摇杆

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
/// <summary>
/// 摇杆
/// </summary>
public class Rocker : MonoBehaviour,IDragHandler,IEndDragHandler
{
    public static Vector2 offset;//保存移动距离和方向
    public RectTransform bar;//小圆
    public RectTransform rocker;//大圆
    public float r;//大圆半径
    public float r1;//小圆半径

    public void OnDrag(PointerEventData eventData)
    {
        Vector2 pos = eventData.position - rocker.anchoredPosition;
        bar.anchoredPosition = Vector2.ClampMagnitude(pos,r-r1);
        offset = bar.anchoredPosition / r;
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        bar.anchoredPosition = Vector2.zero;
        offset = Vector2.zero;
    }

    // Start is called before the first frame update
    void Start()
    {
        r = rocker.rect.width < rocker.rect.height ? rocker.rect.width / 2 : rocker.rect.height / 2;
        r1 = bar.rect.width < bar.rect.height ? bar.rect.width/2 : bar.rect.height/2;
    }
}