App crashes after throwing an error ' Window was already created'

Question

Platform : Android

Version : MAUI 8

Description :

I was trying to invoke platform specific code by implementing broadcast Receiver for android, When I tried to register the receiver onResume( ) , app crashed with an error "Window was already created" . The same code works fine in Xamarin though.

  protected override void OnResume()
  {
      base.OnResume();
      if (null != _broadcastReceiver)
      {
          // Register the broadcast receiver
          IntentFilter filter = new IntentFilter(DataWedgeReceiver.IntentAction);
          filter.AddCategory(DataWedgeReceiver.IntentCategory);
          Android.App.Application.Context.RegisterReceiver(_broadcastReceiver, filter);
      }
  }

Answer 1

Hello,

You can move MainActivity.cs code to the App.xaml.cs.

Base on this Cross-platform lifecycle events.

Window.Create corresponds to the Android platform's OnPostCreate Window.Activated corresponds to the Android platform's OnResume Window.Deactivated corresponds to the Android platform's OnPause

Here is my edited code in the App.xaml.cs.

#if ANDROID
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.OS;
 
using CommunityToolkit.Mvvm.Messaging;
using CommunityToolkit.Mvvm.Messaging.Messages;
using MauiApp5.Platforms.Android;
#endif
 
namespace MauiApp5
{
    public partial class App : Microsoft.Maui.Controls.Application
    {
        public App()
        {
            InitializeComponent();
 
          MainPage =new AppShell();
        }
        protected override Window CreateWindow(IActivationState? activationState)
        {
 
            Window window = base.CreateWindow(activationState);
#if ANDROID
            window.Created += (s, e) =>
            {
                // Custom logic
 
                RegisterReceivers();
                _broadcastReceiver = new DataWedgeReceiver();
                LaserScanModel helpermodel = LaserScanModel.GetInstance();
 
 
                _broadcastReceiver.scanDataReceived += (s, scanData) =>
                {
                    WeakReferenceMessenger.Default.Send(new ItemMessage(scanData), "LaserScan");
                };
                CreateProfile();
 
            };
            window.Activated += (s, e) =>
            {
                if (null != _broadcastReceiver)
                {
                    // Register the broadcast receiver
                    IntentFilter filter = new IntentFilter(DataWedgeReceiver.IntentAction);
                    filter.AddCategory(DataWedgeReceiver.IntentCategory);
                   Platform.AppContext.RegisterReceiver(_broadcastReceiver, filter);
                }
 
            };
 
            window.Deactivated += (s, e) =>
            {
 
                if (null != _broadcastReceiver)
                {
                    // Unregister the broadcast receiver
                    Platform.AppContext.UnregisterReceiver(_broadcastReceiver);
                }
 
            };
 
#endif
            return window;
        }
 
#if ANDROID
 
        private static string ACTION_DATAWEDGE_FROM_6_2 = "com.symbol.datawedge.api.ACTION";
        private static string EXTRA_CREATE_PROFILE = "com.symbol.datawedge.api.CREATE_PROFILE";
        private static string EXTRA_SET_CONFIG = "com.symbol.datawedge.api.SET_CONFIG";
        private static string EXTRA_PROFILE_NAME = "Inventory DEMO";
        public static DataWedgeReceiver _broadcastReceiver = null;
 
        void RegisterReceivers()
        {
            IntentFilter filter = new IntentFilter();
            filter.AddCategory("android.intent.category.DEFAULT");
            filter.AddAction("com.ndzl.DW");
 
            Intent regres = Platform.CurrentActivity.RegisterReceiver(new DataWedgeReceiver(), filter);
        }
 
 
        void CreateProfile()
        {
            string profileName = EXTRA_PROFILE_NAME;
            SendDataWedgeIntentWithExtra(ACTION_DATAWEDGE_FROM_6_2, EXTRA_CREATE_PROFILE, profileName);
 
            //  Now configure that created profile to apply to our application
            Bundle profileConfig = new Bundle();
            profileConfig.PutString("PROFILE_NAME", profileName);
            profileConfig.PutString("PROFILE_ENABLED", "true"); //  Seems these are all strings
            profileConfig.PutString("CONFIG_MODE", "UPDATE");
            Bundle appConfig = new Bundle();
            appConfig.PutString("PACKAGE_NAME", Android.App.Application.Context.PackageName);      //  Associate the profile with this app
            appConfig.PutStringArray("ACTIVITY_LIST", new string[] { "*" });
            profileConfig.PutParcelableArray("APP_LIST", new Bundle[] { appConfig });
 
            //BARCODE READER
            Bundle barcodeProps = new Bundle();
            barcodeProps.PutString("barcode_trigger_mode", "1");
            Bundle barcodeConfig = new Bundle();
            barcodeConfig.PutString("PLUGIN_NAME", "BARCODE");
            barcodeConfig.PutString("RESET_CONFIG", "true"); //  This is the default but never hurts to specify
            barcodeConfig.PutBundle("PARAM_LIST", barcodeProps);
 
            //INTENT
            Bundle intentProps = new Bundle();
            intentProps.PutString("intent_output_enabled", "true");
            intentProps.PutString("intent_action", DataWedgeReceiver.IntentAction);
            intentProps.PutString("intent_delivery", "2");
            Bundle intentConfig = new Bundle();
            intentConfig.PutString("PLUGIN_NAME", "INTENT");
            intentConfig.PutString("RESET_CONFIG", "true");
            intentConfig.PutBundle("PARAM_LIST", intentProps);
 
            // Add configurations into a collection
            profileConfig.PutParcelableArray("PLUGIN_CONFIG", new Bundle[] { barcodeConfig, intentConfig });
            SendDataWedgeIntentWithExtra(ACTION_DATAWEDGE_FROM_6_2, EXTRA_SET_CONFIG, profileConfig);
        }
        void SendDataWedgeIntentWithExtra(String action, String extraKey, Bundle extras)
        {
            Intent dwIntent = new Intent();
            dwIntent.SetAction(action);
            dwIntent.PutExtra(extraKey, extras);
            Platform.AppContext.SendBroadcast(dwIntent);
        }
        void SendDataWedgeIntentWithExtra(String action, String extraKey, String extraValue)
        {
            Intent dwIntent = new Intent();
            dwIntent.SetAction(action);
            dwIntent.PutExtra(extraKey, extraValue);
            Platform.AppContext.SendBroadcast(dwIntent);
        }
 
#endif
    }
}

As note: please keep the MainActivity.cs to the empty like following code.

[Activity(Theme = "@style/Maui.SplashTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
public class MainActivity : MauiAppCompatActivity
{

 
    
}

Best Regards,

Leon Lu

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