问iOS AVPlayerLayer不播放本地视频

EN

import UIKit
import CoreGraphics
import AVFoundation
import XCPlayground
XCPExecutionShouldContinueIndefinitely()

var url = NSURL(string: "/Users/MyUsername/Desktop/Video.mp4")
//var url = NSURL(string: "http://download.wavetlan.com/SVV/Media/HTTP/MP4/ConvertedFiles/MediaCoder/MediaCoder_test2_1m10s_XVID_VBR_131kbps_480x320_25fps_AACLCv4_VBR_32kbps_Stereo_24000Hz.mp4")
println(url.absoluteString)

var exists = NSFileManager.defaultManager().fileExistsAtPath(url.absoluteString)
println(exists ? "true" : "false")

var playerAsset = AVURLAsset(URL: url, options: nil)
playerAsset.loadValuesAsynchronouslyForKeys(
    ["duration"],
    completionHandler: {
        var error: NSError?
        switch playerAsset.statusOfValueForKey("duration", error: &error) {
        case AVKeyValueStatus.Loaded:
            println("Duration: \(playerAsset.duration)")
        default:
            println("Failed duration")
        }
    })

var playerItem = AVPlayerItem(asset: playerAsset)

var player =  AVPlayer(playerItem: playerItem)

var movieLayer = AVPlayerLayer(player: player)

movieLayer.backgroundColor = UIColor.redColor().CGColor
movieLayer.frame = CGRect(x: 25, y: 25, width: 100, height: 100)
movieLayer.opacity = 1.0

player.play()

var view = UIView(frame: CGRect(x: 0, y: 0, width: 150, height: 150))
view.layer.addSublayer(movieLayer)

XCPShowView("Movie View", view)