Keeping screen turned on for certain pages - xamarin.forms

Question

I am using a portable project so do not have direct access to native code.
I have an interface in my project that allows me to access native objects in the Android/iOS projects. We use this primarily for playing audio.
Android, for example, has things like
Window w = new Window();
w.SetFlags(WindowManagerFlags.Fullscreen, WindowManagerFlags.KeepScreenOn);
However the main issue would be accessing a Window object. I could pass a Xamarin.Forms.Page object to the native code, but there would be no way (I don't think) to cast it to a native Android Window object to access the flags.
Is there a way to do this with a portable project?

Answer 1

You can't do this without platform specific services or renderers. A portable project will have to call platform specific code in order to achieve this.
From that platform specific code, either as a DependencyService or Renderer, you can access the Window object through the Forms.Context. The Forms.Context is your Android Activity, through which you can reach the Window object.
On Android it works like this:
Android.Views.Window window = (Forms.Context as Activity).Window;
window.SetFlags(WindowManagerFlags.KeepScreenOn);
On iOS you can try this (Apple docs):
UIApplication.SharedApplication.IdleTimerDisabled = true;

Answer 2

Now there is a plugin doing exactly what Tim wrote
https://learn.microsoft.com/en-us/xamarin/essentials/screen-lock
simple source code is here
https://github.com/xamarin/Essentials/blob/main/Samples/Samples/ViewModel/KeepScreenOnViewModel.cs
using System.Windows.Input;
using Xamarin.Essentials;
using Xamarin.Forms;
namespace Samples.ViewModel
{
public class KeepScreenOnViewModel : BaseViewModel
{
public KeepScreenOnViewModel()
{
RequestActiveCommand = new Command(OnRequestActive);
RequestReleaseCommand = new Command(OnRequestRelease);
}
public bool IsActive => DeviceDisplay.KeepScreenOn;
public ICommand RequestActiveCommand { get; }
public ICommand RequestReleaseCommand { get; }
void OnRequestActive()
{
DeviceDisplay.KeepScreenOn = true;
OnPropertyChanged(nameof(IsActive));
}
void OnRequestRelease()
{
DeviceDisplay.KeepScreenOn = false;
OnPropertyChanged(nameof(IsActive));
}
}
}

Answer 3

For Xamarin Forms Android.
Renders file I included below code
Window window = (Forms.Context as Activity).Window;
window.AddFlags(WindowManagerFlags.KeepScreenOn);