Xamarin iOS后台任务永久运行方案咨询（规避定位API高耗电问题）

Hey there, let's tackle your iOS background persistence issue with Xamarin—this is a common pain point given Apple's strict background execution rules, but we've got some actionable paths to explore.

First, to address your core question: Xamarin.iOS does not currently offer official, out-of-the-box support for Local Push Connectivity (introduced in WWDC 2020). While the underlying iOS SDK includes this functionality, Xamarin's binding layer hasn't wrapped these APIs for direct C# use yet, and you won't find official documentation for it in Xamarin's docs.

If you're dead-set on using Local Push Connectivity, you could build a custom native binding: write the necessary Objective-C/Swift code to implement the feature, then create a Xamarin binding project to expose those APIs to your C# code. That said, this requires solid native iOS development skills and adds maintenance overhead, especially as Apple updates the SDK.

Since you can't use location APIs, have no internet access, and need low power usage, here are Apple-approved alternatives that work with Xamarin:

1. Background Tasks Framework (iOS 13+) #

This is the most reliable, low-power option for periodic background work without violating Apple's rules. Unlike Background Fetch, the Background Tasks Framework lets you schedule longer-running tasks and have more control over execution timing.

Setup Steps in Xamarin: #

• Add the BGTaskSchedulerPermittedIdentifiers key to your Info.plist, listing your task identifiers (e.g., com.your.app.periodicupdate).
• Register your task handler in AppDelegate.FinishedLaunching:

  BGTaskScheduler.Shared.Register("com.your.app.periodicupdate", null, HandlePeriodicTask);
  

• Implement the task handler:

  void HandlePeriodicTask(BGTask task)
  {
      // Execute your background logic here (keep it efficient!)
      // Mark the task as complete when done
      task.SetTaskCompleted(true);
  
      // Reschedule the task for next time
      var nextRequest = new BGAppRefreshTaskRequest("com.your.app.periodicupdate");
      nextRequest.EarliestBeginDate = DateTime.Now.AddMinutes(15); // Adjust timing as needed
      try
      {
          BGTaskScheduler.Shared.SubmitAsync(nextRequest).Wait();
      }
      catch (Exception ex)
      {
          Console.WriteLine($"Failed to reschedule task: {ex.Message}");
      }
  }
  

• Submit the initial task request when your app enters the background:

  public override void DidEnterBackground(UIApplication application)
  {
      var request = new BGAppRefreshTaskRequest("com.your.app.periodicupdate");
      request.EarliestBeginDate = DateTime.Now.AddMinutes(5);
      try
      {
          BGTaskScheduler.Shared.SubmitAsync(request).Wait();
      }
      catch (Exception ex)
      {
          Console.WriteLine($"Failed to submit task: {ex.Message}");
      }
  }
  

Apple controls execution frequency to save power, but this is far more consistent than Background Fetch and uses minimal battery.

2. Bluetooth Low Energy (BLE) Background Mode #

If your app interacts with local BLE devices (e.g., sensors, peripherals), enabling BLE background mode lets iOS keep your app active to monitor BLE events—this is extremely low-power and fully Apple-approved.

Setup in Xamarin: #

• Add the bluetooth-central (if your app is a central device) or bluetooth-peripheral (if it's a peripheral) value to the UIBackgroundModes array in Info.plist.
• Use Xamarin's CoreBluetooth bindings to manage BLE connections and listen for events like peripheral disconnects or data updates. iOS will wake your app in the background when these events occur, even if the app was suspended.

3. Voice over IP (VoIP) Background Mode (Use with Caution) #

If your app has a legitimate VoIP use case (e.g., local voice communication without internet), enabling the VoIP background mode lets iOS keep your app active to listen for incoming calls. However, Apple strictly enforces this mode—if your app doesn't provide actual VoIP functionality, it will get rejected from the App Store.

Setup in Xamarin: #

• Add voip to the UIBackgroundModes array in Info.plist.
• Use Xamarin's PushKit bindings to manage VoIP push notifications (though since you have no internet, you'd need to handle local connection monitoring instead).

4. Background Audio (Last Resort) #

As a last-ditch option, you can play a silent audio track in the background to keep your app active. This is a bit of a workaround, so Apple may reject it if your app has no legitimate audio purpose. That said, it's low-power compared to location APIs.

Setup in Xamarin: #

• Add audio to the UIBackgroundModes array in Info.plist.
• Use AVFoundation to play a looped silent audio file (ensure the audio is formatted correctly to avoid being flagged as invalid).

Always align your background implementation with Apple's background execution guidelines—any workaround that violates these rules will lead to App Store rejection or unexpected termination by iOS.

内容的提问来源于stack exchange，提问作者bigboss