Unity 获取鼠标滚轮信息的一些方法

Unity获取鼠标滚轮信息有以下一些方法：

1、使用Input.GetAxis("Mouse ScrollWheel")来获取鼠标滚轮的信息，如：

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 //法一：

        float scrollWheelInput = Input.GetAxis("Mouse ScrollWheel");

        if (scrollWheelInput > 0f)
        {
            Debug.Log("向上滚动鼠标滚轮");
        }
        else if (scrollWheelInput < 0f)
        {
            Debug.Log("向下滚动鼠标滚轮");
        }

2、使用mouseScrollDelta变量，如：

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 //法二：

        float scrollWheelInput1 = Input.mouseScrollDelta.y;

        if (scrollWheelInput1 > 0f)
        {
            Debug.Log("向上滚动鼠标滚轮");
        }
        else if (scrollWheelInput1 < 0f)
        {
            Debug.Log("向下滚动鼠标滚轮");
        }

3、假如我们想只在UGUI上滚动鼠标滚轮才获取信息，可以使用一个专门的接口：IScrollHandler，实现的方法是：

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    public void OnScroll(PointerEventData eventData)
    {
        throw new System.NotImplementedException();
    }

该函数的参数PointerEventData具有很多相关的数据：

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    public class PointerEventData : BaseEventData
    {
        public List<GameObject> hovered;

        public PointerEventData(EventSystem eventSystem);

        public bool useDragThreshold { get; set; }
        public bool dragging { get; set; }
        public InputButton button { get; set; }
        public float pressure { get; set; }
        public float tangentialPressure { get; set; }
        public float altitudeAngle { get; set; }
        public float azimuthAngle { get; set; }
        public float twist { get; set; }
        public Vector2 radius { get; set; }
        public Vector2 radiusVariance { get; set; }
        public bool fullyExited { get; set; }
        public bool reentered { get; set; }
        public Camera enterEventCamera { get; }
        public Camera pressEventCamera { get; }
        public GameObject pointerPress { get; set; }
        public Vector2 scrollDelta { get; set; }
        public int clickCount { get; set; }
        public float clickTime { get; set; }
        [Obsolete("Use either pointerCurrentRaycast.worldNormal or pointerPressRaycast.worldNormal")]
        public Vector3 worldNormal { get; set; }
        public GameObject pointerEnter { get; set; }
        public GameObject lastPress { get; }
        public GameObject rawPointerPress { get; set; }
        public GameObject pointerDrag { get; set; }
        public RaycastResult pointerCurrentRaycast { get; set; }
        public RaycastResult pointerPressRaycast { get; set; }
        public GameObject pointerClick { get; set; }
        public int pointerId { get; set; }
        public Vector2 position { get; set; }
        public Vector2 delta { get; set; }
        public Vector2 pressPosition { get; set; }
        [Obsolete("Use either pointerCurrentRaycast.worldPosition or pointerPressRaycast.worldPosition")]
        public Vector3 worldPosition { get; set; }
        public bool eligibleForClick { get; set; }

        public bool IsPointerMoving();
        public bool IsScrolling();
        public override string ToString();

        public enum InputButton
        {
            Left = 0,
            Right = 1,
            Middle = 2
        }
        public enum FramePressState
        {
            Pressed = 0,
            Released = 1,
            PressedAndReleased = 2,
            NotChanged = 3
        }
    }

其中，scrollDelta属性与上面方法1/2的数据一样。所以我们可以这样实现方法以获取滚轮信息：

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//法三：
    public void OnScroll(PointerEventData eventData)
    {
        if (eventData.scrollDelta.y > 0f)
        {
            Debug.Log("向上滚动鼠标滚轮");
        }
        else if (eventData.scrollDelta.y < 0f)
        {
            Debug.Log("向下滚动鼠标滚轮");
        }
    }

使用法三，需要注意的是：只有我们把控制脚本放在相应的UGUI物体上才有效，或者放在Canvas下对所有UGUI有效。

但使用该方法的好处是：我们可以通过UGUI实现在指定获取滚轮信息。