微信小程序前端自定义分享的实现方法

 /**
 * 用户点击右上角分享
 */
 onShareAppMessage: function() {
 return {
 imageUrl:'',
 title:''
 };
 }

<canvas canvas-id="canvasid" style="width: 375px; height: 500px;" wx:if="{{canvasShow}}"></canvas>

 let context = wx.createCanvasContext('canvasid')
 context.drawImage(back.path, 0, 60, backWidth, backHeight) //绘制下方背景图
 //绘制圆形头像，参考教程：https://www.jianshu.com/p/9a6ee28d6f 第二种方法

 context.save();
 var d = 2 * 25;
 var cx = 0 + 25;
 var cy = 0 + 25;
 context.arc(cx, cy,25, 0, 2 * Math.PI);
 context.clip();
 context.drawImage(avatar.path, 0,0, d, d);
 context.restore();
 //绘制名字和点赞数
 context.setFontSize(14)
 context.fillText('userName', 70, 32)
 let zanLength = ('100' + '次赞').length
 context.fillText('100'+ '次赞', 375 - 14 * zanLength, 32)
 //执行draw进行渲染 并返回图片url
 context.draw(true, () => {
 //此方法应执行在draw的回调中
 wx.canvasToTempFilePath({
 x: 0,
 y: 0,
 width: 375,
 height: 400,
 destWidth: 375,
 destHeight: 400,
 canvasId: 'canvasid',
 success(res) {
 //设置onShareAppMessage所返回的数据格式
 let shareInfo = {
 title: 'customTitle',
 imageUrl
 }
 //隐藏画布
 that.setData({
 canvasShow: false
 })
 }
 })
 });

 wx.getImageInfo({
 src: imgUrl,
 success: function(res) {
 /**拿到返回值res[0].path,再把该值作为canvas绘制图片的路径 
 context.drawImage(res[0].path,x,x,x)**/
 let drawImgUrl = res[0].path
 }
 });