【Unity】Animatorのステートを自動取得してモーションを確認できるUIパネル（Editor only）

MecanimCheckPanel.cs

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
#if UNITY_EDITOR
using UnityEditor.Animations;
#endif

/// <summary>
/// Mecanimモーション確認用のUIパネル
/// </summary>
public class MecanimCheckPanel : MonoBehaviour
{
    /// <summary>
    /// ターゲットのアニメーター
    /// </summary>
    [SerializeField]
    private Animator _animator = null;

    /// <summary>
    /// レイヤー切り替えドロップダウン
    /// </summary>
    [SerializeField]
    private Dropdown _layerDropdown = null;

    /// <summary>
    /// ステート切り替えドロップダウン
    /// </summary>
    [SerializeField]
    private Dropdown _stateDropdown = null;

    /// <summary>
    /// モーション移行時間
    /// </summary>
    [SerializeField]
    private float _crossFadeDuration = 0.2f;

    private Dictionary<string, List<string>> _layerStatesTable = new Dictionary<string, List<string>>();

    private void Awake()
    {
#if UNITY_EDITOR
        // AnimatorControllerのデータ収集
        var layerNameList = new List<string>();
        var controller = _animator.runtimeAnimatorController as AnimatorController;
        foreach (var layer in controller.layers)
        {
            layerNameList.Add(layer.name);

            var stateNameList = new List<string>();
            foreach (var child in layer.stateMachine.states)
            {
                stateNameList.Add(child.state.name);
            }

            _layerStatesTable.Add(layer.name, stateNameList);
        }

        // Dropdownの設定
        _layerDropdown.ClearOptions();
        _stateDropdown.ClearOptions();

        _layerDropdown.AddOptions(layerNameList);

        _layerDropdown.onValueChanged.AddListener(x => RefreshStateDropdown(_layerDropdown.options[x].text));
        _stateDropdown.onValueChanged.AddListener(x =>
        {
            ChangeMotion(_layerDropdown.options[_layerDropdown.value].text, _stateDropdown.options[x].text);
        });
#else
        // Editor only
        Destroy(gameObject);
#endif
    }

    private void Start()
    {
        _layerDropdown.onValueChanged.Invoke(0);
    }

    /// <summary>
    /// ステートのドロップダウンを更新
    /// </summary>
    /// <param name="layer">レイヤー名</param>
    private void RefreshStateDropdown(string layer)
    {
        _stateDropdown.ClearOptions();
        _stateDropdown.AddOptions(_layerStatesTable[layer]);

        _stateDropdown.onValueChanged.Invoke(0);
    }

    /// <summary>
    /// モーションを変更する
    /// </summary>
    /// <param name="layerName">レイヤー名</param>
    /// <param name="stateName">目標ステート名</param>
    private void ChangeMotion(string layerName, string stateName)
    {
        var layer = _animator.GetLayerIndex(layerName);
        _animator.CrossFadeInFixedTime(stateName, _crossFadeDuration, layer);
    }
}

Qiita: https://qiita.com/neusstudio/items/64fef4a9dd6d6a620681