微信小程序 纯css画仪表盘

刚看到设计稿的时候第一时间想到的就是用canvas来做这个仪表盘，虽然本人的画布用的不是很好但还可以写一写。话不多说直接上代码。最后有纯css方法

<canvas canvas-id="circle" class="circle" >

// js
data: {
    canvasWidth: 285, // 画布宽度
    canvasHeight: 285, // 画布高度
    value: 60, // 当前得分
},

  /*
   * 绘制仪表盘
   */
  showCanvasRing() {
    var that = this;
    var ctx = wx.createCanvasContext("circle");
    ctx.clearRect(0, 0, that.data.canvasWidth, that.data.canvasHeight); // 清除画布
    var circle_r = that.data.canvasWidth / 2; //画布的一半，用来找中心点和半径
    var scoreText = that.data.value>=100?100:that.data.value; // 当前得分 最多100分
    var descript = '良好'; // 当前描述
    var date = formatTime(new Date(),'MM-DD'); // 当前日期
    // 圆弧起点
    var startAngle = 0.8 * Math.PI;
    var endAngle = 2.2 * Math.PI;
    //定义起始点
    ctx.translate(that.data.canvasWidth / 2, that.data.canvasHeight / 2);
    // 画圆背景
    ctx.beginPath();
    ctx.setStrokeStyle("#6bb7b9");
    ctx.fillStyle="#6bb7b9";
    ctx.setLineCap("round");
    ctx.arc(0, 0, circle_r,2*Math.PI);
    ctx.fill()
    ctx.stroke();
    ctx.closePath();

    //  白半边圆弧
    ctx.beginPath();
    ctx.setStrokeStyle("#FFFFFF");
    ctx.setLineWidth(10);
    ctx.setLineCap("round");
    ctx.arc(0, 0, circle_r - 20, startAngle, endAngle, false);
    ctx.stroke();
    ctx.closePath();

    // 刻度
    for (let i = 0; i <= 10; i++) {
      let angle = startAngle + (endAngle - startAngle - 0.1) * (i * 10) / 100;
      if (angle > Math.PI * 2) {
        angle = angle - Math.PI * 2
      }
      const point = that.getPoint(0, 0, circle_r - 44, angle);
      const PI_3_2 = Math.PI * 1.5;
      const PI_1_2 = Math.PI * 0.5;
      ctx.save()
      ctx.setFillStyle("#fff");
      ctx.setFontSize(13);
      ctx.translate(point.x, point.y)
      const rotateDegrees = angle >= PI_3_2 ? (angle - PI_3_2) : (angle + PI_1_2);
      ctx.rotate(rotateDegrees)
      ctx.fillText(i * 10, 0, 0)
      ctx.restore()
    }

    // 当前得分内圆弧
    ctx.beginPath();
    ctx.setStrokeStyle("#FFA64D");
    ctx.setLineWidth(10);
    ctx.setLineCap("round");
    ctx.arc(0, 0, circle_r - 20, startAngle, startAngle + (endAngle - startAngle) * scoreText / 100, false);
    ctx.stroke();
    ctx.closePath();


    // 分数
    ctx.setTextAlign("center"); // 字体位置
    ctx.setFillStyle("#fff");
    ctx.font = "900 50px Arial"
    ctx.fillText(scoreText, 0, -20);

    // 描述
    ctx.setTextAlign("center"); // 字体位置
    ctx.font = "400 15px Arial"
    ctx.fillText(descript, 0, 15);

    // 日期
    ctx.setTextAlign("center");
    ctx.setLineWidth(8);
    ctx.setFontSize(14);
    ctx.fillText(date + ' 更新', 0, 35);

    // 绘图
    ctx.draw();
  },
  getPoint: function (x, y, r, angle) {
    const x1 = x + r * Math.cos(angle);
    const y1 = y + r * Math.sin(angle);
    return {
      x: x1,
      y: y1
    }
  },

到此仪表盘就画完了，最后需求有变动需要再仪表盘上加文本，众所周知canvas在小程序中的层级很高。但是官方说可以使用cover-view | cover-image

 <canvas canvas-id="circle" class="circle" >
 	<cover-view class="lowScore" wx-if="{{showView}}">
      目前信用分过低
    cover-view>
 canvas>

经过验证cover-view可以做到在canvas上悬浮，但是不能满足所有需求；
比如要悬浮scroll-view ，总不能把内容全部用画布来写吧 ~ ~。也有人说可以将绘画完成后的canvas转成图片进行显示wx.canvasToTempFilePath。我同样也试过但是会报错：canvasToTempFilePath:fail fail canvas is empty，怎么解决试了好半天，由于项目着急也没用太多时间研究了。所有最后我决定使用最原始的方法来实现。来看代码吧 ↓ ↓

