小程序画圆
建立两个canvas标签，先绘制底层的浅灰色圆圈背景，再绘制上层的红色进度条。
.wxml的代码如下：
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<
view
class
=
"wrap"
>
<
view
class
=
"circle-box"
>
<
canvas
class
=
"circle"
style
=
"width:200px; height:200px;"
canvas-id
=
"canvasArcCir"
>
<
canvas
class
=
"circle"
style
=
"z-index: -5; width:200px; height:200px;"
canvas-id
=
"canvasCircle"
>
<
view
class
=
"draw_btn"
bindtap
=
"drawCircle"
>开始动态绘制
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WXSS代码
特别注意：底层的canvas最好使用。
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page {
width: 100%;
height: 100%;
background-color:
#fff;
}
.circle-box {
text-align: center;
margin-top: 10vw;
}
.circle {
position: absolute;
left: 0;
right: 0;
margin: auto;
}
.draw_btn {
width: 35vw;
position: absolute;
top: 33vw;
right: 0;
left: 0;
margin: auto;
border: 1px
#000 solid;
border-radius: 5vw;
}
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js代码如下：
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//获取应用实例
var
app = getApp()
var
interval;
var
varName;
var
ctx = wx.createCanvasContext(
'canvasArcCir'
);
Page({
data: {
},
drawCircle:
function
() {
clearInterval(varName);
function
drawArc(s, e) {
ctx.setFillStyle(
'white'
);
ctx.clearRect(0, 0, 200, 200);
ctx.draw();
var
x = 100, y = 100, radius = 96;
ctx.setLineWidth(5);
ctx.setStrokeStyle(
'#d81e06'
);
ctx.setLineCap(
'round'
);
ctx.beginPath();
ctx.arc(x, y, radius, s, e,
false
);
ctx.stroke()
ctx.draw()
}
var
step = 1, startAngle = 1.5 * Math.PI, endAngle = 0;
var
animation_interval = 1000, n = 60;
var
animation =
function
() {
if
(step <= n) {
endAngle = step * 2 * Math.PI / n + 1.5 * Math.PI;
drawArc(startAngle, endAngle);
step++;
}
else
{
clearInterval(varName);
}
};
varName = setInterval(animation, animation_interval);
},
onReady:
function
() {
//创建并返回绘图上下文context对象。
var
cxt_arc = wx.createCanvasContext(
'canvasCircle'
);
cxt_arc.setLineWidth(6);
cxt_arc.setStrokeStyle(
'#eaeaea'
);
cxt_arc.setLineCap(
'round'
);
cxt_arc.beginPath();
cxt_arc.arc(100, 100, 96, 0, 2 * Math.PI,
false
);
cxt_arc.stroke();
cxt_arc.draw();
},
onLoad:
function
(options) {
}
})
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注意的要点
1、关于小程序canvas绘制，请观看 微信小程序官方文档绘制
2、开始绘制的路径可以根据 JS代码中的变量startAngle 来选择从哪里开始绘制
圆形进度条的效果图如下：
初始状态
点击中间按钮开始绘制
绘制过程
绘制结束