Fragment实现底部导航栏，TabLayout实现顶部导航栏，二者相互嵌套完成App基本布局框架
1.Fragment实现底部导航栏
Fragment 表示 FragmentActivity 中的行为或界面的一部分。您可以在一个 Activity 中组合多个片段，从而构建多窗格界面，并在多个 Activity 中重复使用某个片段。您可以将片段视为 Activity 的模块化组成部分，它具有自己的生命周期，能接收自己的输入事件，并且您可以在 Activity 运行时添加或移除片段（这有点像可以在不同 Activity 中重复使用的“子 Activity”）。当您将片段作为 Activity 布局的一部分添加时，其位于 Activity 视图层次结构的某个 ViewGroup 中，并且片段会定义其自己的视图布局。
第一步：创建Fragment视图
以choice包为例，ChoiceFragment用于展示布局，而ChoiceViewModel用于为ChoiceFragment准备初始化展示的数据
public class ChoiceFragment extends Fragment {
private ChoiceViewModel mViewModel;
public static ChoiceFragment newInstance() {
return new ChoiceFragment();
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_choice, container, false);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mViewModel = ViewModelProviders.of(this).get(ChoiceViewModel.class);
// TODO: Use the ViewModel
}
}
public class ChoiceViewModel extends ViewModel {
// TODO: Implement the ViewModel
private MutableLiveData<String> mText;
public ChoiceViewModel() {
mText = new MutableLiveData<>();
mText.setValue("This is home fragment");
}
public LiveData<String> getText() {
return mText;
}
}
第二步：在res目录下建立navigation文件，在里面创建mobile_navigation.xml文件，用于集中绑定视图。其中app:startDestination="@+id/navigation_home"是以navigation_home为第一个打开的活动
<?xml version="1.0" encoding="utf-8"?>
<navigation 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/mobile_navigation"
app:startDestination="@+id/navigation_home">
<fragment
android:id="@+id/navigation_home"
android:name="com.example.buttontest.ui.home.HomeFragment"
android:label="@string/title_home"
tools:layout="@layout/fragment_home" />
<fragment
android:id="@+id/navigation_attention"
android:name="com.example.buttontest.ui.dashboard.DashboardFragment"
android:label="@string/title_attention"
tools:layout="@layout/fragment_dashboard" />
<fragment
android:id="@+id/navigation_vip"
android:name="com.example.buttontest.ui.notifications.NotificationsFragment"
android:label="@string/title_vip"
tools:layout="@layout/fragment_notifications" />
<fragment
android:id="@+id/navigation_doki"
android:name="com.example.buttontest.ui.doki.DokiFragment"
android:label="@string/title_doki"
tools:layout="@layout/doki_fragment" />
<fragment
android:id="@+id/navigation_person"
android:name="com.example.buttontest.ui.person.PersonFragment"
android:label="@string/title_person"
tools:layout="@layout/person_fragment" />
</navigation>
第三步：
1.首先在所要依托的活动中加入fragment布局。BottomNavigationView是底部导航栏所需要用到的控件。
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/nav_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="?android:attr/windowBackground"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:menu="@menu/bottom_nav_menu" />
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@id/nav_view"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/mobile_navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>
2.在res目录中创建menu文件夹，同时在里面创建bottom_nav_menu.xml文件
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/navigation_home"
android:icon="@drawable/ic_home_black_24dp"
android:title="@string/title_home" />
<item
android:id="@+id/navigation_attention"
android:icon="@drawable/ic_dashboard_black_24dp"
android:title="@string/title_attention" />
<item
android:id="@+id/navigation_vip"
android:icon="@drawable/ic_notifications_black_24dp"
android:title="@string/title_vip" />
<item
android:id="@+id/navigation_doki"
android:icon="@drawable/ic_doki_foreground"
android:title="@string/title_doki" />
<item
android:id="@+id/navigation_person"
android:icon="@drawable/ic_person_foreground"
android:title="@string/title_person" />
</menu>
注意：此处所有item的id都需要和fragment的id一一对应相同，以达到顺利绑定的效果，此处有多少个item，底部导航栏就有多少个视图选项
3.在主活动代码中完成绑定
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView navView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder(
R.id.navigation_home, R.id.navigation_attention, R.id.navigation_vip,R.id.navigation_doki,R.id.navigation_person)
.build();//所有需要在底部导航栏显示的fragment都需要在此处进行绑定
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
NavigationUI.setupWithNavController(navView, navController);
}
}
由此就可以实现底部导航栏了
2.Tab页签实现顶部导航栏切换
我们只需要在需要使用Tab页签的那个fragment中绑定新的fragment，即可实现在该界面完成顶部为Tab页签，底部为fragment导航。
public class HomeFragment extends Fragment {
private HomeViewModel homeViewModel;
private LikeFragment likeFragment;//引用需要用到的fragment
private ChoiceFragment choiceFragment;
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
homeViewModel =
ViewModelProviders.of(this).get(HomeViewModel.class);
View root = inflater.inflate(R.layout.fragment_home, container, false);
homeViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
}
});
likeFragment = LikeFragment.newInstance();
choiceFragment = ChoiceFragment.newInstance();
getChildFragmentManager().beginTransaction().replace(R.id.linearLayout,choiceFragment).commit();
TabLayout tabLayout = (TabLayout)root.findViewById(R.id.tabLayout);
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
Toast.makeText(getActivity(),tab.getText(),Toast.LENGTH_SHORT).show();
if (tab.getText().equals("爱看")){
getChildFragmentManager().beginTransaction().replace(R.id.linearLayout,likeFragment).commit();
}
if (tab.getText().equals("精选")){
getChildFragmentManager().beginTransaction().replace(R.id.linearLayout,choiceFragment).commit();
}
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
return root;
}
}