//首先创建一个innerAudioContext对象
let innerAudioContext = uni.createInnerAudioContext({
	useWebAudioImplement: true
})
innerAudioContext.src = encodeURI(this.audio)
innerAudioContext.autoplay = true //设置自动播放
innerAudioContext.volume = 0  //设置播放音量为0
innerAudioContext.startTime = 0
innerAudioContext.play();  //手动播放音频
const getDuration = () => {
	setTimeout(() => {
		if (innerAudioContext.duration === 0) {
			getDuration();
		} else {
			// 获取到正确的duration
			this.duration = innerAudioContext.duration;
                        //手动停止播放，并且销毁innerAudioContext对象
			innerAudioContext.stop();
			innerAudioContext.src = "";
			innerAudioContext.autoplay = false;
			innerAudioContext.destroy();
		}
	}, 100);
}
innerAudioContext.onPlay(getDuration);  //音频播放的时候调用获取音频长度的函数，onCanPlay有时候获取不到duration

//之后再创建新的innerAudioContext对象，正常播放音频