如何使用 Unity UI 滚动到 ScrollRect 中的特定元素？

Question

我使用 Unity 5.1 为手机游戏制作了一个注册表单。为此，我使用 Unity UI 组件：ScrollRect + Autolayout（垂直布局）+ 文本（标签）+ 输入字段。这部分工作正常。

但是，当键盘打开时，所选字段位于键盘下方。有没有办法以编程方式滚动表单以使所选字段进入视图？

我已经尝试使用 ScrollRect.verticalNormalizedPosition 并且它可以很好地滚动一些，但是我无法让选定的字段出现在我想要的地方。

感谢您的帮助！

Answer 1

我将给您一段我的代码片段，因为我想对您有所帮助。希望这对您有所帮助！

protected ScrollRect scrollRect;
protected RectTransform contentPanel;

public void SnapTo(RectTransform target)
{
    Canvas.ForceUpdateCanvases();

    contentPanel.anchoredPosition =
            (Vector2)scrollRect.transform.InverseTransformPoint(contentPanel.position)
            - (Vector2)scrollRect.transform.InverseTransformPoint(target.position);
}

Answer 2

是的，这可以使用编码垂直滚动，请试试这个代码：

//Set Scrollbar Value - For Displaying last message of content
Canvas.ForceUpdateCanvases ();
verticleScrollbar.value = 0f;
Canvas.ForceUpdateCanvases ();

当我开发聊天功能时，这段代码对我来说工作正常。

Answer 3

这是我将选定对象固定到 ScrollRect 中的方法

private ScrollRect scrollRect;
private RectTransform contentPanel;

public void ScrollReposition(RectTransform obj)
{
    var objPosition = (Vector2)scrollRect.transform.InverseTransformPoint(obj.position);
    var scrollHeight = scrollRect.GetComponent<RectTransform>().rect.height;
    var objHeight = obj.rect.height;

    if (objPosition.y > scrollHeight / 2)
    {
        contentPanel.localPosition = new Vector2(contentPanel.localPosition.x,
            contentPanel.localPosition.y - objHeight - Padding.top);
    }

    if (objPosition.y < -scrollHeight / 2)
    {
        contentPanel.localPosition = new Vector2(contentPanel.localPosition.x,
contentPanel.localPosition.y + objHeight + Padding.bottom);
    }
}

Answer 4

None 的建议对我有用，以下代码对我有用

这是扩展名

using UnityEngine;
using UnityEngine.UI;

namespace BlinkTalk
{
    public static class ScrollRectExtensions
    {
        public static Vector2 GetSnapToPositionToBringChildIntoView(this ScrollRect instance, RectTransform child)
        {
            Canvas.ForceUpdateCanvases();
            Vector2 viewportLocalPosition = instance.viewport.localPosition;
            Vector2 childLocalPosition   = child.localPosition;
            Vector2 result = new Vector2(
                0 - (viewportLocalPosition.x + childLocalPosition.x),
                0 - (viewportLocalPosition.y + childLocalPosition.y)
            );
            return result;
        }
    }
}

下面是我如何使用它将内容的直接子项滚动到视图中

    private void Update()
    {
        MyScrollRect.content.localPosition = MyScrollRect.GetSnapToPositionToBringChildIntoView(someChild);
    }

Answer 5

width表示scroll rect中childern的宽度（假设所有childern的宽度都相同），spacing表示childern之间space，index表示要到达的目标元素

public float getSpecificItem (float pWidth, float pSpacing,int pIndex) {
    return (pIndex * pWidth) - pWidth + ((pIndex - 1) * pSpacing);
}

Answer 6

虽然@maksymiuk 的回答是最正确的，因为它适当地考虑了锚点、枢轴和所有其他感谢 InverseTransformPoint() 函数，但它对我来说仍然不是开箱即用的——因为垂直滚动条，它也在改变它的 X 位置。所以我只是进行了更改以检查是否启用了垂直或水平滚动，如果未启用则不更改它们的轴。

public static void SnapTo( this ScrollRect scroller, RectTransform child )
{
    Canvas.ForceUpdateCanvases();

    var contentPos = (Vector2)scroller.transform.InverseTransformPoint( scroller.content.position );
    var childPos = (Vector2)scroller.transform.InverseTransformPoint( child.position );
    var endPos = contentPos - childPos;
    // If no horizontal scroll, then don't change contentPos.x
    if( !scroller.horizontal ) endPos.x = contentPos.x;
    // If no vertical scroll, then don't change contentPos.y
    if( !scroller.vertical ) endPos.y = contentPos.y;
    scroller.content.anchoredPosition = endPos;
}

Answer 7

垂直调整：

[SerializeField]
private ScrollRect _scrollRect;

private void ScrollToCurrentElement()
{
    var siblingIndex = _currentListItem.transform.GetSiblingIndex();

    float pos = 1f - (float)siblingIndex / _scrollRect.content.transform.childCount;

    if (pos < 0.4)
    {
        float correction = 1f / _scrollRect.content.transform.childCount;
        pos -= correction;
    }

