為您的 iOS 應用程式新增進階功能

廣告插播

iOS 傳送端 SDK 支援特定媒體串流中的廣告插播和隨播廣告。

如要進一步瞭解廣告插播的運作方式，請參閱「Web Receiver 廣告插播總覽」。

雖然可以在傳送端和接收端指定中斷點，但建議在 Web Receiver 和 Android TV Receiver 上指定中斷點，確保各平台行為一致。

在 iOS 上，使用 GCKAdBreakClipInfo 和 GCKAdBreakInfo 在載入指令中指定廣告插播：

Swift
let breakClip1Builder = GCKAdBreakClipInfoBuilder(adBreakClipID: "bc0")
breakClip1Builder.title = "Clip title"
if let posterUrl = URL(string: "https://www.some.url") {
  breakClip1Builder.posterURL = posterUrl
}
breakClip1Builder.duration = 60
breakClip1Builder.whenSkippable = 5  // Set this field so that the ad is skippable
let breakClip1 = breakClip1Builder.build()

let breakClip2 = ...
let breakClip3 = ...


let break1 = GCKAdBreakInfoBuilder(adBreakID: "b0", adBreakClipIds: ["bc0", "bc1", "bc2"]).build()
let mediaInfoBuilder = GCKMediaInformationBuilder(entity: "entity")
...
mediaInfoBuilder.adBreaks = [break1]
mediaInfoBuilder.adBreakClips = [breakClip1, breakClip2, breakClip3]
...
mediaInformation = mediaInfoBuilder.build()

let mediaLoadRequestDataBuilder = GCKMediaLoadRequestDataBuilder()
mediaLoadRequestDataBuilder.mediaInformation = mediaInformation

sessionManager.currentSession?.remoteMediaClient?.loadMedia(with: mediaLoadRequestDataBuilder.build())
Objective-C
GCKAdBreakClipInfoBuilder *breakClipInfoBuilder = [[GCKAdBreakClipInfoBuilder alloc] initWithAdBreakClipID:@"bc0"];
breakClipInfoBuilder.title = @"Clip title";
breakClipInfoBuilder.posterURL = [[NSURL alloc] initWithString:@"https://www.some.url"];
breakClipInfoBuilder.duration = 60;
breakClipInfoBuilder.whenSkippable = 5;
GCKAdBreakClipInfo *breakClip1 = breakClipInfoBuilder.build;

GCKAdBreakClipInfo *breakClip2 = ...
GCKAdBreakClipInfo *breakClip3 = ...

GCKAdBreakInfo *break1 = [[GCKAdBreakInfoBuilder alloc] initWithAdBreakID:@"b0"
                                                           adBreakClipIds:@[@"bc0", @"bc1", @"bc2"]].build;

GCKMediaInformationBuilder *mediaInfoBuilder = [[GCKMediaInformationBuilder alloc]
                                                initWithEntity:@"entity"];
...
mediaInfoBuilder.adBreaks = @[break1];
mediaInfoBuilder.adBreakClips = @[breakClip1, breakClip2, breakClip3];
...
self.mediaInformation = [mediaInfoBuilder build];

GCKMediaLoadRequestDataBuilder *mediaLoadRequestDataBuilder = [[GCKMediaLoadRequestDataBuilder alloc] init];
mediaLoadRequestDataBuilder.mediaInformation = self.mediaInformation;

// Send a load request to the remote media client.
GCKRequest *request = [self.sessionManager.currentSession.remoteMediaClient
                                loadMediaWithLoadRequestData:[mediaLoadRequestDataBuilder build]];

變速播放

應用程式可以顯示及變更目前媒體項目的播放速率。 您可以使用 GCKRemoteMediaClient 的 -[setPlaybackRate:] 或 -[setPlaybackRate:customData:] 設定速率，使用 GCKUIMediaController 的 playbackRateController 存取 GCKUIPlaybackRateController，並使用 GCKUIPlaybackRateController 的 playbackRate 顯示目前的播放速率。

程式碼範例

下列兩個檔案會實作 GCKUIPlaybackRateController，透過包含「正常」、「半速」和「雙倍速度」按鈕的分段控制項，控制播放速率：

Swift
import GoogleCast

/**
 * An implementation of GCKUIPlaybackRateController that controls playback rate
 * using a segmented control that has "normal", "half speed", and "double speed"
 * buttons.
 */
class SegmentedButtonPlaybackRateController: GCKUIPlaybackRateController {
  static let kSegmentNormal = 0;
  static let kSegmentHalfSpeed = 1;
  static let kSegmentDoubleSpeed = 2;

  var segmentedControl: UISegmentedControl!

