利用ExpandableListView实现侧边栏导航

ExpandableListView 是一个可以展开和收起子列表项的 Android 控件，非常适合用于实现侧边栏导航

1. 在 activity_main.xml 布局文件中添加 ExpandableListView：

    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:openDrawer="start">

   <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <!-- 主内容视图 -->
       <FrameLayout
            android:id="@+id/content_frame"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    </LinearLayout>

   <ExpandableListView
        android:id="@+id/navigation_list"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@color/white"
        android:choiceMode="singleChoice"
        android:divider="@color/gray"
        android:dividerHeight="1dp"
        android:groupIndicator="@null"/>

</androidx.drawerlayout.widget.DrawerLayout>

2. 创建一个数据模型类，例如 NavigationItem，用于存储导航项的信息：

public class NavigationItem {
    private String title;
    private int icon;

    public NavigationItem(String title, int icon) {
        this.title = title;
        this.icon = icon;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public int getIcon() {
        return icon;
    }

    public void setIcon(int icon) {
        this.icon = icon;
    }
}

3. 创建一个自定义适配器，继承自 BaseExpandableListAdapter，用于填充 ExpandableListView：

public class NavigationAdapter extends BaseExpandableListAdapter {
    private Context context;
    private List<NavigationItem> groupList;
    private Map<NavigationItem, List<NavigationItem>> childListMap;

    public NavigationAdapter(Context context, List<NavigationItem> groupList, Map<NavigationItem, List<NavigationItem>> childListMap) {
        this.context = context;
        this.groupList = groupList;
        this.childListMap = childListMap;
    }

    // ... 实现 BaseExpandableListAdapter 中的方法
}

4. 在 MainActivity 中初始化数据并设置适配器：

public class MainActivity extends AppCompatActivity {
    private DrawerLayout drawerLayout;
    private ExpandableListView navigationList;
    private NavigationAdapter navigationAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        drawerLayout = findViewById(R.id.drawer_layout);
        navigationList = findViewById(R.id.navigation_list);

        // 初始化数据
        List<NavigationItem> groupList = new ArrayList<>();
        Map<NavigationItem, List<NavigationItem>> childListMap = new HashMap<>();

        NavigationItem group1 = new NavigationItem("Group 1", R.drawable.ic_group_1);
        NavigationItem group2 = new NavigationItem("Group 2", R.drawable.ic_group_2);

        groupList.add(group1);
        groupList.add(group2);

        List<NavigationItem> childList1 = new ArrayList<>();
        childList1.add(new NavigationItem("Child 1", R.drawable.ic_child_1));
        childList1.add(new NavigationItem("Child 2", R.drawable.ic_child_2));

        List<NavigationItem> childList2 = new ArrayList<>();
        childList2.add(new NavigationItem("Child 3", R.drawable.ic_child_3));
        childList2.add(new NavigationItem("Child 4", R.drawable.ic_child_4));

        childListMap.put(group1, childList1);
        childListMap.put(group2, childList2);

        // 设置适配器
        navigationAdapter = new NavigationAdapter(this, groupList, childListMap);
        navigationList.setAdapter(navigationAdapter);

        // 设置点击事件
        navigationList.setOnChildClickListener((parent, v, groupPosition, childPosition, id) -> {
            // 处理子项点击事件
            return false;
        });

        navigationList.setOnGroupClickListener((parent, v, groupPosition, id) -> {
            // 处理分组点击事件
            return false;
        });
    }
}

现在你已经成功地使用 ExpandableListView 实现了一个侧边栏导航。你可以根据需要自定义导航项的样式和行为。