using UnityEngine;

using System.Collections;

using UnityEngine.UI;

public delegate void JoystickMoveDelegate(JoystickData data);

public class Joystick : MonoBehaviour {

    public GameObject joystickUI;                   //摇杆整体UI,方便Active

    public RectTransform joystickCenter;            //摇杆重心

    public RectTransform joystickBackground;        //摇杆背景

    private float halfScreenWidth;

    private float halfScreenHeight;

    private RectTransform joystickRect;

    private float radius;

    private Vector3 lastMousePosition;

    public static event JoystickMoveDelegate JoystickMoveEvent;

    // Use this for initialization

    void Start () {

        halfScreenWidth = Screen.width / 2;

        halfScreenHeight = Screen.height / 2;

        joystickRect = this.gameObject.GetComponent<RectTransform>();

        radius = 71;

    }

    // Update is called once per frame

    void Update () {

        JoystickController();

    }

    public void JoystickController()

    {

        //鼠标一直按下

        if (Input.GetMouseButton(0))

        {

            float distance = Vector2.Distance(new Vector2(Input.mousePosition.x, Input.mousePosition.y), joystickRect.anchoredPosition);

            if (distance < radius)

            {

                //当距离小于半径就开始移动 摇杆重心

                joystickCenter.anchoredPosition = new Vector2(Input.mousePosition.x - joystickRect.anchoredPosition.x, Input.mousePosition.y - joystickRect.anchoredPosition.y);

            }

            else

            {

                //求圆上的一点：(目标点-原点) * 半径/原点到目标点的距离

                Vector2 endPosition = (new Vector2(Input.mousePosition.x, Input.mousePosition.y) - joystickRect.anchoredPosition) * radius / distance;

                joystickCenter.anchoredPosition = endPosition;

            }

            if (JoystickMoveEvent != null)

            {

                JoystickMoveEvent(new JoystickData() { x = joystickCenter.anchoredPosition.x - joystickBackground.anchoredPosition.x, y = joystickCenter.anchoredPosition.y - joystickBackground.anchoredPosition.y });

            }

        }

        //鼠标按下

        if (Input.GetMouseButtonDown(0))

        {

            this.joystickUI.SetActive(true);

            //鼠标单击左边屏幕

            if (Input.mousePosition.x < halfScreenWidth)

            {

                joystickRect.anchoredPosition = Input.mousePosition;

            }

            //鼠标单击右边屏幕

            if (Input.mousePosition.x >= halfScreenWidth)

            {

                // Debug.Log("鼠标单击右边");

            }

        }

        //鼠标释放的时候

        if (Input.GetMouseButtonUp(0))

        {

            this.joystickUI.SetActive(false);

        }

    }

}

public class JoystickData

{

    public float x;

    public float y;

}