android实现底部导航栏

Android实现底部导航栏的方式有很多种，其中比较常用的方式是使用BottomNavigationView和Fragment组合实现。具体实现步骤如下：

1.在布局文件中添加BottomNavigationView组件，设置菜单项和样式。

2.在Activity中获取BottomNavigationView组件，并设置OnNavigationItemSelectedListener监听器，处理菜单项的点击事件。

3.创建多个Fragment用于显示不同的页面内容。

4.在Activity中使用FragmentManager和FragmentTransaction管理Fragment的切换，根据菜单项的点击事件切换到对应的Fragment。

以下是一个简单的示例代码：

<!-- activity_main.xml -->
<android.support.design.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        app:menu="@menu/navigation" />

</android.support.design.widget.CoordinatorLayout>

// MainActivity.java
public class MainActivity extends AppCompatActivity {

    private BottomNavigationView mNavigationView;

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

        mNavigationView = findViewById(R.id.navigation);
        mNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                switch (item.getItemId()) {
                    case R.id.navigation_home:
                        switchFragment(new HomeFragment());
                        return true;
                    case R.id.navigation_dashboard:
                        switchFragment(new DashboardFragment());
                        return true;
                    case R.id.navigation_notifications:
                        switchFragment(new NotificationsFragment());
                        return true;
                }
                return false;
            }
        });

        switchFragment(new HomeFragment());
    }

    private void switchFragment(Fragment fragment) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.replace(R.id.container, fragment);
        transaction.commit();
    }
}

// HomeFragment.java
public class HomeFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_home, container, false);
        // TODO: 初始化页面内容
        return view;
    }
}