微信小程序實現幸運大轉盤功能的示例代碼

 getLottery: function () {
    var that = this
    var awardIndex = Math.random() * 6 >>> 0;

    // 獲取獎品配置
    var awardsConfig = app.awardsConfig,
        runNum = 8
    if (awardIndex < 2) awardsConfig.chance = false
    console.log(awardIndex)



    // 旋轉抽獎
    app.runDegs = app.runDegs || 0
    console.log('deg', app.runDegs)
    app.runDegs = app.runDegs + (360 - app.runDegs % 360) + (360 * runNum - awardIndex * (360 / 6))
    console.log('deg', app.runDegs)

    var animationRun = wx.createAnimation({
      duration: 4000,
      timingFunction: 'ease'
    })
    that.animationRun = animationRun
    animationRun.rotate(app.runDegs).step()
    that.setData({
      animationData: animationRun.export(),
      btnDisabled: 'disabled'
    })

   // 繪制轉盤
    var awardsConfig = app.awardsConfig.awards,
        len = awardsConfig.length,
        rotateDeg = 360 / len / 2 + 90,
        html = [],
        turnNum = 1 / len  // 文字旋轉 turn 值
    that.setData({
      btnDisabled: app.awardsConfig.chance ? '' : 'disabled'  
    })
    var ctx = wx.createContext()
    for (var i = 0; i < len; i++) {
      // 保存當前狀態
      ctx.save();
      // 開始一條新路徑
      ctx.beginPath();
      // 位移到圓心，下面需要圍繞圓心旋轉
      ctx.translate(150, 150);
      // 從(0, 0)坐標開始定義一條新的子路徑
      ctx.moveTo(0, 0);
      // 旋轉弧度,需將角度轉換為弧度,使用 degrees * Math.PI/180 公式進行計算。
      ctx.rotate((360 / len * i - rotateDeg) * Math.PI/180);
      // 繪制圓弧
      ctx.arc(0, 0, 150, 0,  2 * Math.PI / len, false);

      // 顏色間隔
      if (i % 2 == 0) {
          ctx.setFillStyle('rgba(255,184,32,.1)');
      }else{
          ctx.setFillStyle('rgba(255,203,63,.1)');
      }

      // 填充扇形
      ctx.fill();
      // 繪制邊框
      ctx.setLineWidth(0.5);
      ctx.setStrokeStyle('rgba(228,55,14,.1)');
      ctx.stroke();

      // 恢復前一個狀態
      ctx.restore();

      // 獎項列表
      html.push({turn: i * turnNum + 'turn', lineTurn: i * turnNum + turnNum / 2 + 'turn', award: awardsConfig[i].name});    
    }

<view class="top">
	<image class="userinfo-avatar" src="{{head}}" background-size="cover"></image>
	<text style="font-size:40rpx">失散多年的哥哥</text>
</view>

<view class="mid">
	<button bindtap="gotoLottery" type="primary" style="width:600rpx;background-color:#D75858">去抽獎</button>
</view>

<view class="txt">
	<text wx:if="{{awardsList.length > 0}}">恭喜您獲得瞭以下獎品：</text>
	<text wx:if="{{awardsList.length == 0}}">您還中獎，快去抽獎吧</text>
</view>

<view class="gift" wx:for="{{awardsList}}" wx:key="unique">
	<text style="font-size:34rpx;margin-left:30rpx">{{item}}</text>
</view>