Keep immersive mode all over the app on Android, Xamarin.forms

Question

I want to keep immersive mode all over the app on Android using Xamarin.forms. I have read few blogs and posts. This one works but only until I press an input text box or I scroll over the screen. I want to avoid this. This question debate my concern but I don't understand the solution. Maybe it is obsolete. My android device is 7.1 and this is my code on my .Android MainActivity, void OnCreate, void OnCreate:

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity{
    protected override void OnCreate(Bundle savedInstanceState){
        Xamarin.Essentials.Platform.Init(this, savedInstanceState);
        global::Xamarin.Forms.Forms.Init(this, savedInstanceState);

        TabLayoutResource = Resource.Layout.Tabbar;
        ToolbarResource = Resource.Layout.Toolbar;
        base.OnCreate(savedInstanceState);
        LoadApplication(new App());

        ImmersiveMode();
    }

    public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults){
        Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

        base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    public void ImmersiveMode() {
        int uiOptions = (int)(Forms.Context as Activity).Window.DecorView.SystemUiVisibility;
        uiOptions |= (int)SystemUiFlags.Fullscreen;
        uiOptions |= (int)SystemUiFlags.HideNavigation;
        uiOptions |= (int)SystemUiFlags.ImmersiveSticky;
        (Forms.Context as Activity).Window.DecorView.SystemUiVisibility = (StatusBarVisibility)uiOptions;
    }
}

How could I resolve this? Could you be specific on where I should located the new code. I'm noob on Xamarin.Forms and it looks tricky for me. Thank you

Edit: this code:

this.Window.AddFlags(WindowManagerFlags.Fullscreen); on the .Android MainActivity hides the Android bar with the wifi signal, time, bluetooth, etc.

Is there a line like that one to hide this android buttons?

Answer 1

Window.DecorView.SystemUiVisibility is deprecated as of Android R (11). There is a new way to do this in this API version.

Below is the code I used in one of my apps. I had to override a bunch of methods in MainActivity class.

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.OS;
using Android.Views;

namespace SampleApp.Droid
{
    [Activity(Label = "SampleApp", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize )]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            LoadApplication(new App());
            SetFullscreenFlags();
        }

        protected override void OnResume()
        {
            base.OnResume();
            SetFullscreenFlags();
        }

        public override void OnWindowFocusChanged(bool hasFocus)
        {
            base.OnWindowFocusChanged(hasFocus);
            SetFullscreenFlags();
        }

        protected void SetFullscreenFlags()
        {
            var attrs = Window.Attributes;
            attrs.Flags |= WindowManagerFlags.Fullscreen;
            Window.Attributes = attrs;

            // BuildVersionCodes has a wrong value for Android R (1000 instead of 30)
            // https://github.com/xamarin/xamarin-android/issues/5723
            // if (Build.VERSION.SdkInt >= BuildVersionCodes.R)
            if ((int)Build.VERSION.SdkInt >= 30)
            {
                Window.SetDecorFitsSystemWindows(false);

                if (Window.InsetsController != null)
                {
                    Window.InsetsController.Hide(WindowInsets.Type.NavigationBars());
                    Window.InsetsController.Hide(WindowInsets.Type.StatusBars());
                    Window.InsetsController.Hide(WindowInsets.Type.SystemBars());
                    Window.InsetsController.Show(WindowInsets.Type.Ime());
                }
            }
            else
            {
                var uiOptions = (int)Window.DecorView.SystemUiVisibility;
                var newUiOptions = (int)uiOptions;

                newUiOptions |=
                    (int)SystemUiFlags.LayoutStable |
                    (int)SystemUiFlags.LayoutHideNavigation |
                    (int)SystemUiFlags.LayoutFullscreen |
                    (int)SystemUiFlags.HideNavigation |
                    (int)SystemUiFlags.Fullscreen |
                    (int)SystemUiFlags.ImmersiveSticky;

                Window.DecorView.SystemUiVisibility = (StatusBarVisibility)newUiOptions;
            }
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }

    }
}

Previously, I also implemented the View.IOnSystemUiVisibilityChangeListener interface. But it is also deprecated and will be removed in future versions:

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity, View.IOnSystemUiVisibilityChangeListener
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        // omitted code

        Window.DecorView.SetOnSystemUiVisibilityChangeListener(this);
    }

    public void OnSystemUiVisibilityChange([GeneratedEnum] StatusBarVisibility visibility)
    {
        SetFullscreenFlags();
    }
}

EDIT:

If you want to keep immersive mode after user focus some input control on your screen you can implement ViewTreeObserver.IOnGlobalFocusChangeListener interface. Here's how I did:

public class MainActivity : 
    global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity, 
    ViewTreeObserver.IOnGlobalFocusChangeListener
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        // ommited code
    }

    public override void SetContentView(View view)
    {
        base.SetContentView(view);

        if (view?.ViewTreeObserver != null)
            view.ViewTreeObserver.AddOnGlobalFocusChangeListener(this);
    }

    public override void SetContentView(View view, ViewGroup.LayoutParams @params)
    {
        base.SetContentView(view, @params);

        if (view?.ViewTreeObserver != null)
            view.ViewTreeObserver.AddOnGlobalFocusChangeListener(this);
    }

    public void OnGlobalFocusChanged(View oldFocus, View newFocus)
    {
        SetFullscreenFlags();
    }
}