微信小程序转盘抽奖的逻辑原理是：用户点击转盘，程序随机生成一个中奖结果，然后将结果返回给用户。具体实现方式是：使用canvas绘制转盘，将转盘分成多个扇形区域，每个扇形区域对应一个奖品。当用户点击转盘时，程序随机生成一个中奖结果，然后计算出中奖扇形区域的角度范围，最后使用canvas动画将转盘旋转到中奖扇形区域的位置。

以下是微信小程序转盘抽奖的源码示例：

wxml代码：

讯享网

<canvas canvas-id="myCanvas" style="width: 100%; height: 100%;"></canvas> 

js代码：

讯享网Page({ data: { canvasWidth: 0, canvasHeight: 0, ctx: null, prizeList: ['一等奖', '二等奖', '三等奖', '谢谢参与'], prizeColors: ['#FFD700', '#FFA500', '#FFC0CB', '#FFFFFF'], prizeAngles: [], startAngle: 0, endAngle: 0, isRunning: false, prizeIndex: -1, }, onLoad: function () { var that = this; wx.getSystemInfo({ success: function (res) { that.setData({ canvasWidth: res.windowWidth, canvasHeight: res.windowHeight, }); }, }); }, onReady: function () { var that = this; var ctx = wx.createCanvasContext('myCanvas'); that.setData({ ctx: ctx, }); that.drawPrize(); }, drawPrize: function () { var that = this; var ctx = that.data.ctx; var canvasWidth = that.data.canvasWidth; var canvasHeight = that.data.canvasHeight; var prizeList = that.data.prizeList; var prizeColors = that.data.prizeColors; var prizeAngles = that.data.prizeAngles; var startAngle = that.data.startAngle; var endAngle = that.data.endAngle; var angle = 2 * Math.PI / prizeList.length; ctx.clearRect(0, 0, canvasWidth, canvasHeight); ctx.translate(canvasWidth / 2, canvasHeight / 2); ctx.rotate(-Math.PI / 2); for (var i = 0; i < prizeList.length; i++) { ctx.beginPath(); ctx.moveTo(0, 0); ctx.arc(0, 0, canvasWidth / 2 - 50, startAngle, endAngle, false); ctx.closePath(); ctx.fillStyle = prizeColors[i]; ctx.fill(); ctx.save(); ctx.rotate(endAngle - angle / 2); ctx.fillStyle = '#000000'; ctx.font = 'bold 20px Arial'; ctx.fillText(prizeList[i], canvasWidth / 3 - 30, 0); ctx.restore(); prizeAngles.push({ startAngle: startAngle, endAngle: endAngle, }); startAngle = endAngle; endAngle += angle; } that.setData({ prizeAngles: prizeAngles, }); }, start: function () { var that = this; var ctx = that.data.ctx; var prizeAngles = that.data.prizeAngles; var isRunning = that.data.isRunning; var prizeIndex = that.data.prizeIndex; if (isRunning) { return; } isRunning = true; prizeIndex = -1; that.setData({ isRunning: isRunning, prizeIndex: prizeIndex, }); var animation = wx.createAnimation({ duration: 4000, timingFunction: 'ease', }); animation.rotate(3600).step(); ctx.draw(true); setTimeout(function () { that.setData({ isRunning: false, }); var animationData = animation.export(); var currentAngle = 0; animationData.actions.forEach(function (action) { if (action.method == 'rotate') { currentAngle = action.args[0] % 360; } }); for (var i = 0; i < prizeAngles.length; i++) { if (currentAngle >= prizeAngles[i].startAngle && currentAngle < prizeAngles[i].endAngle) { prizeIndex = i; break; } } that.setData({ prizeIndex: prizeIndex, }); wx.showModal({ title: '恭喜您', content: that.data.prizeList[prizeIndex], showCancel: false, }); }, 4000); }, }); 

以上是微信小程序转盘抽奖的逻辑讲解原理及源码。