  override var playbackRate: Float {
    didSet {
      var buttonIndex = 0

      // Map the playback rate to one of our three supported speeds.
      if playbackRate == 1.0 {
        buttonIndex = SegmentedButtonPlaybackRateController.kSegmentNormal
      } else if playbackRate < 1.0 {
        buttonIndex = SegmentedButtonPlaybackRateController.kSegmentHalfSpeed
      } else {
        buttonIndex = SegmentedButtonPlaybackRateController.kSegmentDoubleSpeed
      }

      segmentedControl?.selectedSegmentIndex = buttonIndex
    }
  }
  override var inputEnabled: Bool {
    didSet {
      segmentedControl?.isEnabled = inputEnabled
    }
  }

  /**
   * Designated initializer.
   *
   * @param segmentedControl The segmented control for changing/displaying the
   * playback rate.
   */
  convenience init(_ segmentedControl: UISegmentedControl) {
    self.init()
    self.segmentedControl = segmentedControl;

    segmentedControl.addTarget(self,
                               action: #selector(segmentedControlTapped(sender:)),
                               for: UIControl.Event.valueChanged)
  }

  @objc func segmentedControlTapped(sender: UISegmentedControl) {
    var playbackRate: Float = 1.0

    switch segmentedControl?.selectedSegmentIndex {
    case SegmentedButtonPlaybackRateController.kSegmentHalfSpeed:
      playbackRate = 0.5;
    case SegmentedButtonPlaybackRateController.kSegmentDoubleSpeed:
      playbackRate = 2.0;
    case SegmentedButtonPlaybackRateController.kSegmentNormal:
      fallthrough
    default:
      playbackRate = 1.0;
    }

    self.playbackRate = playbackRate
  }
}
Objective-C

SegmentedButtonPlaybackRateController.h

#import <GoogleCast/GoogleCast.h>
#import <UIKit/UIKit.h>

/**
 * An implementation of GCKUIPlaybackRateController that controls playback rate
 * using a segmented control that has "normal", "half speed", and "double speed"
 * buttons.
 */
@interface SegmentedButtonPlaybackRateController : GCKUIPlaybackRateController

/**
 * Designated initializer.
 *
 * @param segmentedControl The segmented control for changing/displaying the
 * playback rate.
 */
- (instancetype)initWithSegmentedControl:(UISegmentedControl *)segmentedControl;

@end

SegmentedButtonPlaybackRateController.m

#import "SegmentedButtonPlaybackRateController.h"

@interface SegmentedButtonPlaybackRateController () {
  UISegmentedControl *_segmentedControl;
}

@end

static const NSInteger kSegmentNormal = 0;
static const NSInteger kSegmentHalfSpeed = 1;
static const NSInteger kSegmentDoubleSpeed = 2;

@implementation SegmentedButtonPlaybackRateController

- (instancetype)initWithSegmentedControl:(UISegmentedControl *)segmentedControl {
  if (self = [super init]) {
    _segmentedControl = segmentedControl;
    [_segmentedControl addTarget:self
                          action:@selector(segmentedControlTapped:)
                forControlEvents:UIControlEventValueChanged];
  }
  return self;
}

- (void)setPlaybackRate:(float)playbackRate {
  [super setPlaybackRate:playbackRate];

  NSInteger buttonIndex = 0;

  // Map the playback rate to one of our three supported speeds.
  if (playbackRate == 1.0) {
    buttonIndex = kSegmentNormal;
  } else if (playbackRate < 1.0) {
    buttonIndex = kSegmentHalfSpeed;
  } else {
    buttonIndex = kSegmentDoubleSpeed;
  }

  _segmentedControl.selectedSegmentIndex = buttonIndex;
}

- (void)setInputEnabled:(BOOL)inputEnabled {
  _segmentedControl.enabled = inputEnabled;
  [super setInputEnabled:inputEnabled];
}

