How to have a callback when a toggle is clicked in a toggle group?

Question

I want a callback funcion to be called when one of my toggles in a toggle group is clicked.

I thought about making something like this

foreach (Toggle t in toggles) { t.onValueChanged.AddListener(callback); }

but then the callback would be called twice, because one toggle was selected, and other was deselected.

Any ideas?

Answer 1

I made a class which inherits the ToggleGroup which has an OnChange event: https://gist.github.com/jmbeach/78c3e46669db89628fce#file-bettertogglegroup-cs

 using UnityEngine;
 using UnityEngine.UI;
 using System.Linq;
 
 public class BetterToggleGroup : ToggleGroup {
     public delegate void ChangedEventHandler(Toggle newActive);
 
     public event ChangedEventHandler OnChange;
     public void Start() {
         foreach (Transform transformToggle in gameObject.transform) {
             var toggle = transformToggle.gameObject.GetComponent<Toggle>();
             toggle.onValueChanged.AddListener((isSelected) => {
                 if (!isSelected) {
                     return;
                 }
                 var activeToggle = Active();
                 DoOnChange(activeToggle);
             });
         }
     }
     public Toggle Active() {
         return ActiveToggles().FirstOrDefault();
     }
 
     protected virtual void DoOnChange(Toggle newactive)
     {
         var handler = OnChange;
         if (handler != null) handler(newactive);
     }
 }

Add the above class to your project and replace the ToggleGroup script in the inspector with it. The class requires that all of the ToggleGroup's Toggles are children of it: Inspector view of toggle group To listen to the event, from another script use the following code:

 TglGroup = GameObject.Find("Toggle Group Name").GetComponent<BetterToggleGroup>();
 TglGroup.OnChange += TglGroup_OnChange;
 //...
 void TglGroup_OnChange(Toggle newActive)
 {
   Debug.Log(string.Format("Toggle {0} selected",newActive.name));
 }

Answer 2

@thatshowifeel had a good answer. Here's a slightly improved, more modern version:

 using System.Linq;
 using UnityEngine;
 using UnityEngine.Events;
 using UnityEngine.UI;
 
 [RequireComponent(typeof(ToggleGroup))]
 public class EventToggleGroup : MonoBehaviour
 {
     [System.Serializable]
     public class ToggleEvent : UnityEvent<Toggle> { }
 
     [SerializeField]
     public ToggleEvent onActiveTogglesChanged;
 
     [SerializeField]
     private Toggle[] _toggles;
 
     private ToggleGroup _toggleGroup;
 
     private void Awake()
     {
         _toggleGroup = GetComponent<ToggleGroup>();
     }
 
     // Start is called before the first frame update
     void OnEnable()
     {
         foreach (Toggle toggle in _toggles)
         {
             if (toggle.group != null && toggle.group != _toggleGroup)
             {
                 Debug.LogError($"EventToggleGroup is trying to register a Toggle that is a member of another group.");
             }
             toggle.group = _toggleGroup;
             toggle.onValueChanged.AddListener(HandleToggleValueChanged);
         }
     }
 
     void HandleToggleValueChanged(bool isOn)
     {
         if (isOn)
         {
             onActiveTogglesChanged?.Invoke(_toggleGroup.ActiveToggles().FirstOrDefault());
         }
     }
 
     void OnDisable()
     {
         foreach (Toggle toggle in _toggleGroup.ActiveToggles())
         {
             toggle.onValueChanged.RemoveListener(HandleToggleValueChanged);
             toggle.group = null;
         }
     }
 }

To use:

1) Add EventToggleGroup as a sibling of ToggleGroup.
2) Drag Toggle into EventToggleGroup.toggles.
3) Add something to listen to onActiveToggleChanged. Note: It may return null if no toggles are selected!

alt text

Changes:

*Rather than assuming the Toggles are children of the ToggleGroup transform you must explicitly specify the toggles. This allows you to put the ToggleGroup/EventToggleGroup wherever you want in the GameObject hierarchy.

*It is not necessary to specify the "group" on the individual Toggle components anymore. (Note: This does allow a toggle to be a member of multiple EventToggleGroups! Don't do this.)

*Rather than deriving from ToggleGroup, EventToggleGroup is a sibling component of ToggleGroup. This conforms to the Entity/Component model better.

*Rather than raising a C# event, it raises a UnityEvent which allows us to hook up event listeners in the UnityEditor AND code.

Answer 3

Answer by MarcoSoldati · May 21, 2021 at 08:48 AM

Great solution. Thanks. I added a small function to set one option to 'on' and disable the others (useful for radio buttons).

     /**
      * Programmatically set a toggle to on (and set all others to off).
      */
     public void SetToggle(Toggle toggle)
     {
         foreach (Toggle t in Toggles)
         {
             bool isOn = toggle == t;
             t.isOn = isOn;
             Debug.Log(("setting " + t.name + " to " + isOn));
         }
     }

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MarcoSoldati · May 21, 2021 at 08:51 AM 0

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@DoomGoober line 49 it would be more failure safe to use _toggles instead of ActiveToggles()

How to have a callback when a toggle is clicked in a toggle group?

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