UI toolkit Button can't be queried

Unity Engine
1

I am trying to create a editor Tool for testings of my dialog system, and I need to assign a button to test this functions, but for some reason I cant assign an function for the clicked event.

The createGUI function looks like this

    public void CreateGUI()
    {

        VisualElement root = rootVisualElement;


        TextInput = rootVisualElement.Q<TextField>("TextData");
        DialogData = rootVisualElement.Q<ObjectField>("DialogSO");
        BotaoTrigger = rootVisualElement.Q<Button>("Ativador");
        DialogData.RegisterValueChangedCallback(Value => { dialog = (DialogDataSO)Value.newValue; });
        //BotaoTrigger.RegisterCallback<>
        BotaoTrigger.clicked += TypeTest;

        // Instantiate UXML
        VisualElement labelFromUXML = m_VisualTreeAsset.Instantiate();
        root.Add(labelFromUXML);
       
    }

In Visual Studio, it doesnā€™t show any type of errors, But after saving it and Unity Editor Compile the code, It returns a NullReferenceException, even when all the names are correct.

I really thank the help so far if itā€™s not a bug

2

Thereā€™s only one answer here: fix this first.

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:

  • Identify what is null ā† any other action taken before this step is WASTED TIME
  • Identify why it is null
  • Fix that

If the nullref isnā€™t in your code, then move onto other checks to ensure youā€™re using the library correctly.

3

The Null Reference is in the line that assigns the function do the clicked event.

This line delivers the button object with the button visual in the UIDocument.

BotaoTrigger = rootVisualElement.Q<Button>("Ativador");

And this live subscribe the function to the Clicked event of said button

BotaoTrigger.clicked += TypeTest;

The string does not have any typo or anything like it. It just send a null reference, there isnā€™t any reference to another script

4

If you just rootVisualElement.Q<Button>(); do you get any results?

1 Like
5

Since the default parameter for the Q() is null, it returns the same error in the same line (BotaoTrigger.clicked += TypeTest; )

6

So are there any UI elements actually generated at this point? It sounds like thereā€™s just a root visual element and nothing else.

1 Like
7

Thatā€™s why I believe is actually a Bug, because I made the UI Button In the UI document already, but aparently it wasnā€™t able to identify it, even with the right name

8

Right but has the button actually been added?

If I create I visual tree asset with a button called ā€œTestButtonā€, and write the following code:

using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;
using UnityEditor.UIElements;

public class EditorWindowTest : EditorWindow
{
    [MenuItem("Testing/EditorWindowTest")]
    public static void ShowExample()
    {
        EditorWindowTest wnd = GetWindow<EditorWindowTest>();
        wnd.titleContent = new GUIContent("EditorWindowTest");
    }

    public void CreateGUI()
    {
        VisualElement root = rootVisualElement;

        var visualAsset = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>("PathToAsset");
        VisualElement treeRoot = visualAsset.Instantiate();
        root.Add(treeRoot);

        Button button = treeRoot.Q<Button>("TestButton");
        button.clicked += () => Debug.Log("Working!");
    }
}

It works totally fine:

8709867--1176813--upload_2023-1-6_23-18-47.png
8709867--1176813--upload_2023-1-6_23-18-47.png1065Ɨ180 17.1 KB

Notably I have to load and add the visual tree first before I can query the button. They arenā€™t magically tied together.

1 Like
9

Thanks for the answer, Since the other elements seemed to work correctly (Or I was thinking too much in the old editor window way to do it), then I believed there was a bug actualy. Now it seems to work fine (Good that I know that I need to look better at the other elements as well).