Chromecast objectForKey 与 Swift答案

【问题标题】：Chromecast objectForKey with SwiftChromecast objectForKey 与 Swift
【发布时间】：2015-02-16 05:19:15
【问题描述】：

我开始在 iOS 中使用 Google Cast API，并试图让它与 Apple 新的编程语言 Swift 一起使用。我在https://github.com/googlecast/CastVideos-ios 使用Google 示例应用程序作为参考。问题是当它连接到投射设备并到达这里时..

func deviceManager(deviceManager: GCKDeviceManager!, didConnectToCastApplication applicationMetadata: GCKApplicationMetadata!, sessionID: String!, launchedApplication: Bool) {
    NSLog("application has launched \(launchedApplication)")

    mediaControlChannel = GCKMediaControlChannel.alloc()
    mediaControlChannel.delegate = self
    self.deviceManager.addChannel(mediaControlChannel)
    mediaControlChannel.requestStatus()
    NSLog("waarde van requestStatus is: \(mediaControlChannel.requestStatus())")
}

它启动并且 NSLog 给了我这个 “应用程序已启动：false” 然后我收到以下错误.. “由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因: 'setObjectForKey: key cannot be nil'" 我查看了 Google Cast iOS 类文档，发现了这个https://developers.google.com/cast/docs/reference/ios/interface_g_c_k_media_metadata

然后我在那个班级里发现了这个

- (id) objectForKey:     (NSString *)   key 
Reads the value of a field.

所以我的想法是我必须在这里放一些东西..

   @IBAction func sendVideo(sender: AnyObject) {
    NSLog("Cast video")

    if deviceManager == nil {
        var alert = UIAlertController(title: "Not connected", message: "Please connect to Cast device", preferredStyle: UIAlertControllerStyle.Alert)
        alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
        presentViewController(alert, animated: true, completion: nil)

        return
    }

    // Define media metadata
    var metaData = GCKMediaMetadata(metadataType: GCKMediaMetadataType.User)
    metaData.setString("Bug Bunny!", forKey: kGCKMetadataKeyTitle)
    metaData.setString("dit is allemaal maar was subtitles dasdsadhjsdfgjkkHDHSAGDH", forKey: kGCKMetadataKeySubtitle)

    var url = NSURL(string: "http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/images/BigBuckBunny.jpg")
    metaData.addImage(GCKImage(URL: url, width: 480, height: 360))

    var mediaInformation = GCKMediaInformation(contentID: "http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/images/BigBuckBunny.jpg", streamType: .None, contentType: "video/mp4", metadata: metaData as GCKMediaMetadata, streamDuration: 0, customData: nil)


    NSLog("waarde van mediainformation is : \(mediaInformation)")

    mediaControlChannel.loadMedia(mediaInformation, autoplay: true, playPosition: 0)
}

【问题讨论】：

使用mediaControlChannel = GCKMediaControlChannel() 而不是mediaControlChannel = GCKMediaControlChannel.alloc()。
@Jesper 我已经尝试过了，当我这样做时，它甚至没有进入函数。它以某种方式跳过了函数..
所以它甚至没有记录第一行？这听起来像是你应该向 Apple 报告的错误。
@Jesper 不，它不会第一次记录它。当我第一次启动应用程序时，我收到一条日志说“已连接”，但没有发生我没有收到“应用程序已启动”的消息。当我重新启动它以使其第二次启动时，我收到消息“应用程序已启动”，然后我按下按钮投射示例视频，然后什么也没有发生。我什至没有收到错误.. 我真的一无所知！
当您在该函数的开头设置断点并单步执行时会发生什么？

标签： ios swift google-cast

【解决方案1】：

正如Jesper 指出的那样，GCKMediaControlChannel.alloc() 行是错误的。

这是一个我知道有效的 Swift 移植 didConnectToCastApplication 方法（来自 Google CastVideos-ios 示例）：

func deviceManager(deviceManager: GCKDeviceManager!, didConnectToCastApplication applicationMetadata: GCKApplicationMetadata!, sessionID: String!, launchedApplication: Bool) {

    self.isReconnecting = false
    self.mediaControlChannel = GCKMediaControlChannel()
    self.mediaControlChannel?.delegate = self
    self.receiverCommandChannel = ChromecastCommandChannel()
    self.receiverCommandChannel?.delegate = self

    self.deviceManager?.addChannel(self.mediaControlChannel)
    self.deviceManager?.addChannel(self.receiverCommandChannel)
    self.mediaControlChannel?.requestStatus()
    self.receiverCommandChannel?.requestStatus()

    self.applicationMetadata = applicationMetadata
    self.updateCastIconButtonStates()

    if let delegate = self.delegate {
        if let device = self.selectedDevice {
            delegate.didConnectToDevice(device)
        } else {
            NSLog("Can not connect to device as no selected device is set")
        }
    } else {
        NSLog("Can not run didConnectToDevice as delegate is not set")
    }

    // Store sessionId in case of restart
    let defaults = NSUserDefaults.standardUserDefaults()
    defaults.setObject(sessionID, forKey: "lastCCSessionId")
    if let deviceId = self.selectedDevice?.deviceID {
        defaults.setObject(deviceId, forKey: "lastCCDeviceId")
    }
    defaults.synchronize()
}

【讨论】：