Android Toolber Back Button Example

1/  Add toolbar xml 

<androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbarId"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:elevation="4dp"
    app:menu="@menu/menu"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"/>


<TextView
    android:id="@+id/textViewId"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Welcome to MainActivity2"
    android:layout_gravity="center"
    android:textStyle="bold"
    android:textSize="30dp"
    android:layout_marginTop="200dp"/>

1/  Create Menu type asset folder and create a menu on "res"

<item
    android:id="@+id/itemArrowBack"
    android:title="Item"
    android:icon="@drawable/baseline_arrow_back_24"/>

1/  Add and manage toolbar on Java

package com.sazidnayeb.practiceactivity;

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

public class MainActivity2 extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
    }

    @Override
    public boolean onSupportNavigateUp() {
        onBackPressed();
        return true;
    }
}