Xamarin.Forms Dependency Service non-static fields/properties

Question

I'm using Dependency Service to get the platform specific implementation of an interface. Let's say I have the following interface:

public interface IMyInterface
{
    bool IsEnabled { get; set; }
}

And the implementing class in my Android project:

[assembly: Dependency(typeof(MyClass))]
namespace App.Droid
{
    class MyClass : IMyInterface
    {
        public bool IsEnabled { get; set; }
    }
} 

At some point in the code, I set IsEnabled to true .

After that, I start a new activity that makes my app go to background:

Intent intent = new Intent();
intent.SetAction(action);
intent.SetFlags(ActivityFlags.NewTask);

MainActivity.Instance.StartActivity(intent);

When my app returns to foreground, I access the property IsEnabled and I get false instead of true . This actually happens with every single property and private field of the impementing class. Are those properties garbage collected when I leave the app for a new activity?

The only way I found to solve this issue is to make all backing fields static , but this makes a lot of overhead in the code, which might be unnecessary if I knew the reasons under this behavoiur.

Answer 1

Not too understanding the title of your question.

If you use the singleton pattern, you can extract the properties based on the unique instantiation object when needed.Like this:

public class Singleton
    {
        // Define a static variable to hold an instance of the class
        private static Singleton uniqueInstance;

        // Define a private constructor so that the outside world cannot create instances of the class
        private Singleton()
        {
        }

        /// <summary>
        /// Define public methods to provide a global access point, and you can also define public properties to provide global access points
        /// </summary>
        /// <returns></returns>
        public static Singleton GetInstance()
        {
            // Create if the instance of the class does not exist, otherwise return directly
            if (uniqueInstance == null)
            {
                uniqueInstance = new Singleton();
            }
            return uniqueInstance;
        }
    }

If not , you can use Properties ( https://docs.microsoft.com/en-us/dotnet/api/xamarin.forms.application.properties?view=xamarin-forms)to access the data .Like this:

private void SaveConnectionData(JSON.Connection C)
                    {
                        App.Current.Properties[Cryptography.Encryption("AccessToken")] = Cryptography.Encryption(C.Access_token);
                        App.Current.Properties[Cryptography.Encryption("ExpiresIn")] = Cryptography.Encryption(C.Expires_in.ToString());
                        App.Current.Properties[Cryptography.Encryption("TokenType")] = Cryptography.Encryption(C.Token_type);
                        App.Current.Properties[Cryptography.Encryption("Scope")] = Cryptography.Encryption(JsonConvert.SerializeObject(C.Scope));
                        App.Current.Properties[Cryptography.Encryption("RefreshToken")] = Cryptography.Encryption(C.Refresh_token);
                        App.Current.SavePropertiesAsync();
                    }

You may be involved in the use of lifecycles and notifications .Also if there is a lot of data, consider using the SQLite database to save this data .Can refer to this link here

More :In Xamarin.Android, you also can try lifecycles to show saved data.Like OnResume method to show data.