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

This example demonstrates how do I send emails using gmail from my Android application.
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:padding="4dp"
   tools:context=".MainActivity"
   android:orientation="vertical">

   <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:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:id="@+id/editTextSubject"/>

   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Message"/>

   <EditText
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:id="@+id/editTextMessage"
      android:lines="4"/>

   <Button
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:id="@+id/buttonSend"
      android:text="Send" />
</LinearLayout>
Step 3 − Add the following code to src/MainActivity.java
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity{

   EditText editTextMail, editTextSubject, editTextMessage;
   Button buttonSend;
   String email, subject, message;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);

      editTextMail = findViewById(R.id.editTextMail);
      editTextSubject = findViewById(R.id.editTextSubject);
      editTextMessage = findViewById(R.id.editTextMessage);

      buttonSend = findViewById(R.id.buttonSend);

      buttonSend.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            getData();
            Intent intent = new Intent(Intent.ACTION_SEND);
            intent.putExtra(Intent.EXTRA_EMAIL, new String(email));
            intent.putExtra(Intent.EXTRA_SUBJECT, subject);
            intent.putExtra(Intent.EXTRA_TEXT, message);

            intent.setType("message/rfc822");
            startActivity(Intent.createChooser(intent, "Select email"));
         }
      });
   }

   private void getData() {
      email = editTextMail.getText().toString();
      subject = editTextSubject.getText().toString();
      message = editTextMessage.getText().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.sample">

   <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 Run  Icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –