How to remove session in WebView when App is closed?

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How to remove session in WebView when App is closed?

David 356

Hi,

I have found the WebView session cookies are still there when I sign out of a website o or close the mobile app. Is there a way to clear them?

Thanks

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Answer 1

JarvanZhang 23,971

Hello,

Welcome to our Microsoft Q&A platform!

Hi, David. How did you remove the cookies in your project? To remove the cookies in Xamarin.Forms, please achieve the function on each platform. You could call the function code in the shared project using DependencySerive. Here is the related code, you could refer to:

1.Create an interface for the native platform functionality in the shared project.

   namespace TestApplication  
   {  
       public interface IClearCookiesInterface  
       {  
           void ClearAllCookies();  
       }  
   }

2.Implement the interface in the required platform projects and register the platform implementations.

   //android  
   [assembly: Xamarin.Forms.Dependency(typeof(DroidImplementation))]  
   namespace TestApplication.Droid  
   {  
       public class DroidImplementation : IClearCookiesInterface  
       {  
           public void ClearAllCookies()  
           {  
               var cookieManager = CookieManager.Instance;  
               cookieManager.RemoveAllCookie();  
           }  
       }  
   }  
   //ios  
   [assembly: Dependency(typeof(IOSImplementation))]    
   namespace TestApplication.iOS  
   {  
       public class IOSImplementation : IClearCookiesInterface  
       {  
           public void ClearAllCookies()  
           {  
               NSHttpCookieStorage CookieStorage = NSHttpCookieStorage.SharedStorage;  
               foreach (var cookie in CookieStorage.Cookies)  
               {   
                   CookieStorage.DeleteCookie(cookie);  
               }  
           }  
       }  
   }

3.Invoke the function code in the shared project.

   DependencyService.Get<IClearCookiesInterface>().ClearAllCookies();

Best Regards,

Jarvan Zhang

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David 356 Reputation points

2021-04-26T12:14:05.283+00:00

Thank you. I will try this approach.
David 356 Reputation points

2021-04-26T12:46:05.357+00:00
@JarvanZhang Thanks for your help. I have decided to call it directly on iOS and Android when the app is closing.

I tested it on Android like this:

public override void OnCreate() { base.OnCreate(); var cookieManager = Android.Webkit.CookieManager.Instance; cookieManager.RemoveAllCookie(); }

Ideally I would prefer to clear the cookies when the app is closed. Do you know the event for Android and iOS when the app is closed?

Thanks
JarvanZhang 23,971 Reputation points

2021-04-26T13:34:53.247+00:00

Xamarin.Forms project runs on MainActivity class, to detect when the app is closed, try override the OnDestory method of the MainActivity class.

For iOS, you could detect the ApplicationWillTerminate event. But this method may not be called when closing the application. To fix this, try to override the ApplicationDidEnterBackground method and start the BeginBackgroundTaskWithExpirationHandler in it.
David 356 Reputation points

2021-04-26T15:36:03.817+00:00
"To fix this, try to override the ApplicationDidEnterBackground method and start the BeginBackgroundTaskWithExpirationHandler in it."

I guess you mean something like this? Just not sure how I can call the clear cookies

public override void DidEnterBackground(UIApplication application) { nint taskID = UIApplication.SharedApplication.BeginBackgroundTask(() => { }); new System.Threading.Tasks.Task(() => { DoWork(); UIApplication.SharedApplication.EndBackgroundTask(taskID); }).Start(); }

I have also done the independency injection way suggested by @JarvanZhang from Shared project. It's been called from OnStart() and it works on Android. I need to check if this works in iOS.
JarvanZhang 23,971 Reputation points

2021-04-27T14:34:45.25+00:00

Waiting for you update.
David 356 Reputation points

2021-04-29T07:52:11.553+00:00

Hi @JarvanZhang I have not been able to update this until now. I have gone for the DI way and I invoke this DependencyService.Get<IClearCookiesInterface>().ClearAllCookies(); on the shared code onStart().

Will the start event be reliable and be consumed every time the app is open in both platforms? If so, then this is the way I have done.
JarvanZhang 23,971 Reputation points

2021-04-29T08:00:34.143+00:00

Yes, the OnStart method will be called when the application starts. You could call the 'clear' function in it when opening the app next time.

Check the doc: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/app-lifecycle#lifecycle-methods
David 356 Reputation points

2021-04-29T12:18:31.283+00:00

thank you. your solution works.

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How to remove session in WebView when App is closed?

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