Android Custom Toolbar Back Button Example

1/  XML - Create a custom toolbar

<?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=".MainActivity">

    <LinearLayout
        android:paddingHorizontal="16sp"
        android:gravity="center_vertical"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" >

        <ImageView
            android:id="@+id/backbtn"
            android:layout_width="24dp"
            android:layout_height="24dp"
            android:src="@drawable/baseline_arrow_back_24"/>
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

1/ Activiy - Use Finish() at setOnclickListhener to go back

package com.tutorialb.customtoolbar;

import android.os.Bundle;
import android.widget.ImageView;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });

        ImageView backBtn = findViewById(R.id.backbtn);

        backBtn.setOnClickListener(v -> {
            finish();
        });

    }
}