素
            context.strokeStyle = &quot;#fff&quot;; //设置描边样式
            context.font = &quot;40px Arial&quot;; //设置字体大小和字体
            //绘制字体，并且指定位置
            context.strokeText(n.toFixed(0)+&quot;%&quot;, centerX-25, centerY+10);
            context.stroke(); //执行绘制
            context.restore();
        } 
        //动画循环
        (function drawFrame(){
            window.requestAnimationFrame(drawFrame);
            context.clearRect(0, 0, canvas.width, canvas.height);
            whiteCircle();
            text(speed);
            blueCircle(speed);
            if(speed &gt; 100) speed = 0;
            speed += 0.1;
        }());
    }
</script>

I believe you will read the case in this article You have mastered the method. For more exciting information, please pay attention to other related articles on the php Chinese website!

Recommended reading:

Canvas implements the drawing of rotating windmills

data-*interaction with js

The above is the detailed content of H5 Canvas makes a circular progress bar and displays a numerical percentage. For more information, please follow other related articles on the PHP Chinese website!