    _scrollRect.verticalNormalizedPosition = pos;
}

Answer 8

我这个问题版本的前提条件：

我要滚动到的 element 应该完全可见（最小间隙）
element 是 scrollRect 内容的直接子项
如果 element 已经完全可见，则保持 scoll 位置
我只关心垂直维度

这是最适合我的方法（感谢其他灵感）：

// ScrollRect scrollRect;
// RectTransform element;
// Fully show `element` inside `scrollRect` with at least 25px clearance
scrollArea.EnsureVisibility(element, 25);

使用此扩展方法：

public static void EnsureVisibility(this ScrollRect scrollRect, RectTransform child, float padding=0)
{
    Debug.Assert(child.parent == scrollRect.content,
        "EnsureVisibility assumes that 'child' is directly nested in the content of 'scrollRect'");

    float viewportHeight = scrollRect.viewport.rect.height;
    Vector2 scrollPosition = scrollRect.content.anchoredPosition;

    float elementTop = child.anchoredPosition.y;
    float elementBottom = elementTop - child.rect.height;

    float visibleContentTop = -scrollPosition.y - padding;
    float visibleContentBottom = -scrollPosition.y - viewportHeight + padding;

    float scrollDelta =
        elementTop > visibleContentTop ? visibleContentTop - elementTop :
        elementBottom < visibleContentBottom ? visibleContentBottom - elementBottom :
        0f;

    scrollPosition.y += scrollDelta;
    scrollRect.content.anchoredPosition = scrollPosition;
}

Answer 9

Peter Morris 对具有移动类型 "elastic" 的 ScrollRects 的回答的变体。令我困扰的是，滚动矩形一直为边缘情况（第一个或最后几个元素）设置动画。希望有用:

/// <summary>
/// Thanks to 
/// </summary>
/// <param name="instance"></param>
/// <param name="child"></param>
/// <returns></returns>
public static IEnumerator BringChildIntoView(this UnityEngine.UI.ScrollRect instance, RectTransform child)
{
    Canvas.ForceUpdateCanvases();
    Vector2 viewportLocalPosition = instance.viewport.localPosition;
    Vector2 childLocalPosition = child.localPosition;
    Vector2 result = new Vector2(
        0 - (viewportLocalPosition.x + childLocalPosition.x),
        0 - (viewportLocalPosition.y + childLocalPosition.y)
    );
    instance.content.localPosition = result;

    yield return new WaitForUpdate();

    instance.horizontalNormalizedPosition = Mathf.Clamp(instance.horizontalNormalizedPosition, 0f, 1f);
    instance.verticalNormalizedPosition = Mathf.Clamp(instance.verticalNormalizedPosition, 0f, 1f);
}

虽然它引入了一帧延迟。

更新：这是一个不引入帧延迟的版本，它还考虑了内容的缩放：

/// <summary>
/// Based on 
/// </summary>
/// <param name="instance"></param>
/// <param name="child"></param>
/// <returns></returns>
public static void BringChildIntoView(this UnityEngine.UI.ScrollRect instance, RectTransform child)
{
    instance.content.ForceUpdateRectTransforms();
    instance.viewport.ForceUpdateRectTransforms();

    // now takes scaling into account
    Vector2 viewportLocalPosition = instance.viewport.localPosition;
    Vector2 childLocalPosition = child.localPosition;
    Vector2 newContentPosition = new Vector2(
        0 - ((viewportLocalPosition.x * instance.viewport.localScale.x) + (childLocalPosition.x * instance.content.localScale.x)),
        0 - ((viewportLocalPosition.y * instance.viewport.localScale.y) + (childLocalPosition.y * instance.content.localScale.y))
    );

    // clamp positions
    instance.content.localPosition = newContentPosition;
    Rect contentRectInViewport = TransformRectFromTo(instance.content.transform, instance.viewport);
    float deltaXMin = contentRectInViewport.xMin - instance.viewport.rect.xMin;
    if(deltaXMin > 0) // clamp to <= 0
    {
        newContentPosition.x -= deltaXMin;
    }
    float deltaXMax = contentRectInViewport.xMax - instance.viewport.rect.xMax;
    if (deltaXMax < 0) // clamp to >= 0
    {
        newContentPosition.x -= deltaXMax;
    }
    float deltaYMin = contentRectInViewport.yMin - instance.viewport.rect.yMin;
    if (deltaYMin > 0) // clamp to <= 0
    {
        newContentPosition.y -= deltaYMin;
    }
    float deltaYMax = contentRectInViewport.yMax - instance.viewport.rect.yMax;
    if (deltaYMax < 0) // clamp to >= 0
    {
        newContentPosition.y -= deltaYMax;
    }

