Sending SMS programmatically without opening message app

You can send messages from your application through this:

public void sendSMS(String phoneNo, String msg) {
    try {      
        SmsManager smsManager = SmsManager.getDefault();
        smsManager.sendTextMessage(phoneNo, null, msg, null, null);    
        Toast.makeText(getApplicationContext(), "Message Sent",
                Toast.LENGTH_LONG).show();
    } catch (Exception ex) {
        Toast.makeText(getApplicationContext(),ex.getMessage().toString(),
                Toast.LENGTH_LONG).show();
        ex.printStackTrace();
    } 
}

Also, you need to give SEND_SMS permission in AndroidManifest.xml to send a message

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

Yes, found the answer to my own question :)

Use the following code for the same :

 SmsManager sms = SmsManager.getDefault();
                     sms.sendTextMessage(srcNumber, null, message, null, null);

This requires the following permission to be declared on the android manifest xml.

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

Sending sms with permission request :

Add In manifest :

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

Add Java Function :

void sendSmsMsgFnc(String mblNumVar, String smsMsgVar)
{
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.SEND_SMS) == PackageManager.PERMISSION_GRANTED)
    {
        try
        {
            SmsManager smsMgrVar = SmsManager.getDefault();
            smsMgrVar.sendTextMessage(mblNumVar, null, smsMsgVar, null, null);
            Toast.makeText(getApplicationContext(), "Message Sent",
                    Toast.LENGTH_LONG).show();
        }
        catch (Exception ErrVar)
        {
            Toast.makeText(getApplicationContext(),ErrVar.getMessage().toString(),
                    Toast.LENGTH_LONG).show();
            ErrVar.printStackTrace();
        }
    }
    else
    {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
        {
            requestPermissions(new String[]{Manifest.permission.SEND_SMS}, 10);
        }
    }

}

public void sendLongSMS() {
    String phoneNumber = "0123456789";
    String message = "Hello World! Now we are going to demonstrate " + 
        "how to send a message with more than 160 characters from your Android application.";
    SmsManager smsManager = SmsManager.getDefault();
    ArrayList<String> parts = smsManager.divideMessage(message); 
    smsManager.sendMultipartTextMessage(phoneNumber, null, parts, null, null);
}

and don't forget to add

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