Unity/TMPro/Dropdown

TMP_Dropdownのスクリプトで制御

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using TMPro;
public class SettingScene : MonoBehaviour
{
    TMP_Dropdown areaDropdown;
    List<string> areas;
    string area;
    void Start()
    {
        AreaDropdownInit();
        areaDropdown = this.transform.Find("AreaDropdown").GetComponent<TMP_Dropdown>();
        areaDropdown.onValueChanged.AddListener(delegate {
            AreaDropdownValueChanged(areaDropdown);
        });
    }
    void AreaDropdownInit()
    {
        areas = new List<string>();
        areas.Add("simple");
        areas.Add("sabaku");
        areas.Add("sushi");
        List<TMP_Dropdown.OptionData> optionMessages = new List<TMP_Dropdown.OptionData>();
        TMP_Dropdown areaDropdown = this.transform.Find("AreaDropdown").GetComponent<TMP_Dropdown>();
        areaDropdown.ClearOptions();
        foreach (string area in areas)
        {
            TMP_Dropdown.OptionData optionData;
            optionData = new TMP_Dropdown.OptionData();
            optionData.text = area;
            optionMessages.Add(optionData);
        }
        foreach (TMP_Dropdown.OptionData message in optionMessages)
        {
            areaDropdown.options.Add(message);
        }
        areaDropdown.value = areas.IndexOf(area);
        this.transform.Find("AreaDropdown/Label").GetComponent<TextMeshProUGUI>().text = areas[areaDropdown.value].ToString();
    }
    void AreaDropdownValueChanged(TMP_Dropdown change)
    {
        area = areas[change.value];
        this.transform.Find("AreaDropdown/Label").GetComponent<TextMeshProUGUI>().text = areas[areaDropdown.value].ToString();
    }
}

Dropdownを開いたときに選択した項目を表示する方法

UIのButtonをDropdownに被せて、ButtonをクリックしたときにDropdownを開く以下処理を走らせる。

選択Indexが表示領域の中央より上なら、スクロールしないように。

UniTaskバージョン

using Cysharp.Threading.Tasks;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

public class TMPDropdownScrollFix : MonoBehaviour
{
    [SerializeField]
    public TMP_Dropdown dropdown;
    [SerializeField]
    private Button button;
    void Start()
    {
        button.onClick.AddListener(() => OpenDropdownAsync().Forget());
    }
    public async UniTaskVoid OpenDropdownAsync()
    {
        dropdown.Show();
        await ScrollToSelectedAsync();
    }

    async UniTask ScrollToSelectedAsync()
    {
        // UI生成待ち（超重要）
        await UniTask.NextFrame();
        await UniTask.NextFrame();

        var scrollRect = dropdown.GetComponentInChildren<ScrollRect>();
        if (scrollRect == null) return;

        int index = dropdown.value;
        int totalCount = dropdown.options.Count;
        if (totalCount <= 1) return;

        // ===== 表示行数を計算 =====
        var viewport = scrollRect.viewport.rect.height;
        var content = scrollRect.content;

        if (content.childCount == 0) return;

        float itemHeight = ((RectTransform)content.GetChild(0)).rect.height;
        int visibleCount = Mathf.FloorToInt(viewport / itemHeight);

        int centerIndex = visibleCount / 2;

        // ===== 中央まではスクロールしない =====
        if (index <= centerIndex)
        {
            scrollRect.verticalNormalizedPosition = 1f;
            return;
        }

        // ===== 中央を超えたらスクロール =====
        float scrollIndex = index - centerIndex;
        float maxScrollIndex = totalCount - visibleCount;

        if (maxScrollIndex <= 0)
        {
            scrollRect.verticalNormalizedPosition = 1f;
            return;
        }

        float normalizedPos = 1f - (scrollIndex / maxScrollIndex);
        scrollRect.verticalNormalizedPosition = Mathf.Clamp01(normalizedPos);
    }
}

コルーチンパターン

using System.Collections;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

public class TMPDropdownScrollFix : MonoBehaviour
{
    [SerializeField]
    public TMP_Dropdown dropdown;
    [SerializeField]
    private Button button;
    void Start()
    {
        button.onClick.AddListener(() => OpenDropdown());
    }
    void OpenDropdown()
    {
        dropdown.Show();
        StartCoroutine(ScrollToSelected());
    }

    IEnumerator ScrollToSelected()
    {
        // UI生成待ち（超重要）
        yield return null;
        yield return null;

        var scrollRect = dropdown.GetComponentInChildren<ScrollRect>();
        if (scrollRect == null) yield break;

        var content = scrollRect.content;
        if (content.childCount == 0) yield break;

        int index = dropdown.value;
        int totalCount = dropdown.options.Count;
        if (totalCount <= 1) yield break;

        // ===== 表示行数を計算 =====
        float viewportHeight = scrollRect.viewport.rect.height;
        float itemHeight =
            ((RectTransform)content.GetChild(0)).rect.height;

        int visibleCount = Mathf.FloorToInt(viewportHeight / itemHeight);
        int centerIndex = visibleCount / 2;

        // ===== 中央まではスクロールしない =====
        if (index <= centerIndex)
        {
            scrollRect.verticalNormalizedPosition = 1f;
            yield break;
        }

        // ===== 中央を超えたらスクロール =====
        float maxScrollIndex = totalCount - visibleCount;
        if (maxScrollIndex <= 0)
        {
            scrollRect.verticalNormalizedPosition = 1f;
            yield break;
        }

        float scrollIndex = index - centerIndex;
        float normalizedPos = 1f - (scrollIndex / maxScrollIndex);

        scrollRect.verticalNormalizedPosition = Mathf.Clamp01(normalizedPos);
    }
}