Feedback [Event System] Cannot navigate in UI when FirstSelected is set through code in Update

Hi everyone,

It's the first time I implement two different menus which require individual FirstSelected gameobjects to be set in the EventSystem component. The logic is : If MenuLeft is opened, set someLeftSlot as FirstSelected. If MenuRight, set someRightSlot as FirstSelected.

After setting the code, I get the expected behaviour. When opening a given Menu, the correct slot is hightlighted. But then, I can no longer navigate in the displayed menu. When I press on my input to go down, the hightlight is stuck on the FirstSelection slot.



Just to understand the code : I call LeftSlot menu with PS4 L2 and RightSlot menu with PS4 R2. Those menus close when L2 or R2 is released. Once in the given menu, I set the FirstSelected to the first button of that slot in the Update method. I then want to navigate with the DPad vertical buttons.

Note : When I don't override the EventSystem's FirstSlected, I can acutally navigate in the individual menus, provided I first click on any button with the mouse. Also, I left all the booleans public for this thread's sake.


Event System setup



My script on Canvas


The code

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.EventSystems;
5.  
6. public class DoubleUINavigationTest : MonoBehaviour
7. {
8.     public EventSystem inputEventSystem;
9.  
10.     // Left & Right Slots.
11.     public GameObject leftSlot, rightSlot;
12.  
13.     // Left & Right FirstSelection for EventSystem.
14.     public GameObject leftFirstSelection, rightFirstSelection;
15.  
16.     // Left & Right Menus management.
17.     public bool OneMenuIsOpen; // Only one menu should be opened at a time.
18.     public bool leftInventory, rightInventory;
19.     public bool MenuLeft, MenuRight;
20.  
21.     // Input L2 & R2.
22.     private float inputL2, inputR2;
23.  
24.     // Input Dpad Vertical.
25.     private float inputDpad;
26.  
27.  
28.     private void Start()
29.     {
30.         // Initialize Menus and inventory togglers.
31.         OneMenuIsOpen = false;
32.         leftInventory = false;
33.         rightInventory = false;
34.         MenuLeft = false;
35.         MenuRight = false;
36.     }
37.  
38.  
39.     private void Update()
40.     {
41.         // Toggle between Menu.
42.         CurrentActiveMenu();
43.  
44.         // Set Input
45.         // leftInventory will be triggered by inputL2.
46.         // rightInventory will be triggered by inputR2.
47.         // inputDpad will be used to navigate in the different Menus.
48.         inputL2 = Input.GetAxis("PS4_L2");
49.         inputR2 = Input.GetAxis("PS4_R2");
50.         inputDpad = Input.GetAxis("Dpad_Vertical");
51.  
52.         if (inputL2 == 1 && !OneMenuIsOpen)
53.         {
54.             OneMenuIsOpen = leftInventory = true;
55.  
56.             // Change EventSystem firstSelected.
57.             ChangeESFirstSelection(leftFirstSelection);
58.         }
59.         else OneMenuIsOpen = leftInventory = false;
60.  
61.  
62.         if (inputR2 == 1 && !OneMenuIsOpen)
63.         {
64.             OneMenuIsOpen = rightInventory = true;
65.  
66.             // Change EventSystem firstSelected.
67.             ChangeESFirstSelection(rightFirstSelection);
68.         }
69.         else OneMenuIsOpen = rightInventory = false;
70.  
71.         // Activate/Desactivate Left or Right Slots
72.         ShowSelectedMenu(MenuLeft, leftSlot);
73.         ShowSelectedMenu(MenuRight, rightSlot);
74.     }
75.  
76.  
77.     // Method to Toggle between Menus --------------------------------
78.     // leftInventory will be triggered by PS4 L2.
79.     // rightInventory will be triggered by PS4 R2.
80.     // Note : In other scripts, only one menu will be called at a time
81.     // with the check bool OneMenuIsOpen.
82.     // ---------------------------------------------------------------
83.     private void CurrentActiveMenu()
84.     {
85.         if (leftInventory)
86.         {
87.             MenuLeft = true;
88.         }
89.         else MenuLeft = false;
90.  
91.         if (rightInventory)
92.         {
93.             MenuRight = true;
94.         }
95.         else MenuRight = false;
96.     }
97.  
98.  
99.     // ----------------------------------------------------------------
100.     // Method to Activate/Desactivate Left or Right Slots (gameobject)
101.     // depending on Menu activation condition.
102.     // ----------------------------------------------------------------
103.     private void ShowSelectedMenu(bool condition, GameObject selected)
104.     {
105.         // If condition is true, setActive(true).
106.         // Else desactivate the gameobject.
107.         selected.SetActive(condition);
108.     }
109.  
110.  
111.     // --------------------------------------------------------------------
112.     // Method to Change EventSystem firstSelected depending on opened Menu.
113.     // --------------------------------------------------------------------
114.     private void ChangeESFirstSelection(GameObject firstSelection)
115.     {
116.         inputEventSystem.SetSelectedGameObject(null);   // Hack to fix selection hightlight.
117.         inputEventSystem.SetSelectedGameObject(firstSelection);
118.         inputEventSystem.firstSelectedGameObject = firstSelection; // Without this line, the EventSystem FirstSelected field stays empty. Is this needed?
119.     }
120. }
121.  

// Edit : I saw that when I Debug.Log(inputEventSystem.alreadySelecting), it always returns false.


When L2 or R2 is pressed


Can anyone help me ? Many thanks.