Add a Back Button to Action Bar Android Studio (Kotlin)

      DESCRIPTION      

In this tutorial we will add a back button in action bar, when it is clicked it will go to previous activity(the app will close if this was launcher activity). We will go from main activity to new activity by clicking button in main activity. In new activity we will add a back button to actionbar when that button is clicked the main activity will appear...

      VIDEO      

      SOURCE CODE      

Step 1: Create a new Project or open new project

Step 2: Create New Activity File>New>Activity>EmptyActivity

Step 3: Code:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/startActBtn"
        android:text="New Activity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

MainActivity.kt

package com.blogspot.devofandroid.myapplication

import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //button
        val mStartActBtn = findViewById<Button>(R.id.startActBtn)
        //handle button click
        mStartActBtn.setOnClickListener {
            //start activity intent
            startActivity(Intent(this@MainActivity, NewActivity::class.java))
        }

    }

}

activity_new.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    android:gravity="center"
    tools:context=".NewActivity">

    <TextView
        android:text="Click back buttoon of actionbar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

NewActivity.kt

package com.blogspot.devofandroid.myapplication

import android.support.v7.app.AppCompatActivity
import android.os.Bundle

class NewActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_new)

        //actionbar
        val actionbar = supportActionBar
        //set actionbar title
        actionbar!!.title = "New Activity"
        //set back button
        actionbar.setDisplayHomeAsUpEnabled(true)
        actionbar.setDisplayHomeAsUpEnabled(true)
    }

    override fun onSupportNavigateUp(): Boolean {
        onBackPressed()
        return true
    }
}

Step 4: Run Project

Output