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

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>

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;    }}

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}

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。