How can I send emails using gmail from my Android application using Kotlin?

This example demonstrates how to send emails using gmail from my Android application using Kotlin.
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
Step 2 − Add the following code to res/layout/activity_main.xml.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical"
   android:padding="8dp"
   tools:context=".MainActivity">
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Recipient email!" />
   <EditText
      android:id="@+id/editTextMail"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" />
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Subject" />
   <EditText
      android:id="@+id/editTextSubject"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" />
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Message" />
   <EditText
      android:id="@+id/editTextMessage"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:lines="4" />
   <Button
      android:id="@+id/buttonSend"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="Send" />
</LinearLayout>
Step 3 − Add the following code to MainActivity.kt
import android.content.Intent
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   lateinit var editTextMail: EditText
   lateinit var editTextSubject: EditText
   lateinit var editTextMessage: EditText
   lateinit var buttonSend: Button
   lateinit var email: String
   lateinit var subject: String
   lateinit var message: String
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      editTextMail = findViewById(R.id.editTextMail)
      editTextSubject = findViewById(R.id.editTextSubject)
      editTextMessage = findViewById(R.id.editTextMessage)
      buttonSend = findViewById(R.id.buttonSend)
      buttonSend.setOnClickListener {
         getData()
         val intent = Intent(Intent.ACTION_SEND)
         intent.putExtra(Intent.EXTRA_EMAIL, email)
         intent.putExtra(Intent.EXTRA_SUBJECT, subject)
         intent.putExtra(Intent.EXTRA_TEXT, message)
         intent.type = "message/rfc822"
         startActivity(Intent.createChooser(intent, "Select email"))
      }
   }
   private fun getData() {
      email = editTextMail.text.toString()
      subject = editTextSubject.text.toString()
      message = editTextMessage.text.toString()
   }
}
Step 4 − Add the following code to androidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.kotlipapp">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −
Click here to download the project code.