如何正确使用“openParentApplication”和“handleWatchKitExtensionRequest”以便调用“reply()”？

Question

情况：我在Watch应用中使用openParentApplication在主应用中调用handleWatchKitExtensionRequest。这在模拟器中运行良好，并且在 iPhone 应用程序处于活动/打开状态时也适用于实际设备（Apple Watch 和 iPhone）。

问题：当我在实际设备（Apple Watch 和 iPhone）上运行它时，handleWatchKitExtensionRequest 不会在主 iPhone 应用程序未激活/未打开时将数据返回到 openParentApplication。

WatchKit 扩展中 InterfaceController.m 中的代码：

NSDictionary *requst = @{ @"request" : @"getData" };
[InterfaceController openParentApplication:requst
                                     reply:^( NSDictionary *replyInfo, NSError *error ) {
                                        // do something with the returned info
                                     }];

iPhone 上主应用的应用委托中的代码：

- (void)application:(UIApplication *)application handleWatchKitExtensionRequest:(NSDictionary *)userInfo reply:(void ( ^)( NSDictionary * ))reply
{
  if ( [[userInfo objectForKey:@"request"] isEqualToString:@"getData"] )
  {
    // get data
    // ...
    reply( data );
  }
}

Answer 1

当 iPhone 上的主应用程序未激活时，可能无法到达reply()，因为后台任务之前被操作系统杀死。

解决方案是在handleWatchKitExtensionRequest 中显式启动后台任务，如documentation 中指定的那样。如果像这样启动后台任务，它最多可以运行 180 秒。这可确保 iPhone 上的主应用在发送回复之前不会暂停。

iPhone 上主应用的应用委托中的代码：

- (void)application:(UIApplication *)application handleWatchKitExtensionRequest:(NSDictionary *)userInfo reply:(void ( ^)( NSDictionary * ))reply
{
   __block UIBackgroundTaskIdentifier watchKitHandler;
   watchKitHandler = [[UIApplication sharedApplication] beginBackgroundTaskWithName:@"backgroundTask"
                                                               expirationHandler:^{
                                                                 watchKitHandler = UIBackgroundTaskInvalid;
                                                               }];

   if ( [[userInfo objectForKey:@"request"] isEqualToString:@"getData"] )
   {
      // get data
      // ...
      reply( data );
   }

   dispatch_after( dispatch_time( DISPATCH_TIME_NOW, (int64_t)NSEC_PER_SEC * 1 ), dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0 ), ^{
      [[UIApplication sharedApplication] endBackgroundTask:watchKitHandler];
   } );
}

如果需要异步获取数据，请使用如下方式确保方法不会立即返回（不调用reply）：

- (void)application:(UIApplication *)application handleWatchKitExtensionRequest:(NSDictionary *)userInfo reply:(void ( ^)( NSDictionary * ))reply
{ 
    __block UIBackgroundTaskIdentifier watchKitHandler;

    watchKitHandler = [[UIApplication sharedApplication] beginBackgroundTaskWithName:@"backgroundTask"
                                                               expirationHandler:^{
                                                                   watchKitHandler = UIBackgroundTaskInvalid;
                                                               }];  

   NSMutableDictionary *response = [NSMutableDictionary dictionary];

   dispatch_semaphore_t sema = dispatch_semaphore_create(0);

   [ClassObject getDataWithBlock:^(BOOL succeeded, NSError *error){

        if (succeeded)
        {
            [response setObject:@"update succeded" forKey:@"updateKey"];
        }
        else
        {
            if (error)
            {
                [response setObject:[NSString stringWithFormat:@"update failed: %@", error.description] forKey:@"updateKey"]; 
            }
            else
            {
                [response setObject:@"update failed with no error" forKey:@"updateKey"];
            }
        }

        reply(response);
        dispatch_semaphore_signal(sema);
    }];

    dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);

    dispatch_after(dispatch_time( DISPATCH_TIME_NOW, (int64_t)NSEC_PER_SEC * 1), dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    [[UIApplication sharedApplication] endBackgroundTask:watchKitHandler];
  });
}