Android ExpandableListView 兩層列表完整實作教學

標題雖提及「JavaMail QQ 郵件設定」，但實際內容為 Android ExpandableListView 雙層可展開列表 的完整範例。本文整理關鍵實作步驟與程式碼架構，供快速參考。

版面配置 (XML)

<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#FFFFFF">

    <ExpandableListView
        android:id="@+id/elv_journal_catalog"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:cacheColorHint="#FFFFFF" />
</LinearLayout>

Activity 初始化與資料載入

public class CatalogActivity extends Activity {
    private ExpandableListView elv;
    private List<List<Article>> childrenData;
    private JournalCatalogListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.journal_catalog);
        initView();
        loadData();
    }

    private void initView() {
        elv = findViewById(R.id.elv_journal_catalog);
        elv.setGroupIndicator(null);      // 隱藏預設展開圖示
        elv.setDivider(null);             // 移除分隔線
        elv.setOnChildClickListener(listener);
    }

    private void loadData() {
        // 非同步載入資料（略），完成後：
        adapter = new JournalCatalogListAdapter(this, childrenData);
        elv.setAdapter(adapter);
        // 若需預設展開某群組：
        // elv.expandGroup(groupPosition);
    }
}

自訂 BaseExpandableListAdapter

關鍵方法說明：

• getGroupCount() / getChildrenCount(groupPosition)：回傳群組數與子項數。
• getGroupView() / getChildView()：分別渲染群組列與子項列，建議使用 ViewHolder 模式複用 convertView。
• hasStableIds() 回傳 true 可提升效能。

public class JournalCatalogListAdapter extends BaseExpandableListAdapter {
    private final LayoutInflater inflater;
    private final String[] groupTitles = {"美顏美體", "潮流單品", "娛樂八卦", "情感", "觀點", "健康生活"};
    private final List<List<Article>> children;

    public JournalCatalogListAdapter(Context context, List<List<Article>> children) {
        this.children = children;
        this.inflater = LayoutInflater.from(context);
    }

    @Override public int getGroupCount() { return groupTitles.length; }
    @Override public int getChildrenCount(int groupPosition) { return children.get(groupPosition).size(); }
    @Override public Object getGroup(int groupPosition) { return groupTitles[groupPosition]; }
    @Override public Object getChild(int groupPosition, int childPosition) { return children.get(groupPosition).get(childPosition); }
    @Override public long getGroupId(int groupPosition) { return groupPosition; }
    @Override public long getChildId(int groupPosition, int childPosition) { return childPosition; }
    @Override public boolean hasStableIds() { return true; }
    @Override public boolean isChildSelectable(int groupPosition, int childPosition) { return true; }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
        GroupHolder holder;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.journal_catalog_list_item_title, parent, false);
            holder = new GroupHolder(convertView);
            convertView.setTag(holder);
        } else {
            holder = (GroupHolder) convertView.getTag();
        }
        holder.title.setText(getGroup(groupPosition).toString());
        return convertView;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        ChildHolder holder;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.journal_catalog_list_item_content, parent, false);
            holder = new ChildHolder(convertView);
            convertView.setTag(holder);
        } else {
            holder = (ChildHolder) convertView.getTag();
        }
        Article article = (Article) getChild(groupPosition, childPosition);
        holder.title.setText(article.getTitle());
        return convertView;
    }

    static class GroupHolder { TextView title; GroupHolder(View v) { title = v.findViewById(R.id.tv_journal_catalog_list_item_title); } }
    static class ChildHolder { TextView title; ChildHolder(View v) { title = v.findViewById(R.id.tv_journal_catalog_list_item_content); } }
}

常見客製化需求

• 隱藏/替換群組展開圖示：setGroupIndicator(null) 或 setGroupIndicator(Drawable)。
• 預設展開特定群組：expandGroup(position)。
• 動態資料更新：修改 childrenData 後呼叫 adapter.notifyDataSetChanged()。