Page({     onReady() {         this.videoCtx = wx.createVideoContext('myVideo')     },     bindSendDanmu: function () {         this.videoContext.sendDanmu({             text: this.inputValue,             color: getRandomColor()         })     } }) 一旦我点击发送弹幕按钮就报错： thirdScriptError     Cannot read property 'sendDanmu' of undefined;at pages/cover-view/cover-view page bindSendDanmu function     TypeError: Cannot read property 'sendDanmu' of undefined 如果使用 wx.createVideoContext('myVideo').sendDanmu({}) 就没问题 WXML： [图片]