How to Send Data Back to MainActivity in Android using Kotlin?

As there are many methods to send the data, but in this article, we will use startActivityForResult() method. Here we need to launch a child activity using startActivityForResult() method. Then from child activity, we can easily send data back to Main Activity. 

Example:

Note: To implement it in java refer to this article: How to send data from one activity to second activity using Java

Step by Step Implementation

Step 1: Create new project in android using kotlin

Step 2: Create XML layout for MainActivity

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">

    <ImageView
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:src="@drawable/ic_geeksforgeeks"
        app:layout_constraintBottom_toTopOf="@+id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Text View"
        android:textColor="#7CB342"
        android:textSize="20dp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.303" />

</androidx.constraintlayout.widget.ConstraintLayout>

Step 3: Below is the code for MainActivity.kt file

Kotlin

package com.ayush.gfg_exit

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import kotlin.properties.Delegates

class MainActivity : AppCompatActivity() {

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

        findViewById<Button>(R.id.btnMain).setOnClickListener {
            val intent = Intent(this, ChildActivity::class.java)
             // 0 is request code
            startActivityForResult(intent, 0)
        }
    }

      // this called after child activity finishes.
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        if (requestCode == 0) {
            if (resultCode == RESULT_OK) {
                // Get the result from intent
                val result = intent.getStringExtra("result")
                // set the result to the text view
                findViewById<TextView>(R.id.textView).text = result
            }
        }
    }
}

Step 4: XML for child activity

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=".ChildActivity">

    <EditText
        android:id="@+id/etChild"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="15dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.444"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.263" />

    <Button
        android:id="@+id/btnChild"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send data to MainActivity"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.496"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etChild"
        app:layout_constraintVertical_bias="0.241" />

</androidx.constraintlayout.widget.ConstraintLayout>

Step 5: Following code for ChildActivity.kt file

Kotlin

package com.ayush.gfg_exit

import android.app.Activity
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText

class ChildActivity : AppCompatActivity() {
    lateinit var etChild: EditText
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_child)

        etChild = findViewById(R.id.etChild)
        findViewById<Button>(R.id.btnChild).setOnClickListener {
            val result = etChild.text.toString()
            val intent = Intent()
            intent.putExtra("result", result)
            setResult(Activity.RESULT_OK, intent)
            finish()
        }
    }
}

So our app is ready.

Output: