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简介

Unity中提供了三种类型的自动布局组件，分别是Grid Layou Group、Horizontal Layout Group、Vertical Layout Group，本文自定义了一个圆形的自动布局组件Circle Layout Group，如图所示：

• Radius：Circle圆的半径
• Angle Delta：两个元素之间的角度差
• Start Direction：开始布局的方向（上、下、左、右）
• Auto Refresh：是否自动刷新，开启后当子物体数量发生变化时自动刷新布局
• Control Child Size：是否控制元素的大小
• Child Size：控制元素大小

实现原理

已知圆的中心点（x0, y0），半径radius ，通过以下公式求得角度a的圆上的点坐标位置（x，y）：

float x = x0 + radius * Mathf.Cos(angle * Mathf.PI / 180f);
float y = y0 + radius * Mathf.Sin(angle * Mathf.PI / 180f);

在这里我们的子物体元素以其父级为圆心，所以不需要考虑（x0，y0）：

float x = radius * Mathf.Cos(angle * Mathf.PI / 180f);
float y = radius * Mathf.Sin(angle * Mathf.PI / 180f);

三角函数原理：
Sin正弦：y（对边） / radius（斜边）
Cos余弦：x（邻边）/ radius（斜边）

以右侧为0度起点，当方向为上方时加90度，当方向为左侧时加180度，当方向为下方时加270度，并根据角度差和元素的层级顺序计算其角度。

代码实现如下：

using UnityEngine;
using System.Collections.Generic;namespace SK.Framework.UI
{/// <summary>/// 圆形自动布局组件/// </summary>public class CircleLayoutGroup : MonoBehaviour{//半径[SerializeField] private float radius = 100f;//角度差[SerializeField] private float angleDelta = 30f;//开始的方向 0-Right 1-Up 2-Left 3-Down[SerializeField] private int startDirection = 0;//是否自动刷新布局[SerializeField] private bool autoRefresh = true;//是否控制子物体的大小[SerializeField] private bool controlChildSize = true;//子物体大小[SerializeField] private Vector2 childSize = Vector2.one * 100f;//缓存子物体数量private int cacheChildCount;private void Start(){cacheChildCount = transform.childCount;RefreshLayout();}private void Update(){//开启自动刷新if (autoRefresh){//检测到子物体数量变动if (cacheChildCount != transform.childCount){//刷新布局RefreshLayout();//再次缓存子物体数量cacheChildCount = transform.childCount;}}    }/// <summary>/// 刷新布局/// </summary>public void RefreshLayout(){//获取所有非隐藏状态的子物体List<RectTransform> children = new List<RectTransform>();for (int i = 0; i < transform.childCount; i++){Transform child = transform.GetChild(i);if (child.gameObject.activeSelf){children.Add(child as RectTransform);}}//形成的扇形的角度 = 子物体间隙数量 * 角度差float totalAngle = (children.Count - 1) * angleDelta;//总角度的一半float halfAngle = totalAngle * 0.5f;//遍历这些子物体for (int i = 0; i < children.Count; i++){RectTransform child = children[i];/* 以右侧为0度起点 * 方向为Up时角度+90 Left+180 Down+270* 方向为Right和Up时 倒序计算角度 * 确保层级中的子物体按照从左到右、从上到下的顺序自动布局 */float angle = angleDelta * (startDirection < 2 ? children.Count - 1 - i : i) - halfAngle + startDirection * 90f;//计算x、y坐标float x = radius * Mathf.Cos(angle * Mathf.PI / 180f);float y = radius * Mathf.Sin(angle * Mathf.PI / 180f);//为子物体赋值坐标Vector2 anchorPos = child.anchoredPosition;anchorPos.x = x;anchorPos.y = y;child.anchoredPosition = anchorPos;//控制子物体大小if (controlChildSize){child.SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, childSize.x);child.SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, childSize.y);}}}}
}

Editor 编辑器

通过上述代码可以实现Runtime运行时的布局自动刷新，想要在Editor编辑环境编辑时自动刷新还需要自定义Editor编辑器，代码如下：

#if UNITY_EDITOR[CustomEditor(typeof(CircleLayoutGroup))]public class CircleLayoutGroupEditor : Editor{private enum Direction{Right = 0,Up = 1,Left = 2,Down = 3}private CircleLayoutGroup circleLayoutGroup;private SerializedProperty radius;private SerializedProperty angleDelta;private SerializedProperty startDirection;private SerializedProperty autoRefresh;private SerializedProperty controlChildSize;private SerializedProperty childSize;private Direction direction;private void OnEnable(){circleLayoutGroup = target as CircleLayoutGroup;radius = serializedObject.FindProperty("radius");angleDelta = serializedObject.FindProperty("angleDelta");startDirection = serializedObject.FindProperty("startDirection");autoRefresh = serializedObject.FindProperty("autoRefresh");controlChildSize = serializedObject.FindProperty("controlChildSize");childSize = serializedObject.FindProperty("childSize");direction = (Direction)startDirection.intValue;circleLayoutGroup.RefreshLayout();}public override void OnInspectorGUI(){float newRadius = EditorGUILayout.FloatField("Radius", radius.floatValue);if (newRadius != radius.floatValue){Undo.RecordObject(target, "Radius");radius.floatValue = newRadius;IsChanged();}float newAngleDelta = EditorGUILayout.FloatField("Angle Delta", angleDelta.floatValue);if (newAngleDelta != angleDelta.floatValue){Undo.RecordObject(target, "Angle Delta");angleDelta.floatValue = newAngleDelta;IsChanged();}Direction newDirection = (Direction)EditorGUILayout.EnumPopup("Start Direction", direction);if (newDirection != direction) {Undo.RecordObject(target, "Start Direction");direction = newDirection;startDirection.intValue = (int)direction;IsChanged();}bool newAutoRefresh = EditorGUILayout.Toggle("Auto Refresh", autoRefresh.boolValue);if (newAutoRefresh != autoRefresh.boolValue){Undo.RecordObject(target, "Angle Refresh");autoRefresh.boolValue = newAutoRefresh;IsChanged();}bool newControlChildSize = EditorGUILayout.Toggle("Control Child Size", controlChildSize.boolValue);if (newControlChildSize != controlChildSize.boolValue){Undo.RecordObject(target, "Control Child Size");controlChildSize.boolValue = newControlChildSize;IsChanged();}if (controlChildSize.boolValue){Vector2 newChildSize = EditorGUILayout.Vector2Field("Child Size", childSize.vector2Value);if (newChildSize != childSize.vector2Value){Undo.RecordObject(target, "Child Size");childSize.vector2Value = newChildSize;IsChanged();}}}private void IsChanged(){if (GUI.changed){serializedObject.ApplyModifiedProperties();EditorUtility.SetDirty(target);circleLayoutGroup.RefreshLayout();}}}
#endif

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