하단탭 사용법

* res > menu(폴더명 "menu"로 생성) > menu_bottom.xml 추가

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

    <item
        android:id="@+id/tab1"
        app:showAsAction="ifRoom"
        android:enabled="true"
        android:icon="@android:drawable/ic_dialog_email"
        android:title="이메일" />

    <item
        android:id="@+id/tab2"
        app:showAsAction="ifRoom"
        android:enabled="true"
        android:icon="@android:drawable/ic_dialog_info"
        android:title="정보" />

    <item
        android:id="@+id/tab3"
        app:showAsAction="ifRoom"
        android:enabled="true"
        android:icon="@android:drawable/ic_dialog_map"
        android:title="위치" />

</menu>

* Fragment1.java

package com.example.tab2;

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

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

public class Fragment1 extends Fragment {

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment1, container, false);
    }
}

* MainActivity.java

public class MainActivity extends AppCompatActivity {

    Fragment1 fragment1;
    Fragment2 fragment2;
    Fragment3 fragment3;

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

        fragment1 = new Fragment1();
        fragment2 = new Fragment2();
        fragment3 = new Fragment3();

        getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment1).commit();

        BottomNavigationView bottomNavigation = findViewById(R.id.bottom_navigation);
        bottomNavigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
                switch (menuItem.getItemId()) {
                    case R.id.tab1:
                        getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment1).commit();
                        return true;
                    case R.id.tab2:
                        getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment2).commit();
                        return true;
                    case R.id.tab3:
                        getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment3).commit();
                        return true;
                    default:
                        return false;
                }
            }
        });
    }
}

* activity_main.xml

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        android:background="@color/colorPrimary"
        app:itemIconTint="@drawable/item_color"
        app:itemTextColor="@drawable/item_color"
        app:menu="@menu/menu_bottom" />

</androidx.constraintlayout.widget.ConstraintLayout>