Joystick

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class Joystick : MonoBehaviour, IDragHandler, IPointerDownHandler, IPointerUpHandler
{
    private const string HORIZONTAL = "Horizontal";
    private const string VERTICAL = "Vertical";

    [SerializeField] private RectTransform _joystick;
    public Vector2 InputVector { get; private set; }

    private RectTransform _background;

    private void Start()
    {
        _background = GetComponent<RectTransform>();
        _joystick = transform.GetChild(0).GetComponent<Image>().rectTransform;
    }

    public float Horizontal =>
        InputVector.x != 0
            ? InputVector.x
            : Input.GetAxis(HORIZONTAL);

    public float Vertical =>
        InputVector.y != 0
            ? InputVector.y
            : Input.GetAxis(VERTICAL);

    public virtual void OnPointerDown(PointerEventData eventData) => OnDrag(eventData);

    public virtual void OnPointerUp(PointerEventData eventData)
    {
        InputVector = Vector2.zero;
        _joystick.anchoredPosition = Vector2.zero;
    }

    public virtual void OnDrag(PointerEventData eventData)
    {
        Vector2 screenPoint = eventData.position;
        Camera eventCamera = eventData.pressEventCamera;

        bool inRectangle = InRectangle(_background, screenPoint, eventCamera, out Vector2 localPoint);

        if (inRectangle == false)
            return;

        localPoint.x /= SizeDelta.x;
        localPoint.y /= SizeDelta.x;

        InputVector = new Vector2(localPoint.x, localPoint.y).normalized;

        float x = InputVector.x * (SizeDelta.x / 2);
        float y = InputVector.y * (SizeDelta.y / 2);

        var position = new Vector2(x, y);

        _joystick.anchoredPosition = position;
    }

    private Vector2 SizeDelta => _background.sizeDelta;

    private static bool InRectangle
        (RectTransform rect, Vector2 screenPoint, Camera eventCamera, out Vector2 localPoint) =>
        RectTransformUtility.ScreenPointToLocalPointInRectangle(rect, screenPoint, eventCamera, out localPoint);
}