 
<view class="dashboard">
  <view class="dashboard-arc">
    <view class="dashboard-scale">
      <view wx:for="{{[0,10,20,30,40,50,60,70,80,90,100]}}" wx:key="item">{{item}}view>
    view>
    <view class="dashboard-arc-active" style="background: conic-gradient(#FFA64D 0, #FFA64D {{(value*0.75)}}%, transparent 0, transparent);">
      <view class="dashboard-arc-active-end" style="transform: translateX(-50%) rotate({{(value/100)*270}}deg);">view>
    view>
  view>
  <view class="dashboard-content">
    <view class="dashboard-content-title">{{value}}view>
    <view class="dashboard-content-text">{{state}}view>
    <view class="dashboard-content-desc">{{tool.formatTime(date,'MM-DD')}} 更新view>
  view>
  <view class="lowScore" wx-if="{{showView}}">目前信用分过低view>
...要悬浮的内容
view>

	/* 仪表盘 */
	.dashboard {
	    width: 750rpx;
	    height: 600rpx;
	    background: rgba(70, 165, 168, 1);
	    box-shadow: 0px 10px 20px rgba(0, 0, 0, 0.1);
	    text-align: center;
	    position: relative;
	}
	.dashboard::before{
	  content: '';
	  width: 570rpx;
	  height: 570rpx;
	  position: absolute;
	  top: 50%;
	  left: 50%;
	  transform: translate(-50%, -50%);
	  background-color: #6bb7b9;
	  border-radius: 50%;
	}
	.dashboard-arc{
	  width: 520rpx;
	  height: 520rpx;
	  position: absolute;
	  top: 50%;
	  left: 50%;
	  transform: translate(-50%, -50%);
	  transform: translate(-50%, -50%) rotate(-135deg);
	  border-radius: 50%;
	  background: conic-gradient(#fff 0, #fff 75%, transparent 0, transparent);
	}
	.dashboard-arc::before,
	.dashboard-arc::after{
	  content: "";
	  position: absolute;
	  width: 20rpx;
	  height: 20rpx;
	  border-radius: 50%;
	  background: #fff;
	}
	.dashboard-arc::before{
	  left: 50%;
	  top: 0;
	  background-color: #FFA64D;
	  transform: translateX(-50%);
	}
	.dashboard-arc::after{
	  left: 0;
	  top: 50%;
	  transform: translateY(-50%);
	}
	.dashboard-arc-active{
	  position: absolute;
	  width: 100%;
	  height: 100%;
	  border-radius: 50%;
	  top: 0;
	  left: 0;
	}
	.dashboard-arc-active-end{
	  position: absolute;
	  width: 20rpx;
	  height:100%;
	  top: 0;
	  left: 50%;
	  z-index: 1;
	}
	.dashboard-arc-active-end::before{
	  content: '';
	  width: 20rpx;
	  height: 20rpx;
	  position: absolute;
	  top: 0;
	  left: 0;
	  background: #FFA64D;
	  border-radius: 50%;
	}
	.dashboard-scale{
	  background-color: #6bb7b9;
	  width: 480rpx;
	  height: 480rpx;
	  border-radius: 50%;
	  position: relative;
	  top: 50%;
	  left: 50%;
	  z-index: 99;
	  font-size: 20rpx;
	  transform: translate(-50%, -50%);
	  color: #fff;
	}
	.dashboard-scale>view{
	  position: absolute;
	  top: 50%;
	  height:calc(100% - 10rpx);
	  left: 50%;
	  transform: translate(-50%,-50%);
	}
	.dashboard-scale>view:nth-child(2){
	  transform:translate(-50%,-50%)rotate(27deg);
	}
	.dashboard-scale>view:nth-child(3){
	  transform:translate(-50%,-50%)rotate(54deg);
	}
	.dashboard-scale>view:nth-child(4){
	  transform:translate(-50%,-50%)rotate(81deg);
	}
	.dashboard-scale>view:nth-child(5){
	  transform:translate(-50%,-50%)rotate(108deg);
	}
	.dashboard-scale>view:nth-child(6){
	  transform:translate(-50%,-50%)rotate(135deg);
	}
	.dashboard-scale>view:nth-child(7){
	  transform:translate(-50%,-50%)rotate(162deg);
	}
	.dashboard-scale>view:nth-child(8){
	  transform:translate(-50%,-50%)rotate(189deg);
	}
	.dashboard-scale>view:nth-child(9){
	  transform:translate(-50%,-50%)rotate(216deg);
	}
	.dashboard-scale>view:nth-child(10){
	  transform:translate(-50%,-50%)rotate(243deg);
	}
	.dashboard-scale>view:nth-child(11){
	  transform:translate(-50%,-50%)rotate(270deg);
	}
	.dashboard-content{
	  position: absolute;
	  width: 300rpx;
	  height: 300rpx;
	  top: 50%;
	  left: 50%;
	  transform: translate(-50%, -50%);
	  color: #fff;
	  border-radius: 50%;
	  padding: 20rpx;
	}
	.dashboard-content-title{
	  font-size: 115rpx;
	  font-weight: 900;
	}
	.dashboard-content-text{
	  font-size: 25rpx;
	}
	.dashboard-content-desc{
	  font-size: 20rpx;
	}

以上就是所有代码了，觉得对你有用的话就点个赞吧 ！
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