android: BottomNavigationView +viewpager2 联动

一，代码：

xml:

activity

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.Bottom2Activity">

    <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:itemTextColor="@menu/nav_item_text_selector"
        app:itemIconTint="@menu/nav_item_text_selector"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/bottom_nav_menu" />

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewpager2bottom"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/nav_view"
        />



</androidx.constraintlayout.widget.ConstraintLayout>

菜单:

<?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="首页" />

    <item
        android:id="@+id/navigation_dashboard"
        android:icon="@drawable/ic_dashboard_black_24dp"
        android:title="面板" />

    <item
        android:id="@+id/navigation_notifications"
        android:icon="@drawable/ic_notifications_black_24dp"
        android:title="消息" />

</menu>

菜单项的颜色

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="#222222" android:state_checked="true"
        android:title="selected" />
    <item android:color="#D3D3D3"
        android:title="notselected" />
</selector>

java:

package com.example.okdemo1.activity;

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

import androidx.activity.EdgeToEdge;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.fragment.app.Fragment;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import androidx.viewpager2.widget.ViewPager2;

import com.example.okdemo1.R;
import com.example.okdemo1.adapter.FragAdapter;
import com.example.okdemo1.databinding.ActivityBottomBinding;
import com.example.okdemo1.fragment.Cate1Fragment;
import com.example.okdemo1.fragment.Cate2Fragment;
import com.example.okdemo1.fragment.Cate3Fragment;
import com.google.android.material.bottomnavigation.BottomNavigationView;
import com.google.android.material.navigation.NavigationBarView;

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

public class Bottom2Activity extends AppCompatActivity {

    private List<Fragment> fragmentList = new ArrayList<>();  //fragment的列表
    private ViewPager2 vp_content;            //viewpager2

    private BottomNavigationView bottomNavigationView;    //底部导航栏

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_bottom2);

        //填充viewpager2的内容

        //添加fragment到列表
        fragmentList.add(new Cate1Fragment());
        fragmentList.add(new Cate2Fragment());
        fragmentList.add(new Cate3Fragment());
        //创建adapter
        FragAdapter viewPagerAdapter=new FragAdapter(this,fragmentList);//创建适配器对象

        //得到viewpager,并为它设置adapter
        vp_content = findViewById(R.id.viewpager2bottom);
        vp_content.setAdapter(viewPagerAdapter); // 设置翻页视图的适配器
        vp_content.setCurrentItem(0);

        bottomNavigationView = findViewById(R.id.nav_view);
        //底部导航栏的处理
        //重点 设置 bottomNavigationView 的item 的点击事件 设置viewPager2的联动
        bottomNavigationView.setOnItemSelectedListener(new NavigationBarView.OnItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                int itemId = item.getItemId();
                Log.d("click","当前点击了item:"+itemId);
                if (itemId == R.id.navigation_home) {
                    // 处理逻辑
                    vp_content.setCurrentItem(0);
                } else if (itemId == R.id.navigation_dashboard) {
                    // 其他逻辑
                    vp_content.setCurrentItem(1);
                } else {
                    // 默认情况
                    vp_content.setCurrentItem(2);
                }
                return true;
            }
        });


        //重点 实现viewpager2滑动的时候 联动 bottomNavigationView的selectedItem
        vp_content.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
            @Override
            public void onPageSelected(int position) {
                super.onPageSelected(position);
                switch (position){
                    case 0:
                        bottomNavigationView.setSelectedItemId(R.id.navigation_home);
                        break;
                    case 1:
                        bottomNavigationView.setSelectedItemId(R.id.navigation_dashboard);
                        break;
                    case 2:
                        bottomNavigationView.setSelectedItemId(R.id.navigation_notifications);
                        break;
                }
            }
        });
        
    }
}

adapter

package com.example.okdemo1.adapter;

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

import java.util.List;

public class FragAdapter extends FragmentStateAdapter {

    private List<Fragment> mFragments;

    public FragAdapter(FragmentActivity fa,List<Fragment> fragments) {
        super(fa);
        mFragments=fragments;
    }

    @Override
    public Fragment createFragment(int position) {
        return  mFragments.get(position);
    }

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

}

fragment没有功能，不再贴代码

 

二，测试效果: