Xamarin iOS集成Firebase Crashlytics启动时触发空引用崩溃求助

我正在开发一款Xamarin跨平台iOS和Android应用，已完成Firebase Crashlytics的安装流程，Android端集成后正常工作，但iOS端添加Crashlytics上报代码后，应用启动时崩溃，报错：Object reference not set to an instance of an object.。

调用栈信息如下：

[0:] An error occurred: 'Object reference not set to an instance of an object.'. Callstack: '  at app.iOS.AppDelegate.FinishedLaunching (UIKit.UIApplication app, Foundation.NSDictionary options) [0x00007] in C:\Users\user\source\repos\app\app.iOS\AppDelegate.cs:28 
  at (wrapper managed-to-native) UIKit.UIApplication.xamarin_UIApplicationMain(int,string[],intptr,intptr,intptr&)
  at UIKit.UIApplication.UIApplicationMain (System.Int32 argc, System.String[] argv, System.IntPtr principalClassName, System.IntPtr delegateClassName) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/16.2.0.5/src/Xamarin.iOS/UIKit/UIApplication.cs:57 
  at UIKit.UIApplication.Main (System.String[] args, System.Type principalClass, System.Type delegateClass) [0x0003b] in /Library/Frameworks/Xamarin.iOS.framework/Versions/16.2.0.5/src/Xamarin.iOS/UIKit/UIApplication.cs:92 
  at diarioDeTeruelIOS.iOS.Application.Main (System.String[] args) [0x00001] in C:\Users\user\source\repos\app\app.iOS\Main.cs:14 
  at (wrapper managed-to-native) System.Reflection.RuntimeMethodInfo.InternalInvoke(System.Reflection.RuntimeMethodInfo,object,object[],System.Exception&)
  at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x0006a] in /Library/Frameworks/Xamarin.iOS.framework/Versions/Current/src/Xamarin.iOS/mcs/class/corlib/System.Reflection/RuntimeMethodInfo.cs:395 '
The app has been terminated.

目前确认Firebase.iOS.Core相关功能无异常，仅调用Firebase.iOS.Crashlytics类/方法时出现问题。开发环境为Visual Studio 2022，基于.NET Standard 2.1，调试设备为实体iPhone 7。

AppDelegate.cs代码如下：

namespace app.iOS
{
    // The UIApplicationDelegate for the application. This class is responsible for launching the 
    // User Interface of the application, as well as listening (and optionally responding) to 
    // application events from iOS.
    [Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {
        //
        // This method is invoked when the application has loaded and is ready to run. In this 
        // method you should instantiate the window, load the UI into it and then make the window
        // visible.
        //
        // You have 17 seconds to return from this method, or iOS will terminate your application.
        //
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            Initializer.Initialize();
            global::Xamarin.Forms.Forms.Init();
            LoadApplication(new App());
            Firebase.Core.App.Configure();

                Crashlytics.SharedInstance.Init();
                Crashlytics.SharedInstance.SetCrashlyticsCollectionEnabled(true);
                Crashlytics.SharedInstance.SendUnsentReports();
            /*
             * 
             */


            return base.FinishedLaunching(app, options);
        }
    }
}

可能的解决方案 #

• 确认Firebase.iOS.Crashlytics NuGet包版本与Firebase.iOS.Core完全兼容，避免版本不匹配导致的实例化失败
• 检查GoogleService-Info.plist是否已正确添加到iOS项目，且Build Action设置为BundleResource
• 调整初始化顺序，将Firebase Core配置移至Xamarin Forms初始化之前：

  public override bool FinishedLaunching(UIApplication app, NSDictionary options)
  {
      Firebase.Core.App.Configure();
      Initializer.Initialize();
      global::Xamarin.Forms.Forms.Init();
      LoadApplication(new App());
  
      Crashlytics.SharedInstance.Init();
      Crashlytics.SharedInstance.SetCrashlyticsCollectionEnabled(true);
      Crashlytics.SharedInstance.SendUnsentReports();
  
      return base.FinishedLaunching(app, options);
  }
  

• 清理iOS项目的bin/obj目录，重新生成整个解决方案
• 卸载设备上的现有应用，重新部署调试
• 检查Info.plist中是否配置了Crashlytics所需的网络权限（iOS默认允许HTTP/HTTPS请求，但可确认是否存在限制）

内容的提问来源于stack exchange，提问作者Lorem