wx.backgroundAudioManager 为什么赋值不成功 无法自动播放呢？

const backgroundAudioManager = wx.getBackgroundAudioManager()

backgroundAudioManager.title = '此时此刻'

backgroundAudioManager.epname = '此时此刻'

backgroundAudioManager.singer = '许巍'

backgroundAudioManager.coverImgUrl = 'http://hqhh.hqhh520.com/GWW-testImg/img0/page1-1.png'

// 设置了 src 之后会自动播放

backgroundAudioManager.src = 'http://hqhh.hqhh520.com/GWW-testImg/media/1.mp3'

console.log(backgroundAudioManager)