Persistent Storage using Application.Current.Properties not working

Question

I'm trying to achieve a persistent storage in Xamarin.Forms. After researching in Xamarin.Forms, I decided to use Application.Current.Properties property.

It looks like it is working just only if the app still remains alive. If I close the app and start it again the Application.Current.Properties is empty.

Does anyone know if I'm doing something wrong? Can I achieve this feature in another way?

As usual, thanks guys.

Solution 1

I have had a ton of problems with Application.Current.Properties on Android. I highly suggest using Xamarin Settings plugin instead which I have never had any issues with. It is persistent even when the app is closed.

That being said Application.Current.Properties is supposed to work even when you close the app. Not sure why it wouldn't but it does not surprise me either.

*Edit: To use once it is installed, basically CrossSettings.Current is the plugin class that will do the work but the example just creates a separate property to access it. So create a new file, lets call it SettingsImplementation:

public static class SettingsImplementation {

    #region Instance

    private static Lazy<ISettings> _appSettings;

    public static ISettings AppSettings {
        get {
            if(_appSettings == null) {
                _appSettings = new Lazy<ISettings>(() => CrossSettings.Current, LazyThreadSafetyMode.PublicationOnly);
            }

            return _appSettings.Value;
        }
        set {
            _appSettings = new Lazy<ISettings>(() => value, LazyThreadSafetyMode.PublicationOnly);
        }
    }

    #endregion

    private const string UserNameKey = "username_key"; //Key used to get your property
    private static readonly string UserNameDefault = string.Empty; //Default value for your property if the key-value pair has not been created yet

    public static string UserName {
        get { return AppSettings.GetValueOrDefault<string>(UserNameKey, UserNameDefault); }
        set { AppSettings.AddOrUpdateValue<string>(UserNameKey, value); }
    }
}

Then to use that you would do this anywhere in your app:

SettingsImplementation.UserName = "something";

OR

string username = SettingsImplementation.UserName;

Solution 2

you can use Xamarin essentials "Preferences" instead:

Preferences.Set("Key", "Value");
Preferences.Get("Key", "Default");

Solution 3

I ran into the same issue.

The problem:

I was trying to throw complex objects into the Application Properties.

It turns out that the Properties can only take primitive data typs.

This Blog was very helpfull.

https://codemilltech.com/persist-whatever-you-want-with-xamarin-forms/

Comments

[Elias MP]

Hi @hvaughan3, first at all thanks for the answer. It looks like will work for me. An stupid question, I can´t use the plugin following the manual... Can you give me a hand?

[Elias MP]

I installed the package, and then I added it to each solution, but I dont know what I´m doing wrong. I can´t use AppSettings.GetValueOrDefault...

[Elias MP]

public static class Settings is created in my rootnamespace.ViewModel.Helpers but Visual don´t recognize the class...

[hvaughan3]

@EliasMP Sorry, just seeing this. Let me edit my answer.

[Elias MP]

Thanks mate for helping me. :)

[hvaughan3]

@EliasMP Np. Please see edit. I think those Plugin.Settings namespaces are correct but I could have them backwards. Let me know if you still get errors

[Elias MP]

It works! Even when I turn on again the app. Thanks @hvaughan3. Glad to meet you today. :)))))

[iBobb]

It is recommended, to include some information from links providing solutions. The main point here is: to go around the fact that you can only save primitive types such as strings in Application.Current.Properties you can serialize your object into a JSON string and save it like that :)

[ho h]

What should be written inside "something"? And SettingsImplementation.UserName where to use?

[hvaughan3]

something is any unique key that you want to use to save your value. Each value you want to save will need its own unique key. You would use SettingsImplementation.UserName where ever you need to use that saved value. If you are saving a user's username, then maybe you use it to prefill the login username field or you display in on their profile page. When they want to change their username you assign the new value to it SettingsImplementation.UserName = "MyNewUserName"