苹果手机，BackgroundAudioManager第二次设置src属性时，如果不是在onEnd的回调函数中设置src，会立即触发 onStop ，

const backgroundAudioManager = wx.getBackgroundAudioManager();
backgroundAudioManager.title = `music`;
backgroundAudioManager.src = 'https://www.xxx.com/aaa.mp3';
backgroundAudioManager.src = 'https://www.xxx.com/aaa.mp3';   // 第二次设置src会立即触发 onStop回调