Android Fragment实现顶部、底部导航栏

前言

无论是顶部还是底部导航栏，都是大多数APP的标配，网络上的相关实现教程也非常之多。最近回忆起以前写的小项目，发现对这块内容有些遗忘，不妨就再整理一遍代码逻辑，记录下来，方便日后查阅（指复制粘贴）。

实现的方式有很多，本文采用以下方式实现：

• 底部导航栏：Fragment + BottomNavigationView
• 顶部导航栏：Fragment + ViewPager2 + TabLayout

底部导航栏

<布局文件>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <FrameLayout
        android:id="@+id/main_page_controller"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginBottom="50dp"
        android:background="#EFEEEE"/>

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/main_navigation_bar"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:background="#ffffff"
        app:itemIconTint="@color/navigation_bar_color"
        app:itemTextColor="@color/navigation_bar_color"
        app:labelVisibilityMode="labeled"
        app:menu="@menu/navigation_items"/>

</RelativeLayout>

<menu文件>

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/home"
        android:icon="@mipmap/home"
        android:title="首页"/>
    <item
        android:id="@+id/plan"
        android:icon="@mipmap/plan"
        android:title="日程"/>
    <item
        android:id="@+id/game"
        android:icon="@mipmap/game"
        android:title="娱乐"/>
    <item
        android:id="@+id/setting"
        android:icon="@mipmap/setting"
        android:title="设置"/>
</menu>

<MainActivity.java>

public class MainActivity extends AppCompatActivity {

    private BottomNavigationView mNavigationView;

    private FragmentManager mFragmentManager;

    private Fragment[] fragments;
    private int lastFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mNavigationView = findViewById(R.id.main_navigation_bar);
        initFragment();
        initListener();
    }

    private void initFragment() {
        HomeFragment mHomeFragment = new HomeFragment();
        PlanFragment mPlanFragment = new PlanFragment();
        GameFragment mGameFragment = new GameFragment();
        SettingFragment mSettingFragment = new SettingFragment();
        fragments = new Fragment[]{mHomeFragment, mPlanFragment, mGameFragment, mSettingFragment};
        mFragmentManager = getSupportFragmentManager();
        //默认显示HomeFragment
        mFragmentManager.beginTransaction()
                .replace(R.id.main_page_controller, mHomeFragment)
                .show(mHomeFragment)
                .commit();
    }

    private void initListener() {
        mNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                switch (item.getItemId()) {
                    case R.id.home:
                        if (lastFragment != 0) {
                            MainActivity.this.switchFragment(lastFragment, 0);
                            lastFragment = 0;
                        }
                        return true;
                    case R.id.plan:
                        if (lastFragment != 1) {
                            MainActivity.this.switchFragment(lastFragment, 1);
                            lastFragment = 1;
                        }
                        return true;
                    case R.id.game:
                        if (lastFragment != 2) {
                            MainActivity.this.switchFragment(lastFragment, 2);
                            lastFragment = 2;
                        }
                        return true;
                    case R.id.setting:
                        if (lastFragment != 3) {
                            MainActivity.this.switchFragment(lastFragment, 3);
                            lastFragment = 3;
                        }
                        return true;
                }
                return false;
            }
        });
    }

    private void switchFragment(int lastFragment, int index) {
        FragmentTransaction transaction = mFragmentManager.beginTransaction();
        transaction.hide(fragments[lastFragment]);
        if (!fragments[index].isAdded()){
            transaction.add(R.id.main_page_controller,fragments[index]);
        }
        transaction.show(fragments[index]).commitAllowingStateLoss();
    }

}

<实现效果>

顶部导航栏

<布局文件>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/home_indicator"
        android:layout_width="match_parent"
        android:layout_height="30dp"
        app:tabGravity="fill" />

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/home_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

<ViewPgaer2适配器>

public class HomePagerAdapter extends FragmentStateAdapter {

    private List<String> mData = new ArrayList<>();

    public HomePagerAdapter(@NonNull FragmentActivity fragmentActivity, List<String> data) {
        super(fragmentActivity);
        mData = data;
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        return HomePageFragment.newInstance(mData.get(position));
    }

    @Override
    public int getItemCount() {
        return mData.size();
    }
}

<HomeFragment.java>

public class HomeFragment extends Fragment {

    private TabLayout mTabLayout;
    private ViewPager2 mViewPager2;
    private List<String> mData = new ArrayList<>();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_home, container, false);
        initData();
        initView(rootView);
        return rootView;
    }

    private void initView(View rootView) {
        mTabLayout = rootView.findViewById(R.id.home_indicator);
        mViewPager2 = rootView.findViewById(R.id.home_pager);
        HomePagerAdapter homePagerAdapter = new HomePagerAdapter(getActivity(), mData);
        mViewPager2.setAdapter(homePagerAdapter);
        new TabLayoutMediator(mTabLayout, mViewPager2, new TabLayoutMediator.TabConfigurationStrategy() {
            @Override
            public void onConfigureTab(@NonNull TabLayout.Tab tab, int position) {
                tab.setText(mData.get(position));
            }
        }).attach();
    }

    private void initData() {
        mData.add("页面1");
        mData.add("页面2");
        mData.add("页面3");
        mData.add("页面4");
        mData.add("页面5");
    }

}

<HomePageFragment.java>

public class HomePageFragment extends Fragment {

    private static final String ARG_PARAM1 = "param1";

    private String mParam1;

    private TextView textView;

    public HomePageFragment() {

    }

    public static HomePageFragment newInstance(String param1) {
        HomePageFragment fragment = new HomePageFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_home_page, container, false);
        textView = rootView.findViewById(R.id.home_page_tv);
        textView.setText(mParam1);
        return rootView;
    }
}

<实现效果>

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