摇杆Joystick

# 效果

 

# dynamic动态摇杆就是在哪里按下，摇杆就出现在那里。

using UnityEngine;
using UnityEngine.Events;
using UnityEngine.EventSystems;

public class Joystick : MonoBehaviour, IPointerDownHandler, IPointerUpHandler, IDragHandler
{
    public class JoystickEvent : UnityEvent<Joystick> { }

    public JoystickEvent OnJoystickPointerDown = new JoystickEvent(); //摇杆被按下事件
    public JoystickEvent OnJoystickPointerUp = new JoystickEvent(); //摇杆被抬起事件
    public JoystickEvent OnJoystickValueChanged = new JoystickEvent();


    [Range(20, 100)]
    public float radius = 50;

    public Transform background;
    public Transform stick;
    public bool dynamic; //是否为动态摇杆

    private RectTransform _cachedRectTransform;
    private RectTransform _backgroundRectTransform;

    private Vector3 _backgroundInitLPosition;
    private int _pointerId = int.MinValue;

    void Start()
    {
        _backgroundInitLPosition = background.localPosition;
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        if (_pointerId != int.MinValue) return;
        _pointerId = eventData.pointerId;
        if (dynamic)
        {
            if (null == _cachedRectTransform)
                _cachedRectTransform = (RectTransform)transform;
            if (RectTransformUtility.ScreenPointToLocalPointInRectangle(_cachedRectTransform, eventData.position, eventData.pressEventCamera, out var localPos))
            {
                background.localPosition = localPos;
            }
        }
        else
        {
            UpdateStickPos(eventData);
        }

        OnJoystickPointerDown.Invoke(this);
    }

    public void OnDrag(PointerEventData eventData)
    {
        if (_pointerId != eventData.pointerId) return;
        //var deltaPos = eventData.position - eventData.pressPosition; //都是屏幕坐标
        UpdateStickPos(eventData);
    }


    void UpdateStickPos(PointerEventData eventData)
    {
        if (null == _backgroundRectTransform)
            _backgroundRectTransform = (RectTransform)background;

        if (RectTransformUtility.ScreenPointToLocalPointInRectangle(_backgroundRectTransform, eventData.position, eventData.pressEventCamera, out var localPos))
        {
            if (localPos.magnitude >= radius)
            {
                localPos.Normalize();
                localPos *= radius;
            }
            stick.localPosition = localPos;
        }
    }

    void Update()
    {
        if (int.MaxValue != _pointerId)
        {
            OnJoystickValueChanged.Invoke(this);
        }
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        if (_pointerId == eventData.pointerId)
        {
            _pointerId = int.MinValue;
            background.localPosition = _backgroundInitLPosition;
            stick.localPosition = Vector3.zero;
            OnJoystickPointerUp.Invoke(this);
        }
    }

    public float GetStickAngle()
    {
        var lpos = stick.localPosition;
        var angle = Mathf.Atan2(lpos.y, lpos.x) * Mathf.Rad2Deg;
        return angle;
    }

}