In Xamarin Forms how to call MainActivity's method or get MainActivity's 'Window' from another class? - xamarin

Question

I want to hide software buttons when enter text to entry is done. When user put finger outside keyboard, this method is invoked:
public override void OnUserInteraction()
{
base.OnUserInteraction();
HideSoftwareMenuBars();
}
That works perfectly:
private void HideSoftwareMenuBars()
{
try
{
int uiOptions = (int)Window.DecorView.SystemUiVisibility;
uiOptions |= (int)SystemUiFlags.LayoutStable;
uiOptions |= (int)SystemUiFlags.LayoutHideNavigation;
uiOptions |= (int)SystemUiFlags.LayoutFullscreen;
uiOptions |= (int)SystemUiFlags.LowProfile;
uiOptions |= (int)SystemUiFlags.HideNavigation;
uiOptions |= (int)SystemUiFlags.Fullscreen;
uiOptions |= (int)SystemUiFlags.ImmersiveSticky;
this.Window.DecorView.SystemUiVisibility = (StatusBarVisibility)uiOptions;
}
catch (System.Exception Ex)
{
}
}
But there is no method in MainActivity.cs to override that is being called when user press "enter" key on keyboard. I have overridden more than 200 methods to check it. Then in Xamarin.Forms in code behind I have event:
private void Entry_Unfocused(object sender, FocusEventArgs e)
{
DependencyService.Get<ISoftwareButtons>().HideSoftwareMenuBars();
}
Then by calling dependency interface, here I have 2 errors:
[assembly: Dependency(typeof(SoftwareButtonsHandler))]
namespace Channel.Droid.DependencyHandlers
{
public class SoftwareButtonsHandler
{
private void HideSoftwareMenuBars()
{
try
{
int uiOptions = (int) Window.DecorView.SystemUiVisibility;
uiOptions |= (int)SystemUiFlags.LayoutStable;
uiOptions |= (int)SystemUiFlags.LayoutHideNavigation;
uiOptions |= (int)SystemUiFlags.LayoutFullscreen;
uiOptions |= (int)SystemUiFlags.LowProfile;
uiOptions |= (int)SystemUiFlags.HideNavigation;
uiOptions |= (int)SystemUiFlags.Fullscreen;
uiOptions |= (int)SystemUiFlags.ImmersiveSticky;
this.Window.DecorView.SystemUiVisibility = (StatusBarVisibility)uiOptions;
}
catch (System.Exception Ex)
{
}
}
}
}
The problem is that "Window.Devorview" has errors:
"Abstract base class for a top-level window look and behaviour policy.
An object reference is required for the non-static field, method, or
property 'Window.DecorView;"
and "this.Window"
"SoftwareButtonsHandler' does not contain definition for 'Window' and
no accessible extension method 'Window' accepting a first argument of
type 'SoftwareButtonsHandler' could be found (are you missing a using
directive or an assembly reference?"
Is there a way to call MainActivity.cs's method from another class or get necessary "Window" in dependency handler (that is accessible only in MainActivity.cs) ?

Answer 1

You can create a MainActivityInstance in MainActivity and set it like MainActivityInstance = this in OnCreate:
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
public static MainActivity MainActivityInstance { get; private set; }
protected override void OnCreate(Bundle savedInstanceState)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(savedInstanceState);
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
MainActivityInstance = this;
LoadApplication(new App());
}
}
Then you can get the MainActivity in dependency interface:
public class SoftwareButtonsHandler : ISoftwareButtons
{
void ISoftwareButtons.HideSoftwareMenuBars()
{
try
{
int uiOptions = (int)MainActivity.MainActivityInstance.Window.DecorView.SystemUiVisibility;
uiOptions |= (int)SystemUiFlags.LayoutStable;
uiOptions |= (int)SystemUiFlags.LayoutHideNavigation;
uiOptions |= (int)SystemUiFlags.LayoutFullscreen;
uiOptions |= (int)SystemUiFlags.LowProfile;
uiOptions |= (int)SystemUiFlags.HideNavigation;
uiOptions |= (int)SystemUiFlags.Fullscreen;
uiOptions |= (int)SystemUiFlags.ImmersiveSticky;
MainActivity.MainActivityInstance.Window.DecorView.SystemUiVisibility = (StatusBarVisibility)uiOptions;
}
catch (System.Exception Ex)
{
}
}
}

Answer 2

You can make a static reference to MainActivity that will be accessible everywhere, or you may use CurrentActivity plugin.