using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Arrow : MonoBehaviour
{
    public Vector2 StartPoint;
    private Vector2 EndingPoint;
    private RectTransform arrow;

    private float ArrowLength;
    private float ArrowTheta;
    private Vector2 ArrowPostion;


    // Start is called before the first frame update
    void Start()
    {
        arrow = transform.GetComponent<RectTransform>();
    }

    // Update is called once per frame
    void Update()
    {
        //计算变量
        EndingPoint = Input.mousePosition - new Vector3(1280.0f, 720.0f, 0.0f);//和分辨率有关，位置在game画面中以左下角为原点，而我们设计画面则以中心原点
        ArrowLength = Mathf.Sqrt((EndingPoint.x - StartPoint.x) * (EndingPoint.x - StartPoint.x) + (EndingPoint.y - StartPoint.y) * (EndingPoint.y - StartPoint.y)) - 60;
        ArrowPostion = new Vector2((EndingPoint.x + StartPoint.x) / 2, (EndingPoint.y + StartPoint.y) / 2);
        ArrowTheta = Mathf.Atan2((EndingPoint.y - StartPoint.y), (EndingPoint.x - StartPoint.x));
        //赋值
        arrow.localPosition = ArrowPostion;
        arrow.sizeDelta = new Vector2(ArrowLength, arrow.sizeDelta.y);
        arrow.localEulerAngles = new Vector3(0.0f, 0.0f, ArrowTheta * 180 / Mathf.PI);
    }
    public void SetStartPoint(Vector2 _startPoint)
    {
        StartPoint = _startPoint - new Vector2(1280.0f, 720.0f);
    }
}