- (void)segmentedControlTapped:(id)sender {
  float playbackRate;

  switch (_segmentedControl.selectedSegmentIndex) {
    case kSegmentHalfSpeed:
      playbackRate = 0.5;
      break;

    case kSegmentDoubleSpeed:
      playbackRate = 2.0;
      break;

    case kSegmentNormal:
    default:
      playbackRate = 1.0;
      break;
  }

  self.playbackRate = playbackRate;
}

@end

新增自訂管道

Cast 架構提供兩種建立管道的方式，可將自訂訊息傳送至網頁接收器：

  1. GCKCastChannel 應為子類別，用於實作具有相關聯狀態的非簡單管道。
  2. GCKGenericChannel 可做為子類別的替代方案，它會將收到的訊息傳遞至委派項目，以便在其他位置處理。

以下是 GCKCastChannel 的導入範例：

Swift
class HGCTextChannel: GCKCastChannel {
  override func didReceiveTextMessage(_ message: String) {
    print("received message: \(message)")
  }
}
Objective-C

HGCTextChannel.h

#import <GoogleCast/GCKCastChannel.h>

@interface HGCTextChannel : GCKCastChannel

@end

HGCTextChannel.m

#import "HGCTextChannel.h"

@implementation HGCTextChannel
- (void)didReceiveTextMessage:(NSString*)message {
  NSLog(@"received message: %@", message);
}

@end

隨時可以註冊頻道；如果工作階段目前未處於連線狀態，只要工作階段連線，頻道就會自動連線，前提是頻道命名空間必須位於 Web Receiver 應用程式中支援的命名空間清單。

每個自訂管道都由專屬命名空間定義，且必須以 urn:x-cast: 前置字元開頭，例如 urn:x-cast:com.example.custom。您可以建立多個自訂管道，每個管道都有專屬命名空間。Web Receiver 應用程式也可以使用相同的命名空間傳送及接收訊息。

Swift
var error: GCKError?
let textChannel = HGCTextChannel.init(namespace: "urn:x-cast:com.google.cast.sample.helloworld")
sessionManager.currentCastSession?.add(textChannel)
textChannel.sendTextMessage("Hello World", error: &error)

if error != nil {
  print("Error sending text message \(error.debugDescription)")
}
Objective-C
NSError *error;
HGCTextChannel *textChannel = [[HGCTextChannel alloc] initWithNamespace:@"urn:x-cast:com.google.cast.sample.helloworld"];
[sessionManager.currentCastSession addChannel:textChannel];
[textChannel sendTextMessage:@"Hello World"
                       error:&error];

if (error != nil) {
  NSLog(@"Error sending text message: %@", error);
}

如要提供特定管道連線或中斷連線時需要執行的邏輯，請在使用 GCKCastChannel 時覆寫 -[didConnect] 和 -[didDisconnect] 方法，或在使用 GCKGenericChannel 時，為 GCKGenericChannelDelegate 的 -[castChannelDidConnect:] 和 -[castChannelDidDisconnect:] 方法提供實作項目。

支援自動播放

請參閱自動播放和佇列 API。

覆寫圖片選取和快取

架構的各種元件 (包括 Cast 對話方塊、迷你控制器、擴展控制器和 GCKUIMediaController (如有設定)) 會顯示目前投放媒體的圖片。圖片藝術作品的網址通常會包含在媒體的 GCKMediaMetadata 中，但傳送者應用程式可能有其他網址來源。

GCKUIImagePicker 通訊協定定義了選取適用於特定用途和所需大小的圖片方法。這個介面只有一個方法 -[getImageWithHints:fromMetadata:]，會將 GCKUIImageHints 物件和 GCKMediaMetadata 物件做為參數，並傳回 GCKImage 物件做為結果。架構提供 GCKUIImagePicker 的預設實作，一律會選取 GCKMediaMetadata 物件圖片清單中的第一張圖片，但應用程式可以設定 GCKCastContext 單例項的 imagePicker 屬性，提供替代實作。

GCKUIImageCache 通訊協定也定義了快取圖片的方法，這些圖片是由架構使用 HTTPS 下載。架構提供 GCKUIImageCache 的預設實作項目，可將下載的圖片檔案儲存在應用程式的快取目錄中，但應用程式可以透過設定 GCKCastContext 單例項的 imageCache 屬性，提供替代實作項目。

後續步驟

您已瞭解如何將功能新增至 iOS 傳送端應用程式。 現在可以為其他平台 (Android 或 Web) 建構傳送端應用程式， 或建構 Web 接收器。

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