    // apply final position
    instance.content.localPosition = newContentPosition;
    instance.content.ForceUpdateRectTransforms();
}

/// <summary>
/// Converts a Rect from one RectTransfrom to another RectTransfrom.
/// Hint: use the root Canvas Transform as "to" to get the reference pixel positions.
/// </summary>
/// <param name="from"></param>
/// <param name="to"></param>
/// <returns></returns>
public static Rect TransformRectFromTo(Transform from, Transform to)
{
    RectTransform fromRectTrans = from.GetComponent<RectTransform>();
    RectTransform toRectTrans = to.GetComponent<RectTransform>();

    if (fromRectTrans != null && toRectTrans != null)
    {
        Vector3[] fromWorldCorners = new Vector3[4];
        Vector3[] toLocalCorners = new Vector3[4];
        Matrix4x4 toLocal = to.worldToLocalMatrix;
        fromRectTrans.GetWorldCorners(fromWorldCorners);
        for (int i = 0; i < 4; i++)
        {
            toLocalCorners[i] = toLocal.MultiplyPoint3x4(fromWorldCorners[i]);
        }

        return new Rect(toLocalCorners[0].x, toLocalCorners[0].y, toLocalCorners[2].x - toLocalCorners[1].x, toLocalCorners[1].y - toLocalCorners[0].y);
    }

    return default(Rect);
}

Answer 10

如果有人正在寻找平滑的滚动（使用 lerp）。

[SerializeField]
private ScrollRect _scrollRectComponent; //your scroll rect component
[SerializeField]
RectTransform _container; //content transform of the scrollrect
private IEnumerator LerpToChild(RectTransform target)
{
    Vector2 _lerpTo = (Vector2)_scrollRectComponent.transform.InverseTransformPoint(_container.position) - (Vector2)_scrollRectComponent.transform.InverseTransformPoint(target.position);
    bool _lerp = true;
    Canvas.ForceUpdateCanvases();

    while(_lerp)
    {
        float decelerate = Mathf.Min(10f * Time.deltaTime, 1f);
        _container.anchoredPosition = Vector2.Lerp(_scrollRectComponent.transform.InverseTransformPoint(_container.position), _lerpTo, decelerate);
        if (Vector2.SqrMagnitude((Vector2)_scrollRectComponent.transform.InverseTransformPoint(_container.position) - _lerpTo) < 0.25f)
        {
            _container.anchoredPosition = _lerpTo;
            _lerp = false;
        }
        yield return null;
    }
}

Answer 11

这是我为解决这个问题而创建的。将此行为放在可通过控制器 UI 导航选择的每个按钮上。它支持完全嵌套的子对象。它仅支持垂直 scrollrects，但可以轻松适应水平滚动。

    using UnityEngine;
    using System;
    using UnityEngine.EventSystems;
    using UnityEngine.UI;
    
    namespace Legend
    {
        public class ScrollToOnSelect: MonoBehaviour, ISelectHandler
        {
            ScrollRect scrollRect;
            RectTransform target;
    
            void Start()
            {
                scrollRect = GetComponentInParent<ScrollRect>();
                target = (RectTransform)this.transform;
            }
    
            Vector3 LocalPositionWithinAncestor(Transform ancestor, Transform target)
            {
                var result = Vector3.zero;
                while (ancestor != target && target != null)
                {
                    result += target.localPosition;
                    target = target.parent;
                }
                return result;
            }
    
            public void EnsureScrollVisible()
            {
                Canvas.ForceUpdateCanvases();
    
                var targetPosition = LocalPositionWithinAncestor(scrollRect.content, target);
                var top = (-targetPosition.y) - target.rect.height / 2;
                var bottom = (-targetPosition.y) + target.rect.height / 2;
    
                var topMargin = 100; // this is here because there are headers over the buttons sometimes
    
                var result = scrollRect.content.anchoredPosition;
                if (result.y > top - topMargin)
                    result.y = top - topMargin;
                if (result.y + scrollRect.viewport.rect.height < bottom)
                    result.y = bottom - scrollRect.viewport.rect.height;
    
                //Debug.Log($"{targetPosition} {target.rect.size} {top} {bottom} {scrollRect.content.anchoredPosition}->{result}");
    
                scrollRect.content.anchoredPosition = result;
            }
    
            public void OnSelect(BaseEventData eventData)
            {
                if (scrollRect != null)
                    EnsureScrollVisible();
            }
        }
    }

Answer 12

简单而完美

            var pos = 1 - ((content.rect.height / 2 - target.localPosition.y) / content.rect.height);
            scrollRect.normalizedPosition = new Vector2(0, pos);

如何使用 Unity UI 滚动到 ScrollRect 中的特定元素？

How to scroll to a specific element in ScrollRect with Unity UI?

user-interface

unity3d

unity3d-gui