修复 Unity 中的 ScrollRect 多点触控？

Question

目前，ScrollRect 在移动设备上的多点触控方面存在极大缺陷。

如果你自己尝试一下，你会发现每当你将两根手指放在屏幕上时，内容就会跳来跳去，并产生一些意想不到的行为。

有什么解决办法吗？目前，this 是我找到的唯一解决方案，但在某些情况下它仍然存在问题，最重要的是，它不能确定屏幕上所有手指的平均输入位置（或 MultiTouchPosition）。

这是我修改后的来自UnityUIExtensions bitbucket 的MultiTouchScrollRect.cs 脚本，但每次我将下一个手指放在屏幕上时它都会跳转：

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class MultiTouchScrollRect : ScrollRect
{
    private int minimumTouchCount = 1, maximumTouchCount = 2, pointerId = -100;

    public Vector2 MultiTouchPosition
    {
        get
        {
            Vector2 position = Vector2.zero;
            for (int i = 0; i < Input.touchCount && i < maximumTouchCount; i++)
            {
                position += Input.touches[i].position;
            }
            position /= ((Input.touchCount <= maximumTouchCount) ? Input.touchCount : maximumTouchCount);
            return position;
        }
    }

    public override void OnBeginDrag(PointerEventData eventData)
    {
        if (Input.touchCount >= minimumTouchCount)
        {
            pointerId = eventData.pointerId;
            eventData.position = MultiTouchPosition;
            base.OnBeginDrag(eventData);
        }
    }
    public override void OnDrag(PointerEventData eventData)
    {
        if (Input.touchCount >= minimumTouchCount)
        {
            eventData.position = MultiTouchPosition;
            if (pointerId == eventData.pointerId)
            {
                base.OnDrag(eventData);
            }
        }
    }
    public override void OnEndDrag(PointerEventData eventData)
    {
        if (Input.touchCount >= minimumTouchCount)
        {
            pointerId = -100;
            eventData.position = MultiTouchPosition;
            base.OnEndDrag(eventData);
        }
    }
}

感谢您的宝贵时间！

Answer 1

对于那些感兴趣的人，这是我编写的扩展 ScrollRect 类，它解决了这个问题：

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace DanielLochner.Assets
{
    public class MultiTouchScrollRect : ScrollRect
    {
        #region Fields
        private int minimumTouchCount = 1, maximumTouchCount = 2, initialTouchCount = 0;
        #endregion

        #region Properties
        public Vector2 MultiTouchPosition
        {
            get
            {
                Vector2 position = Vector2.zero;
                for (int i = 0; i < Input.touchCount && i < maximumTouchCount; i++)
                {
                    position += Input.touches[i].position;
                }
                position /= ((Input.touchCount <= maximumTouchCount) ? Input.touchCount : maximumTouchCount);

                return position;
            }
        }
        #endregion

        #region Methods
        private void Update()
        {
            if (SystemInfo.deviceType == DeviceType.Handheld || UnityEditor.EditorApplication.isRemoteConnected)
            {
                if (Input.touchCount > 0)
                {
                    if (initialTouchCount == 0)
                    {
                        initialTouchCount = Input.touchCount;
                    }
                }
                else
                {
                    initialTouchCount = 0;
                }
            }
        }

        public override void OnBeginDrag(PointerEventData eventData)
        {
            if (SystemInfo.deviceType == DeviceType.Handheld || UnityEditor.EditorApplication.isRemoteConnected)
            {
                if (Input.touchCount >= minimumTouchCount && Input.touchCount == initialTouchCount)
                {
                    eventData.position = MultiTouchPosition;
                    base.OnBeginDrag(eventData);
                }
            }
            else if (SystemInfo.deviceType == DeviceType.Desktop)
            {
                base.OnBeginDrag(eventData);
            }
        }
        public override void OnDrag(PointerEventData eventData)
        {
            if (SystemInfo.deviceType == DeviceType.Handheld || UnityEditor.EditorApplication.isRemoteConnected)
            {
                if (Input.touchCount >= minimumTouchCount && Input.touchCount == initialTouchCount)
                {
                    eventData.position = MultiTouchPosition;
                    base.OnDrag(eventData);
                }
            }
            else if (SystemInfo.deviceType == DeviceType.Desktop)
            {
                base.OnDrag(eventData);
            }          
        }
        public override void OnEndDrag(PointerEventData eventData)
        {
            if (SystemInfo.deviceType == DeviceType.Handheld || UnityEditor.EditorApplication.isRemoteConnected)
            {
                if (Input.touchCount >= minimumTouchCount)
                {
                    eventData.position = MultiTouchPosition;
                    base.OnEndDrag(eventData);
                }
            }
            else if (SystemInfo.deviceType == DeviceType.Desktop)
            {
                base.OnEndDrag(eventData);
            }       
        }
        #endregion
    }
}

Answer 2

试试这个（尚未测试）：

public Vector2 MultiTouchPosition
{
    get
    {
        int nTouches = ((Input.touchCount <= maximumTouchCount) ? Input.touchCount : maximumTouchCount);
        if(nTouches == 1)
        {
             return Input.touches[0].position;
        } 
        else 
        {
             return Vector2.Lerp(Input.touches[0].position, Input.touches[1].position, 0.5f); //middle point between them
        }
    }
 }

由于您要处理的触摸量只能是一个或两个，因此最好以不同方式处理每个案例。

不知道你为什么要分位置，position是一个Vector2，你需要计算它们之间的中间点，可以用Vector2.Lerp来完成（0.5f决定你要中间点）