Google Chromecast SDK TearDown 在后台

Question

使用 iOS Sender API 框架，当我的应用程序进入后台时，SDK 会断开所有连接，并且在应用程序重新回到前台之前，我无法启动任何媒体。我的应用程序播放音频并允许在后台运行和流式传输。是否可以选择告诉 Googlecast 框架保持套接字打开？

这是后台日志：

INFO：将主动辞职

信息：现在在后台

FINE: -[GCKCastSocket disconnect] 断开连接

FINE: -[GCKCastSocket doTeardownWithError:] doTeardownWithError

FINE: -[GCKCastSocket doTeardownWithError:] 通知委托套接字已断开

FINE: -[GCKHeartbeatChannel didDisconnect] 已断开连接 - 必要时停止心跳计时器

FINE: -[GCKCastSocket socketDidDisconnect:withError:] socketDidDisconnect:withError: "(null)"

然后当应用程序恢复时： 信息：进入前台

FINE: -[GCKCastSocket doTeardownWithError:] doTeardownWithError

FINE: -[GCKCastSocket doTeardownWithError:] 通知委托套接字已断开

FINE: -[GCKCastSocket connectToHost:port:withTimeout:] 正在连接到端口 8009l 上的“192.168.1.4”...

INFO：已激活

FINE: -[GCKCastSocket socket:didConnectToHost:port:] socketDidConnect:

FINE: -[GCKCastSocket socketDidSecure:] socketDidSecure:

FINE: -[GCKCastSocket socket:didReadData:withTag:] 前缀读取，预期消息长度=1307

FINE: -[GCKDeviceAuthChannel didReceiveBinaryMessage:] 正版 Google 设备 didDeviceAuthenticated=YES

FINE: -[GCKDeviceManager deviceAuthChannelDidAuthenticate:] Authentic device，连接接收通道

FINE: -[GCKCastSocket socket:didReadData:withTag:] 前缀读取，预期消息长度=474

FINE: -[GCKDeviceManager receiverControlChannel:didReceiveStatusForApplication:] 加入申请（CC1AD845）可用

FINE: -[GCKDeviceManager connectAndNotifyDidConnectToApplication:launchedApplication:] 连接到应用程序 默认媒体接收器 (CC1AD845)，传输 ID web-11

FINE: -[GCKCastSocket socket:didReadData:withTag:] 前缀读取，预期消息长度=135

FINE: -[GCKMediaControlChannel didReceiveTextMessage:] 收到消息：{"type":"MEDIA_STATUS","status":[],"requestId":6}

Answer 1

在 iOS Sender API 2.0 版中，GCKCastSocket 在收到 UIApplicationDidEnterBackgroundNotification 时关闭，这不是可以配置的。

这意味着：

• 当应用在后台时，不能将新媒体从应用推送到 chromecast
• 无法实现锁屏控制

替代方案（仅限自定义接收器）：

• 将要播放的媒体列表发送给接收器
• 直接从接收器从云端获取新媒体

有关详细信息，另请参阅 this question 或 this one。

Answer 2

这是我用于其他需求的解决方案，但我想它也可以在这里应用（尚未测试）

1.创建一个后台任务处理程序作为 dispatch_block_t，比如说

 dispatch_block_t myDummyBackgroundTaskBlock = {
    [[UIApplication sharedApplication] endBackgroundTask:myDummyBackgroundTask];
    myDummyBackgroundTask = UIBackgroundTaskInvalid;
    myDummyBackgroundTask = [app beginBackgroundTaskWithExpirationHandler:myDummyBackgroundTask];
};

2。在某处定义此后台和前台任务处理程序

    // foreground
    -(void)handleTasksForApplicationInForeground {
    if(myDummyBackgroundTask) { // reset that task
       [[UIApplication sharedApplication] endBackgroundTask: myDummyBackgroundTask];
       myDummyBackgroundTask = UIBackgroundTaskInvalid;
     }
    }

     // background
     -(void) handleTasksForApplicationInBackground {
         UIDevice *device = [UIDevice currentDevice];
         BOOL backgroundSupported = NO;
        if ([device respondsToSelector:@selector(isMultitaskingSupported)])
         backgroundSupported = device.multitaskingSupported;
        if(backgroundSupported && backgroundEnabled) { // perform a background task

            myDummyBackgroundTaskBlock = ^{
                [[UIApplication sharedApplication] endBackgroundTask: myDummyBackgroundTaskBlock];
                myDummyBackgroundTaskBlock = UIBackgroundTaskInvalid;
           };

           SEL sel = @selector(doDummyBackgroundTask);
           [self doBackgroundTaskAsync:sel];

           [self performSelector:@selector(doBackgroundTaskAsync:) withObject:nil afterDelay:500.0f]; /// LP: this is the funny part since iOS will kill the task after 500 sec.
             }
           }

3。现在让我们在应用程序中处理委托后台模式（如之前定义的那样，您可以在应用程序 .plist 中使用不同的选项激活后台模式）：

    -(void)applicationDidEnterBackground:(UIApplication *)application {
       [self handleTasksForApplicationInBackground];
     }

    -(void)applicationWillEnterForeground:(UIApplication *)application {
       [self handleTasksForApplicationInForeground];
     }

4。让我们看看后台异步任务选择器做了什么

        -(void) doBackgroundTaskAsync:(SEL)selector {

        @try {
             if( [[UIApplication sharedApplication] backgroundTimeRemaining] < 5 ) { 
               return;
             }

           if(!myDummyBackgroundTaskBlock) { // need to create again on-the-fly
                myDummyBackgroundTaskBlock = ^{
                      [[UIApplication sharedApplication] endBackgroundTask:myDummyBackgroundTask];
                     myDummyBackgroundTask = UIBackgroundTaskInvalid;
                };
             }

            myDummyBackgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:myDummyBackgroundTaskBlock];
          dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

           while ([[UIApplication sharedApplication] backgroundTimeRemaining] > 5.0) {
              int delta = 5.0;
              [self performSelector: selector ];
              sleep(delta);
          }
        });
      }
       @catch (...) {
     }
    }