开发 | 手把手，教你在小程序里做一个圆形进度条

{
"component": true
}

<!-- components/circle/circle.wxml -->
<view class="circle_box" style="width:{{size}}px;height:{{size}}px">
          <canvas class="circle_bg" canvas-id="{{bg}}" style="width:{{size}}px;height:{{size}}px"></canvas> 
          <canvas class="circle_draw" canvas-id="{{draw}}" style="width:{{size}}px;height:{{size}}px"></canvas> 
          <slot></slot> 
</view>

/* components/circle/circle.wxss */
.circle_box,.circle_draw{ position: relative; }
.circle_bg{position: absolute;}
</view>

/* components/circle/circle.js */
Component({
  ……
  methods: {
    drawCircleBg: function (id, x, w) {
      // 设置圆环外面盒子大小 宽高都等于圆环直径
      this.setData({
        size: 2 * x
      });
      // 使用 wx.createContext 获取绘图上下文 ctx  绘制背景圆环
      var ctx = wx.createCanvasContext(id)
      ctx.setLineWidth(w / 2); ctx.setStrokeStyle('#20183b'); ctx.setLineCap('round')
      ctx.beginPath();//开始一个新的路径
      //设置一个原点(x,y)，半径为r的圆的路径到当前路径 此处x=y=r
      ctx.arc(x, x, x - w, 0, 2 * Math.PI, false);
      ctx.stroke();//对当前路径进行描边
      ctx.draw();
    },
    drawCircle: function (id, x, w, step) {
      var context = wx.createCanvasContext(id);
      // 设置渐变
      var gradient = context.createLinearGradient(2 * x, x, 0);
      gradient.addColorStop("0", "#2661DD"); gradient.addColorStop("0.5", "#40ED94"); gradient.addColorStop("1.0", "#5956CC");
      context.setLineWidth(w); context.setStrokeStyle(gradient); context.setLineCap('round')
      context.beginPath();//开始一个新的路径
      // step 从0到2为一周
      context.arc(x, x, x - w, -Math.PI / 2, step * Math.PI - Math.PI / 2, false);
      context.stroke();//对当前路径进行描边
      context.draw()
    },
    _runEvent() {
      //触发自定义组件事件
      this.triggerEvent("runEvent")
    }
  },
  ……
})

{
  "usingComponents": {
    "circle": "/components/circle/circle"
  }
}

<!--index.wxml-->
<view class="container">
    <circle id='circle1'
      bg='circle_bg1'
      draw='circle_draw1'
      bind:runEvent="_runEvent" >
        <!-- 这部分内容将被放置在组件 <slot> 的位置上 -->
        <view class="circle_info" bindtap="changeTime">
             <view class="circle_dot"></view>
             <text class='circle_txt'> {{txt}} </text>
       </view>
    </circle>
</view>

/**index.wxss**/
/*圆环进度条文字*/
.circle_info{
  position: absolute; 
  width: 100%;
  left: 50%;
  top: 50%; 
  transform: translate(-50%,-50%); 
  display: flex;  
  align-items: center;
  justify-content: center
}
.circle_dot{
  width:16rpx;
  height: 16rpx;  
  border-radius: 50%;
  background-color: #fb9126;
} 
.circle_txt{
  padding-left: 10rpx;
  color: #fff;
  font-size: 36rpx; 
  letter-spacing: 2rpx;
}

//index.js
 data: { 
    txt: "正在匹配中..." 
  },
 onReady: function () {
   // 获得circle组件
    this.circle = this.selectComponent("#circle1");
    // 绘制背景圆环
    this.circle.drawCircleBg('circle_bg1', 100, 8)
    // 绘制彩色圆环 
    this.circle.drawCircle('circle_draw1', 100, 8, 2);  
  },

this.circle.drawCircle('circle_draw1', 100, 8, 0.5);

this.circle.drawCircle('circle_draw1', 100, 8, 1);

this.circle.drawCircle('circle_draw1', 100, 8, 2);

  data: { 
    txt: "正在匹配中...",
    count: 0,//计数器，初始值为0
    maxCount: 100, // 绘制一个圆环所需的步骤 
    countTimer: null,//定时器，初始值为null
  },
   countInterval: function () {
    // 设置倒计时 定时器 假设每隔100毫秒 count递增+1，当 count递增到两倍maxCount的时候刚好是一个圆环（ step 从0到2为一周），然后改变txt值并且清除定时器
    this.countTimer = setInterval(() => {   
      if (this.data.count <= 2 * this.data.maxCount) {        
        // 绘制彩色圆环进度条
        this.circle.drawCircle('circle_draw1', 100, 8, this.data.count / this.data.maxCount)
        this.data.count++;
        } else {
        this.setData({
          txt: "匹配成功"
        });
         clearInterval(this.countTimer); 
      }
    }, 100)
  },
 onReady: function () {
   // 获得circle组件
    this.circle = this.selectComponent("#circle1");
    // 绘制背景圆环
    this.circle.drawCircleBg('circle_bg1', 100, 8)
    // 绘制彩色圆环 
    // this.circle.drawCircle('circle_draw1', 100, 8, 2);  
    this.countInterval()
  },

<circle id='circle'
bg='circle_bg'
draw='circle_draw'
bind:runEvent="_runEvent" >
  <view class="circle_text" bindtap="changeTime">
  <text class='circle_time'> {{time}} s</text></view>
</circle>

/*圆环倒计时*/
.circle_text{
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%,-50%);
}
.circle_time{
color: #fff;
font-size: 32rpx;
padding-left: 16rpx;
}

const app = getApp()
Page({
  ……
  stepInterval: function () {
    var n = this.data.num / 2  // 设置倒计时 定时器
    this.stepTimer = setInterval(() => {
      if (this.data.num >= 0) {
        this.data.step = this.data.num / n;
        this.circle.drawCircle('circle_draw', 40, 4, this.data.step)// 绘制彩色圆环进度条
        if ((/(^[1-9]\d*$)/.test(this.data.num / 10))) {
          this.setData({ // 当时间为整数秒的时候 改变时间
            time: this.data.num / 10
          });
        }
        this.data.num--;
      } else {
        this.setData({
          time: 0
        });
      }
    }, 100)
  },
  changeTime: function () {
    clearInterval(this.stepTimer);
    this.setData({
      num: 100
    });
    this.stepInterval() // 重新开启倒计时
    this._runEvent() // 触发自定义组件事件
  },
  ……
})