UICenterOnChild.cs

using System.Collections.Generic;
using UnityEngine;

[AddComponentMenu("NGUI/Interaction/Center Scroll View on Child")]
public class UICenterOnChild : MonoBehaviour
{
	public delegate void OnCenterCallback(GameObject centeredObject);

	public float springStrength = 8f;

	public float nextPageThreshold;

	public SpringPanel.OnFinished onFinished;

	public OnCenterCallback onCenter;

	private UIScrollView mScrollView;

	private GameObject mCenteredObject;

	public GameObject centeredObject => mCenteredObject;

	private void Start()
	{
		Recenter();
	}

	private void OnEnable()
	{
		if ((bool)mScrollView)
		{
			mScrollView.centerOnChild = this;
			Recenter();
		}
	}

	private void OnDisable()
	{
		if ((bool)mScrollView)
		{
			mScrollView.centerOnChild = null;
		}
	}

	private void OnDragFinished()
	{
		if (base.enabled)
		{
			Recenter();
		}
	}

	private void OnValidate()
	{
		nextPageThreshold = Mathf.Abs(nextPageThreshold);
	}

	[ContextMenu("Execute")]
	public void Recenter()
	{
		if (mScrollView == null)
		{
			mScrollView = NGUITools.FindInParents<UIScrollView>(base.gameObject);
			if (mScrollView == null)
			{
				Debug.LogWarning(GetType() + " requires " + typeof(UIScrollView) + " on a parent object in order to work", this);
				base.enabled = false;
				return;
			}
			if ((bool)mScrollView)
			{
				mScrollView.centerOnChild = this;
				mScrollView.onDragFinished = OnDragFinished;
			}
			if (mScrollView.horizontalScrollBar != null)
			{
				mScrollView.horizontalScrollBar.onDragFinished = OnDragFinished;
			}
			if (mScrollView.verticalScrollBar != null)
			{
				mScrollView.verticalScrollBar.onDragFinished = OnDragFinished;
			}
		}
		if (!(mScrollView.panel == null))
		{
			Transform transform = base.transform;
			if (transform.childCount != 0)
			{
				Vector3[] worldCorners = mScrollView.panel.worldCorners;
				Vector3 vector = (worldCorners[2] + worldCorners[0]) * 0.5f;
				Vector3 velocity = mScrollView.currentMomentum * mScrollView.momentumAmount;
				Vector3 a = NGUIMath.SpringDampen(ref velocity, 9f, 2f);
				Vector3 b = vector - a * 0.01f;
				float num = 3.40282347E+38f;
				Transform target = null;
				int num2 = 0;
				int i = 0;
				for (int childCount = transform.childCount; i < childCount; i++)
				{
					Transform child = transform.GetChild(i);
					if (child.gameObject.activeInHierarchy)
					{
						float num3 = Vector3.SqrMagnitude(child.position - b);
						if (num3 < num)
						{
							num = num3;
							target = child;
							num2 = i;
						}
					}
				}
				if (nextPageThreshold > 0f && UICamera.currentTouch != null && mCenteredObject != null && mCenteredObject.transform == transform.GetChild(num2))
				{
					Vector2 totalDelta = UICamera.currentTouch.totalDelta;
					float num4 = 0f;
					switch (mScrollView.movement)
					{
					case UIScrollView.Movement.Horizontal:
						num4 = totalDelta.x;
						break;
					case UIScrollView.Movement.Vertical:
						num4 = totalDelta.y;
						break;
					default:
						num4 = totalDelta.magnitude;
						break;
					}
					if (Mathf.Abs(num4) > nextPageThreshold)
					{
						UIGrid component = GetComponent<UIGrid>();
						if (component != null && component.sorting != 0)
						{
							List<Transform> childList = component.GetChildList();
							if (num4 > nextPageThreshold)
							{
								target = ((num2 <= 0) ? childList[0] : childList[num2 - 1]);
							}
							else if (num4 < 0f - nextPageThreshold)
							{
								target = ((num2 >= childList.Count - 1) ? childList[childList.Count - 1] : childList[num2 + 1]);
							}
						}
						else
						{
							Debug.LogWarning("Next Page Threshold requires a sorted UIGrid in order to work properly", this);
						}
					}
				}
				CenterOn(target, vector);
			}
		}
	}

	private void CenterOn(Transform target, Vector3 panelCenter)
	{
		if (target != null && mScrollView != null && mScrollView.panel != null)
		{
			Transform cachedTransform = mScrollView.panel.cachedTransform;
			mCenteredObject = target.gameObject;
			Vector3 a = cachedTransform.InverseTransformPoint(target.position);
			Vector3 b = cachedTransform.InverseTransformPoint(panelCenter);
			Vector3 b2 = a - b;
			if (!mScrollView.canMoveHorizontally)
			{
				b2.x = 0f;
			}
			if (!mScrollView.canMoveVertically)
			{
				b2.y = 0f;
			}
			b2.z = 0f;
			SpringPanel.Begin(mScrollView.panel.cachedGameObject, cachedTransform.localPosition - b2, springStrength).onFinished = onFinished;
		}
		else
		{
			mCenteredObject = null;
		}
		if (onCenter != null)
		{
			onCenter(mCenteredObject);
		}
	}

	public void CenterOn(Transform target)
	{
		if (mScrollView != null && mScrollView.panel != null)
		{
			Vector3[] worldCorners = mScrollView.panel.worldCorners;
			Vector3 panelCenter = (worldCorners[2] + worldCorners[0]) * 0.5f;
			CenterOn(target, panelCenter);
		}
	}
}