Android使用Viewpager2+Fragment+BottomNavigationView实现底部菜单栏的切换模块的样式。

效果图：

实现步骤：

1.首先在app的builde文件中引用ViewPager2

implementation 'androidx.viewpager2:viewpager2:1.0.0-alpha01'

2.添加首页的布局xml

<?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”>

    <androidx.viewpager2.widget.ViewPager2
        android:id=”@+id/mainViewPager”
        android:layout_width=”match_parent”
        android:layout_height=”match_parent”
        android:layout_above=”@+id/navigationView” />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id=”@+id/navigationView”
        android:layout_width=”match_parent”
        android:layout_height=”wrap_content”
        android:layout_alignParentBottom=”true”
        android:background=”#FFFFFF” />

</RelativeLayout>

3.创建home Activity页面

package com.example.tasklayoutdemo.tab;

import android.os.Bundle;
import android.view.MenuItem;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager2.widget.ViewPager2;

import com.example.tasklayoutdemo.R;
import com.google.android.material.bottomnavigation.BottomNavigationView;
import com.google.android.material.bottomnavigation.LabelVisibilityMode;

import org.jetbrains.annotations.NotNull;

import java.util.ArrayList;
import java.util.List;

public class HomeActivity extends AppCompatActivity {

    private ViewPager2 mainViewPager;
    private BottomNavigationView navigationView;

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

        initView();
        initDate();
    }

    private void initView() {
        mainViewPager = findViewById(R.id.mainViewPager);
        navigationView = findViewById(R.id.navigationView);
    }

    private void initDate() {
        List<Fragment> fragmentArr = new ArrayList<Fragment>();
        fragmentArr.add(new HomeShouYeFragment());
        fragmentArr.add(new HomeInfoFragment());
        fragmentArr.add(new HomeFindFragment());
        fragmentArr.add(new HomeMineFragment());

        navigationView.getMenu().add(0, 0, 1, "首页").setIcon(R.drawable.tab_1);
        navigationView.getMenu().add(0, 1, 1, "消息").setIcon(R.drawable.tab_2);
        navigationView.getMenu().add(0, 2, 1, "园地").setIcon(R.drawable.tab_3);
        navigationView.getMenu().add(0, 3, 1, "我的").setIcon(R.drawable.tab_4);
        /**
         * 否禁止用户滑动页面
         * */
        mainViewPager.setUserInputEnabled(false);
        /**
         * 设置ViewPager2的滑动监听事件
         * isUserInputEnabled = true 时
         * */
        mainViewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                super.onPageScrolled(position, positionOffset, positionOffsetPixels);
            }

            @Override
            public void onPageSelected(int position) {
                super.onPageSelected(position);
                //设置导航栏选中位置
                navigationView.getMenu().getItem(position).setChecked(true);
            }

            @Override
            public void onPageScrollStateChanged(int state) {
                super.onPageScrollStateChanged(state);
            }
        });
        mainViewPager.setAdapter(new HomePagerAdapter(this, fragmentArr));
        navigationView.setLabelVisibilityMode(LabelVisibilityMode.LABEL_VISIBILITY_LABELED);
        /**
         * 设置导航栏菜单项Item选中监听
         * */
        navigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull @NotNull MenuItem item) {
                mainViewPager.setCurrentItem(item.getItemId());
                return true;
            }
        });


    }
}

4.创建对应的Fragment页面（示例中需创建四个，我贴出来一个代码，其他的一样）

package com.example.tasklayoutdemo.tab;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.example.tasklayoutdemo.R;

import org.jetbrains.annotations.NotNull;

public class HomeInfoFragment extends Fragment {

    private TextView tv_content;
    private View view;

    @Nullable
    @org.jetbrains.annotations.Nullable
    @Override
    public View onCreateView(@NonNull @NotNull LayoutInflater inflater, @Nullable @org.jetbrains.annotations.Nullable ViewGroup container, @Nullable @org.jetbrains.annotations.Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.shouye_fragment, container, false);
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable @org.jetbrains.annotations.Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        tv_content = view.findViewById(R.id.tv_content);
        tv_content.setText("我是Fragment，消息....");
    }

}

5.创建 HomePagerAdapter

package com.example.tasklayoutdemo.tab;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;

import org.jetbrains.annotations.NotNull;

import java.util.List;

public class HomePagerAdapter extends FragmentStateAdapter {

    private List<Fragment> fragments;

    public HomePagerAdapter(@NonNull @NotNull FragmentActivity fragmentActivity, List<Fragment> fragments) {
        super(fragmentActivity);
        this.fragments = fragments;
    }


    @NonNull
    @NotNull
    @Override
    public Fragment createFragment(int position) {
        return fragments.get(position);
    }

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

6.添加导航栏图标

完成，运行即可

7.进阶

其中app:itemTextColor=”@drawable/main_bottom”为设置按钮选中与未选中时字体的颜色选择

app:itemIconTint=”@drawable/main_bottom”为设置按钮选中与未选中时图标的颜色选择

main_bottom.xml文件为：

<?xml version=”1.0″ encoding=”utf-8″?>
<selector xmlns:android=”http://schemas.android.com/apk/res/android”>
    <item android:color=”@android:color/holo_red_light” android:state_checked=”true” />
    <item android:color=”@color/black” android:state_checked=”false” />
</selector>