Property drawer / attribute can't being serialized

Unity Engine
1

Hello everyone !

I’m trying to code a property attribute [ InputeName ] that allow to get all Project Settings input axes name into a dropdown list in the inspector to choose the value of componant field like the picture below showing it.

It work perfectly except one major problem… when I enter play mode or change scene, dropdown list are reset to the first element of the list ( horizontal). I think it’s because something isn’t serialized but I don’t know what and why. I’m totally new at editor coding and after research on the net I found people with the same problem as me but the solution provided don’t work for me. This is mu code :

using UnityEngine;

public class InputNameAttribute : PropertyAttribute
{
    [SerializeField]
    public string inputName;
  
}

-----------------------------------------------
-----------------------------------------------

using UnityEditor;
using UnityEngine;

[CustomPropertyDrawer(typeof(InputNameAttribute))]
public class InputNameDrawer : PropertyDrawer
{
    private int index = 0;
    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        InputNameAttribute inputNameAttribute = attribute as InputNameAttribute;
        if (!property.propertyType.Equals(SerializedPropertyType.String))
        {
            EditorGUI.LabelField(position, label.text, "Input name attribute only work with string type.");
        }
        else
        {
            string[] list = GetInputManagerAxisList();
            index  = EditorGUI.Popup(position, property.displayName, index, list);
            property.stringValue = list[index];
        }

    }

    private string[] GetInputManagerAxisList()
    {
        SerializedObject inputManager = new SerializedObject(AssetDatabase.LoadAllAssetsAtPath("ProjectSettings/InputManager.asset")[0]);
        SerializedProperty axis = inputManager.FindProperty("m_Axes");
        string[] inputNameList = new string[axis.arraySize];
        int i = 0;
        foreach (SerializedProperty axe in axis)
        {
            inputNameList[i++] = axe.FindPropertyRelative("m_Name").stringValue;
        }

        return inputNameList;
    }
}
2 
private int index = 0;

You’re resetting the index every time you instantiate the property drawer. Instead of that you need to find the index that should be selected and pass that to Popup.

int index = Array.IndexOf(list, property.displayName);