Dynamically setting light/dark themes at runtime about fabulous.xamarinforms HOT 2 OPEN

For anyone coming across this in the future, I managed to get most of what I was hoping for by overriding OnResume(). For example:

type App () as app = 
    inherit Application ()

    let runner = 
        App.program
        |> XamarinFormsProgram.run app

    override this.OnResume () =
        runner.Dispatch App.Msg.RefreshTheme

from fabulous.xamarinforms.

@gaelian . I'm implementing a similar use case and what I end up doing was to :

• Listen for the global theme changed event
  let runner =
  Program.mkProgram App.init App.update App.view
  |> XamarinFormsProgram.run app

  let onRequestedThemeChanged =
  EventHandler(fun _ args -> runner.Dispatch(Msg.AppThemeChanged args.RequestedTheme))

  override this.OnStart() =
  Application.Current.RequestedThemeChanged.AddHandler(onRequestedThemeChanged)`

• The on the AppThemeChanged make and batch update to all the views to switch the styles to the respective theme
  | AppThemeChanged appTheme ->
  let loginAppThemeMsg =
  LoginPage.Msg.SetRequestedAppTheme appTheme

  let loanAppThemeMsg =
    LoanCommon.Msg.SetRequestedAppTheme appTheme
  
  let cmd =
    Cmd.batch [ Cmd.ofMsg (LoginPageMsg loginAppThemeMsg)
                Cmd.ofMsg (NewLoanStepsMsg loanAppThemeMsg) ]
  
  model, cmd
  

• You can find a sample on the AllControls sample https://github.com/fsprojects/Fabulous/blob/8bbb610a2bbfe239e175b8e25ac950d55ebc94f5/Fabulous.XamarinForms/samples/AllControls/AllControls/Samples/UseCases/AppTheming.fs#L7

• To make sure the view are force be updated you need to add a property to all the model affected and use that in the view so the view will be forced to updated

from fabulous.xamarinforms.