iOS AVPlayer 音乐播放器使用注意事项

关于音乐播放总时长的获取

• 官方解说如下

/**
     @property duration
     @abstract Indicates the duration of the item, not considering either its forwardPlaybackEndTime or reversePlaybackEndTime.
     
     @discussion
    	This property is observable. The duration of an item can change dynamically during playback.
    	
    	Unless you omit @"duration" from the array of asset keys you pass to +playerItemWithAsset:automaticallyLoadedAssetKeys: or
    	-initWithAsset:automaticallyLoadedAssetKeys:, the value of this property will accord with the properties of the underlying
    	AVAsset and the current state of playback once the receiver becomes ready to play.
    
    	Before the underlying duration has been loaded, the value of this property is kCMTimeIndefinite. Use key-value observation to
    	obtain a valid duration as soon as it becomes available. (Note that the value of duration may remain kCMTimeIndefinite,
    	e.g. for live streams.)
     */
    @available(iOS 4.3, *)
    open var duration: CMTime { get }

• 意思是要是想获取这个属性,AVPlayerItem必须使用这种初始化方式否则获取的都是nan

let asset = AVAsset.init(url: l)
 print("总时长 \(asset.duration)")
            
let item = AVPlayerItem.init(asset: asset, automaticallyLoadedAssetKeys: ["\(asset.duration)"])