//Getting intent and PendingIntent instance
Intent intent=new Intent(getApplicationContext(),MainActivity.class);
PendingIntent pi=PendingIntent.getActivity(getApplicationContext(), 0, intent,0);

//Get the SmsManager instance and call the sendTextMessage method to send message				
SmsManager sms=SmsManager.getDefault();
sms.sendTextMessage("8802177690", null, "hello TheDeveloperBlog", pi,null);

<RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginRight="20dp"
        android:ems="10" />

    <EditText
        android:id="@+id/editText2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText1"
        android:layout_below="@+id/editText1"
        android:layout_marginTop="26dp"
        android:ems="10"
        android:inputType="textMultiLine" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText1"
        android:layout_alignBottom="@+id/editText1"
        android:layout_toLeftOf="@+id/editText1"
        android:text="Mobile No:" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText2"
        android:layout_alignBottom="@+id/editText2"
        android:layout_alignLeft="@+id/textView1"
        android:text="Message:" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText2"
        android:layout_below="@+id/editText2"
        android:layout_marginLeft="34dp"
        android:layout_marginTop="48dp"
        android:text="Send SMS" />

</RelativeLayout>

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

<?xml version="1.0" encoding="utf-8"?>
<manifest 
xmlns:androclass="http://schemas.android.com/apk/res/android"
    package="com.example.sendsms"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

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

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.sendsms.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

package com.example.sendsms;

import android.os.Bundle;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.Intent;
import android.telephony.SmsManager;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

	EditText mobileno,message;
	Button sendsms;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        mobileno=(EditText)findViewById(R.id.editText1);
        message=(EditText)findViewById(R.id.editText2);
        sendsms=(Button)findViewById(R.id.button1);
        
	//Performing action on button click
        sendsms.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				String no=mobileno.getText().toString();
				String msg=message.getText().toString();
				
				//Getting intent and PendingIntent instance
				Intent intent=new Intent(getApplicationContext(),MainActivity.class);
				PendingIntent pi=PendingIntent.getActivity(getApplicationContext(), 0, intent,0);
				
				//Get the SmsManager instance and call the sendTextMessage method to send message
				SmsManager sms=SmsManager.getDefault();
				sms.sendTextMessage(no, null, msg, pi,null);
				
				Toast.makeText(getApplicationContext(), "Message Sent successfully!",
					Toast.LENGTH_LONG).show();
			}
		});
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    
}