SMS Messaging

 <uses-feature
        android:name="android.hardware.telephony"
        android:required="false" />

 <uses-permission android:name="android.permission.SEND_SMS"/>
 <uses-permission android:name="android.permission.RECEIVE_SMS"/>
 <uses-permission android:name="android.permission.READ_SMS"/>

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.SmsMessage;
import android.widget.EditText;
import android.widget.Toast;

public class SmsReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        Bundle bundle = intent.getExtras();
        if (bundle != null) {

            Object[] pdus = (Object[]) bundle.get("pdus");

            for (Object pdu : pdus) {

                SmsMessage sms = SmsMessage.createFromPdu((byte[]) pdu);
                String message = sms.getMessageBody();
                String sender = sms.getOriginatingAddress();

                String received_sms="SMS from: " + sender + "\nMessage: " + message;

                Toast.makeText(context,
                        "SMS from: " + sender + "\nMessage: " + message,
                        Toast.LENGTH_LONG).show();
            }
        }
    }
}

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import android.Manifest;
import android.content.pm.PackageManager;
import android.telephony.SmsManager;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

public class MainActivity extends AppCompatActivity {

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

        EditText phone = findViewById(R.id.etPhone);
        EditText message = findViewById(R.id.etMessage);
        Button send = findViewById(R.id.btnSend);

        send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String phoneNo = phone.getText().toString();
                String msg = message.getText().toString();

                try {
                    SmsManager smsManager = SmsManager.getDefault();
                    smsManager.sendTextMessage(phoneNo, null, msg, null, null);
                    Toast.makeText(getApplicationContext(),
                            "SMS Sent Successfully",
                            Toast.LENGTH_LONG).show();
                } catch (Exception e) {
                    Toast.makeText(getApplicationContext(),
                            "SMS Failed, please try again",
                            Toast.LENGTH_LONG).show();
                }
            }
        });

        if (ContextCompat.checkSelfPermission(this, Manifest.permission.SEND_SMS)
                != PackageManager.PERMISSION_GRANTED) {

            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.SEND_SMS,
                            Manifest.permission.RECEIVE_SMS,
                            Manifest.permission.READ_SMS}, 1);
        }
    }
}