Change StateTriggerBase OnAttached and OnDetached methods to be public (#9888)

* Change OnAttached and OnDetached to be public

* Fixed build error

* Removed unnecessary virtual methods

* Fixed build error

Xamarin.Forms.Core/AdaptiveTrigger.cs

@@ -39,7 +39,7 @@ namespace Xamarin.Forms
 			((AdaptiveTrigger)bindable).UpdateState();
 		}
 
-		internal override void OnAttached()
+		protected override void OnAttached()
 		{
 			base.OnAttached();
 
@@ -50,7 +50,7 @@ namespace Xamarin.Forms
 			}
 		}
 
-		internal override void OnDetached()
+		protected override void OnDetached()
 		{
 			base.OnDetached();
 

Xamarin.Forms.Core/CompareStateTrigger.cs

@@ -40,7 +40,7 @@ namespace Xamarin.Forms
 			((CompareStateTrigger)bindable).UpdateState();
 		}
 
-		internal override void OnAttached()
+		protected override void OnAttached()
 		{
 			base.OnAttached();
 			UpdateState();

Xamarin.Forms.Core/OrientationStateTrigger.cs

@@ -26,7 +26,7 @@ namespace Xamarin.Forms
 			((OrientationStateTrigger)bindable).UpdateState();
 		}
 
-		internal override void OnAttached()
+		protected override void OnAttached()
 		{
 			base.OnAttached();
 
@@ -37,7 +37,7 @@ namespace Xamarin.Forms
 			}
 		}
 
-		internal override void OnDetached()
+		protected override void OnDetached()
 		{
 			base.OnDetached();
 

Xamarin.Forms.Core/StateTrigger.cs

@@ -20,7 +20,7 @@
 			}
 		}
 
-		internal override void OnAttached()
+		protected override void OnAttached()
 		{
 			base.OnAttached();
 			UpdateState();

Xamarin.Forms.Core/StateTriggerBase.cs

@@ -27,6 +27,8 @@ namespace Xamarin.Forms
 
 		internal VisualState VisualState { get; set; }
 
+		public bool IsAttached { get; private set; }
+
 		protected void SetActive(bool active)
 		{
 			IsActive = active;
@@ -34,14 +36,30 @@ namespace Xamarin.Forms
 			VisualState?.VisualStateGroup?.UpdateStateTriggers();
 		}
 
-		internal virtual void OnAttached()
+		protected virtual void OnAttached()
 		{
 
 		}
 
-		internal virtual void OnDetached()
+		protected virtual void OnDetached()
 		{
 
 		}
+
+		internal void SendAttached()
+		{
+			if (IsAttached)
+				return;
+			OnAttached();
+			IsAttached = true;
+		}
+
+		internal void SendDetached()
+		{
+			if (!IsAttached)
+				return;
+			OnDetached();
+			IsAttached = false;
+		}
 	}
 }

Xamarin.Forms.Core/VisualElement.cs

@@ -847,9 +847,9 @@ namespace Xamarin.Forms
 					foreach (var stateTrigger in state.StateTriggers)
 					{
 						if(attach)
-							stateTrigger.OnAttached();
+							stateTrigger.SendAttached();
 						else
-							stateTrigger.OnDetached();
+							stateTrigger.SendDetached();
 					}
 		}
 

Xamarin.Forms.DualScreen/SpanModeStateTrigger.shared.cs

@@ -41,7 +41,7 @@ namespace Xamarin.Forms.DualScreen
 			_info = new DualScreenInfo(_visualElement);
 		}
 
-		internal override void OnAttached()
+		protected override void OnAttached()
 		{
 			base.OnAttached();
 
@@ -55,7 +55,7 @@ namespace Xamarin.Forms.DualScreen
 			}
 		}
 
-		internal override void OnDetached()
+		protected override void OnDetached()
 		{
 			base.OnDetached();
 

Xamarin.Forms.DualScreen/WindowSpanModeStateTrigger.shared.cs

@@ -24,7 +24,7 @@ namespace Xamarin.Forms.DualScreen
 			((WindowSpanModeStateTrigger)bindable).UpdateState();
 		}
 
-		internal override void OnAttached()
+		protected override void OnAttached()
 		{
 			base.OnAttached();
 
@@ -35,7 +35,7 @@ namespace Xamarin.Forms.DualScreen
 			}
 		}
 
-		internal override void OnDetached()
+		protected override void OnDetached()
 		{
 			base.OnDetached();