Unity 根据父对象的大小,按比例设置该对象的尺寸

ContentSizeByParent.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;


[AddComponentMenu("Layout/Content Size By Parent", 143)]
[ExecuteInEditMode]
[RequireComponent(typeof(RectTransform))]
[DisallowMultipleComponent]
public class ContentSizeByParent : UIBehaviour, ILayoutSelfController
{
    public enum AspectMode { None, WidthControlsHeight, HeightControlsWidth, FitInParent, EnvelopeParent }
    
    [SerializeField] private float m_scale = 1;
    public float scale {
        get { return m_scale; }
        set {
            if (m_scale != value)
            {
                m_scale = value;
                SetDirty();
            }
        }
    }

    [System.NonSerialized]
    private RectTransform m_Rect;

    private RectTransform rectTransform
    {
        get
        {
            if (m_Rect == null)
                m_Rect = GetComponent<RectTransform>();
            return m_Rect;
        }
    }

    private DrivenRectTransformTracker m_Tracker;

    protected ContentSizeByParent() { }

    protected override void OnEnable()
    {
        base.OnEnable();
        SetDirty();
    }

    protected override void OnDisable()
    {
        m_Tracker.Clear();
        LayoutRebuilder.MarkLayoutForRebuild(rectTransform);
        base.OnDisable();
    }

    protected override void OnRectTransformDimensionsChange()
    {
        SetDirty();
    }
    
    protected override void OnTransformParentChanged()
    {
        base.OnTransformParentChanged();
        SetDirty();
    }

    private void UpdateRect(RectTransform.Axis axis)
    {
        if (!IsActive())
            return;

        m_Tracker.Clear();

        {
            m_Tracker.Add(this, rectTransform,
                DrivenTransformProperties.Anchors |
                DrivenTransformProperties.SizeDeltaX |
                DrivenTransformProperties.SizeDeltaY);

            rectTransform.anchorMin = Vector2.zero;
            rectTransform.anchorMax = Vector2.one;

            Vector2 sizeDelta = Vector2.zero;
            Vector2 parentSize = GetParentSize();
           // if ((parentSize.y * scale < parentSize.x) ^ (m_AspectMode == AspectMode.FitInParent))
            {
                //sizeDelta.y = GetSizeDeltaToProduceSize(parentSize.x / scale, 1);
            }
            //else
            {
                //sizeDelta.x = GetSizeDeltaToProduceSize(parentSize.y * scale, 0);
            }
            sizeDelta = parentSize * scale;
            if (axis == RectTransform.Axis.Horizontal)
                rectTransform.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, sizeDelta.x);
            else
                rectTransform.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, sizeDelta.y);
        }
    }

    private float GetSizeDeltaToProduceSize(float size, int axis)
    {
        return size - GetParentSize()[axis] * (rectTransform.anchorMax[axis] - rectTransform.anchorMin[axis]);
    }

    private Vector2 GetParentSize()
    {
        RectTransform parent = rectTransform.parent as RectTransform;
        if (!parent)
            return Vector2.zero;
        return parent.rect.size;
    }

    public virtual void SetLayoutHorizontal()
    {
        UpdateRect(RectTransform.Axis.Horizontal);
    }

    public virtual void SetLayoutVertical()
    {
        UpdateRect(RectTransform.Axis.Vertical);
    }
    
    protected void SetDirty()
    {
        if (!IsActive())
            return;

        LayoutRebuilder.MarkLayoutForRebuild(rectTransform);
    }

#if UNITY_EDITOR
    protected override void OnValidate()
    {
        m_scale = Mathf.Clamp(m_scale, 0.001f, 1000f);
        SetDirty();
    }

#endif
}