[Unity] Custom PropertyDrawer for a class with an array

当一个阵列B的长度是等于另一个变数A里的值。不做额外处理的话，必须随时注意A与B是否相同。为了方便及稳定性，不彷自订一个class包含变数变数A与阵列B，并为此class订做一个PropertyDrawer，如此一来，既自动又正确。先附上图说明before与After。

範例目标 (MeshRenderer上的Materials有几个，阵列长度就是多少)

Before (指定完MeshRenderer后，还需要指定阵列长度)

After (指定完MeshRenderer后，自动根据Materials初始化阵列)

範例程式码 (Sample.cs)

using System;using UnityEngine;public enum State { _1, _2, _3 }// Custom serializable class[Serializable]public class Table{    public MeshRenderer meshRenderer;    public State[] states;}public class Sample : MonoBehaviour{    public Table table;}

範例程式码 (TableDrawer.cs)

using UnityEditor;using UnityEngine;[CustomPropertyDrawer(typeof(Table))]public class TableDrawer : PropertyDrawer{    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)    {        EditorGUI.BeginProperty(position, label, property);        Rect rLabel = position;        Rect rField = EditorGUI.PrefixLabel(position, GUIUtility.GetControlID(FocusType.Passive), label);        rField.height = EditorGUIUtility.singleLineHeight;        SerializedProperty spMesh = property.FindPropertyRelative("mesh");        SerializedProperty spStates = property.FindPropertyRelative("states");        EditorGUI.PropertyField(rField, spMesh, GUIContent.none);        rField.y += EditorGUIUtility.singleLineHeight;        MeshRenderer mesh = spMesh.objectReferenceValue as MeshRenderer;        if (mesh != null && mesh.sharedMaterials.Length > 0)        {            spStates.arraySize = mesh.sharedMaterials.Length;            for (int i = 0; i < spStates.arraySize; ++i)            {                SerializedProperty spLipShape = spStates.GetArrayElementAtIndex(i);                string labelName = "  " + mesh.sharedMaterials[i].name;                Rect rt = new Rect(rLabel.x, rField.y, rLabel.width - rField.width, rLabel.height);                EditorGUI.LabelField(rt, labelName);                EditorGUI.PropertyField(rField, spLipShape, GUIContent.none);                rField.y += EditorGUIUtility.singleLineHeight;            }        }        EditorGUI.EndProperty();    }    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)    {        int lineCount = 1;        SerializedProperty spMesh = property.FindPropertyRelative("mesh");        MeshRenderer mesh = spMesh.objectReferenceValue as MeshRenderer;        if (mesh != null) lineCount += mesh.sharedMaterials.Length;        return EditorGUIUtility.singleLineHeight * lineCount;    }}