为 iOS 应用添加高级功能

广告插播时间点

iOS 发送方 SDK 支持在给定媒体串流中投放广告插播和随播广告。

如需详细了解广告插播的运作方式，请参阅网站接收器广告插播概览。

虽然您可以在发送器和接收器上指定广告插播时间点，但建议您在 Web 接收器和 Android TV 接收器上指定这些时间点，以便在各个平台上保持一致的行为。

在 iOS 上，使用 GCKAdBreakClipInfo 和 GCKAdBreakInfo 在加载命令中指定广告插播时间点：

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]];

可变播放速率

您的应用可以显示和更改当前媒体项的播放速率。您可以使用 GCKRemoteMediaClient 的 -[setPlaybackRate:] 或 -[setPlaybackRate:customData:] 设置速率，使用 GCKUIMediaController 的 playbackRateController 访问 GCKUIPlaybackRateController，并使用 GCKUIPlaybackRateController 的 playbackRate 显示当前播放速率。

示例代码

以下两个文件实现了 GCKUIPlaybackRateController，它使用包含“正常”“半速”和“双速”按钮的分段控件来控制播放速度：

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

添加自定义渠道

Cast 框架提供了两种创建用于向 Web 接收器发送自定义消息的通道的方法：

  1. GCKCastChannel 旨在作为子类来实现具有关联状态的非琐碎通道。
  2. GCKGenericChannel 作为子类化方法的替代方案提供；它会将收到的消息传递给代理，以便在其他位置进行处理。

下面是一个 GCKCastChannel 实现示例：

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

您可以随时注册渠道；如果会话目前处于未连接状态，则当会话本身连接时，渠道会自动连接，前提是渠道的命名空间位于 Web Receiver 应用元数据的支持的命名空间列表中。

每个自定义渠道都由一个唯一的命名空间定义，并且必须以前缀 urn:x-cast: 开头，例如 urn:x-cast:com.example.custom。您可以有多个自定义渠道，每个渠道都有一个唯一的命名空间。Web 接收器应用也可以使用相同的命名空间发送和接收消息。

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);
}

如需提供在特定通道连接或断开连接时需要执行的逻辑，请替换 -[didConnect] 和 -[didDisconnect] 方法（如果使用 GCKCastChannel），或者为 GCKGenericChannelDelegate 的 -[castChannelDidConnect:] 和 -[castChannelDidDisconnect:] 方法提供实现（如果使用 GCKGenericChannel）。

支持自动播放

请参阅自动播放和队列 API。

替换图片选择和缓存

框架的各种组件（即 Cast 对话框、迷你控制器、展开式控制器和 GCKUIMediaController，如果已配置）将显示当前投放的媒体的海报图片。图片海报图片的网址通常包含在媒体的 GCKMediaMetadata 中，但发件人应用可能有其他网址来源。

GCKUIImagePicker 协议定义了一种方法，用于根据给定的用途和所需大小选择合适的图片。它只有一个方法，即 -[getImageWithHints:fromMetadata:]，该方法会接受 GCKUIImageHints 对象和 GCKMediaMetadata 对象作为参数，并返回 GCKImage 对象作为结果。该框架提供了 GCKUIImagePicker 的默认实现，该实现始终会选择 GCKMediaMetadata 对象中的图片列表中的第一个图片，但应用可以通过设置 GCKCastContext 单例的 imagePicker 属性来提供其他实现。

GCKUIImageCache 协议还定义了一种缓存框架使用 HTTPS 下载的图片的方法。该框架提供了 GCKUIImageCache 的默认实现，该实现会将下载的图片文件存储在应用的缓存目录中，但应用可以通过设置 GCKCastContext 单例的 imageCache 属性来提供其他实现。

后续步骤

至此，您可以向 iOS 发件人应用添加的功能已全部介绍完毕。现在，您可以为其他平台（Android 或 Web）构建发件人应用，也可以构建网站接收器。

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