Register Call Back Question

Hello.
I've gotten stuck with registering callback functions for buttons in the run time (I'm seeing topics relative to the Editor, but hey aren't working).

I'm using Unity 2020.1.0b3.3385
I created a Panel Object and attached a script to it. (In the Panel Object, it has both a PanelRenderer and an EventSystem component, based on feedback I've seen elsewhere).

I'm able to get the UXML UI to render and can access its elements via C# script, but I can't get the callbacks registration to work. I'd appreciate any advice.

Code (CSharp):

1.  
2. using UnityEngine;
3. using UnityEngine.UIElements;
4. using Unity.UIElements.Runtime;
5.  
6.  
7. public class SamplePanelScript : MonoBehaviour
8. {
9.     public GameObject thePanel;
10.     private VisualElement theVisualTree;
11.  
12.     // Start is called before the first frame update
13.     void Start()
14.     {
15.         PanelRenderer theRenderer = thePanel.GetComponent<PanelRenderer>();
16.         theVisualTree = theRenderer.visualTree;
17.        
18.         Button button = theVisualTree.Q<Button>("test-button");
19.         //This debug statement works
20.         Debug.Log("button.text: " + button.text);
21.  
22.         button.RegisterCallback<MouseDownEvent> (OnMouseDown);                
23.     }
24.  
25.     void OnMouseDown(MouseDownEvent e)
26.     {
27.         //This debug is not getting fired when I click the button during play mode
28.         Debug.Log("OnMouseDown called");
29.     }
30. }
31.  

I originally had this in OnEnable, but theRenderer.visualTree property was null in that context.

Thank you.

 

I think it uses a 'clicked' callback inside the Button class. So something like

button.clicked += OnMouseDown;

.

 

The Developer Guide specifically mentions Register Call Back:

https://docs.unity3d.com/Manual/UIE-Events-Handling.html''

So, not sure what's wrong here.

 

uMathieu,
Thank you for the pointer. I never would have figured that out. I modified my code to per your suggestion, and it didn't originally work. However, I figured it out. I needed to get a reference to the right visual tree from the PanelRenderer.

Code (CSharp):

1.  
2.  
3. void OnEnable()
4.     {
5.         PanelRenderer theRenderer = thePanel.GetComponent<PanelRenderer>();
6.         if (theRenderer.visualTree == null)
7.         {
8.             theRenderer.RecreateUIFromUxml();
9.         }
10.         theVisualTree = theRenderer.visualTree;
11.  
12.  
13.  
14.         Button button = theVisualTree.Q<Button>("test-button");
15.         //This debug statement works
16.         Debug.Log("button.text: " + button.text);
17.  
18.         button.clicked += () => Debug.Log("Button clicked");
19.  
20.     }
21.  
22.  

 

MouseUpEvent works for buttons, MouseDownEvent don't. Using Version 1.0.0-preview.14 - March 30, 2021.

 

Is there a work around for capturing button click on mouse down?

 

I'm using Unity 2021.1.21f1. I have UI Builder & UI Toolkit versions 1.0.0-preview.17 installed. I have the Input System version 1.0.2 installed. When I listen for clicked events on a button created in UI Builder, it does not fire when running in Play mode with a UI Document. I've had to resort to listening to MouseDownEvent. Is it possible there's a bug with the Input System Event System (UI Toolkit) script?