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

Last Updated : 06 Dec, 2021

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()
        }
    }
}