BetterToggle.cs

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace Bombardel
{
	public class BetterToggle : MonoBehaviour, IPointerEnterHandler, IPointerExitHandler, IPointerClickHandler, IPointerDownHandler, IPointerUpHandler
	{

		[Header("General")]
		public Image targetGraphic;
		public BetterToggleGroup toggleGroup;
		public bool disabled = false;
		public bool isOn = false;

		[Header("Sprite Swap")]
		public bool spriteSwap;

		[ConditionalField("spriteSwap")]
		public Sprite normalSprite;
		[ConditionalField("spriteSwap")]
		public Sprite highlightedSprite;
		[ConditionalField("spriteSwap")]
		public Sprite pressedSprite;
		[ConditionalField("spriteSwap")]
		public Sprite selectedSprite;
		[ConditionalField("spriteSwap")]
		public Sprite disabledSprite;

		[Header("Color Tint")]
		public bool colorTint;

		[ConditionalField("colorTint")]
		public Color normalColor = Color.white;
		[ConditionalField("colorTint")]
		public Color highlightedColor = Color.white;
		[ConditionalField("colorTint")]
		public Color pressedColor = Color.white;
		[ConditionalField("colorTint")]
		public Color selectedColor = Color.white;
		[ConditionalField("colorTint")]
		public Color disabledColor = Color.white;

		private bool pressed = false;
		private bool highlighted = false;

		public void Awake()
		{
			UpdateState();
			if (toggleGroup != null) toggleGroup.RegisterToggle(this);

			if (normalSprite == null) normalSprite = targetGraphic.sprite;
		}

		public void OnPointerEnter(PointerEventData eventData)
		{
			highlighted = true;
			UpdateState();
		}

		public void OnPointerExit(PointerEventData eventData)
		{
			highlighted = false;
			UpdateState();
		}

		public void OnPointerDown(PointerEventData eventData)
		{
			pressed = true;
			UpdateState();
		}

		public void OnPointerUp(PointerEventData eventData)
		{
			pressed = false;
			UpdateState();
		}

		public void OnPointerClick(PointerEventData eventData)
		{
			if (toggleGroup != null)
			{
				if (isOn) toggleGroup.ActivateToggle(null);
				else toggleGroup.ActivateToggle(this);
			}
			else
			{
				if (isOn) DisableToggle();
				else EnableToggle();

			}
		}

		private Sprite NullCoalesce(Sprite first, Sprite fallback)
		{
			return first != null ? first : fallback;
		}

		private void UpdateState()
		{
			// simplest use case
			if (disabled)
			{
				if (spriteSwap) targetGraphic.sprite = NullCoalesce(disabledSprite, normalSprite);
				if (colorTint) targetGraphic.color = disabledColor;
				return;
			}

			// selected
			if (isOn)
			{
				if (spriteSwap) targetGraphic.sprite = NullCoalesce(selectedSprite, normalSprite);
				if (colorTint) targetGraphic.color = selectedColor;
				return;
			}

			// pressed
			if (pressed)
			{
				if (spriteSwap) targetGraphic.sprite = NullCoalesce(pressedSprite, NullCoalesce(selectedSprite, normalSprite));
				if (colorTint) targetGraphic.color = pressedColor;
				return;
			}

			// we are highlighted
			if (highlighted)
			{
				if (spriteSwap) targetGraphic.sprite = NullCoalesce(highlightedSprite, normalSprite);
				if (colorTint) targetGraphic.color = highlightedColor;
				return;
			}

			if (spriteSwap) targetGraphic.sprite = normalSprite;
			if (colorTint) targetGraphic.color = normalColor;
		}

		public void EnableToggle()
		{
			isOn = true;
			UpdateState();
		}

		public void DisableToggle()
		{
			isOn = false;
			UpdateState();
		}

		public void OnDestroy()
		{
			if (toggleGroup != null) toggleGroup.UnregisterToggle(this);
		}
	}
}

BetterToggleGroup.cs

using System.Collections.Generic;
using UnityEngine;

namespace Bombardel
{
	public class BetterToggleGroup : MonoBehaviour
	{
		public bool allowSwitchOff = false;

		[ConditionalField("allowSwitchOff", true)]
		public BetterToggle defaultToggleAllOff;


		private List<BetterToggle> toggles = new List<BetterToggle>();

		private BetterToggle activeToggle = null;


		public void RegisterToggle(BetterToggle toggle)
		{
			toggles.Add(toggle);
		}

		public void UnregisterToggle(BetterToggle toggle)
		{
			toggles.Remove(toggle);
		}

		public void Update()
		{
			if (activeToggle == null && !allowSwitchOff)
			{
				if (defaultToggleAllOff != null) ActivateToggle(defaultToggleAllOff);
				else if (toggles.Count > 0) ActivateToggle(toggles[0]);
			}
		}

		public void ActivateToggle(BetterToggle toggle)
		{
			if (activeToggle == toggle && !allowSwitchOff) return; // can't disable yourself if you can't switch everything off
			if (activeToggle != null) activeToggle.DisableToggle();
			activeToggle = toggle;
			if (activeToggle != null) activeToggle.EnableToggle();
		}

	}
}