Send SMS from Your Android Application

Use bellow code in Activity class in your own method

public void SendSMSRequest(View view) {
    String SendSMSNumber = "880xxxxxxxxxx";   

    String smsText = "Need Permission";
    String phoneNo = GetSMSNumber.toString();   

    String msg = smsText.toString();  

   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();    }
}

Use bellow code in XML 

   <Button android:layout_width="225dp"  
           android:layout_height="75dp"  
           android:text="Off Line Play"  
           android:id="@+id/button"    
           android:onClick="SendSMSRequest"
           android:textColor="#ffffff"  
           android:textStyle="bold"   
           android:textSize="21sp"  
           android:layout_above="@+id/subscribe"  
           android:layout_centerHorizontal="true"    />

Use permission in Androidmanifest
<!-- Permission:Sms Related access -->
<uses-permission android:name="android.permission.SEND_SMS" />
<uses-permission android:name="android.permission.READ_SMS" />
<uses-permission android:name="android.permission.WRITE_SMS" />