Creating Your First Android Application (SMS App)

                  Beginning Android tutorial series covered the overview of the Android platform. If you haven't seen it yet, please take some time to read it before reading this article.

                  In this article, you will develop your first Android application. You will learn how to send SMS programmatically within an Android application.

NOTE: This tutorial assumes that you are familiar with Java programming and IDE's like Eclipse and NetBeans.

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Brief Contents

1. The Four Components of Android
2. Creating The SMS Application
• Obtaining The Required Tools
• Developing SendingSMS project

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The Four Components of Android

Your Android projects should contain at least one class that is derived from one of these components:

• Activity - If your Android application has a UI, you must create one class that extends this component. You will learn how to create an Activity in this article.
• Service - If your Android application has a long running task, you should do it in the background and not in the UI thread. This class provides the facility to make a task run in the background.
• BroadcastReceiver - If your Android application will receive and respond to global events such as the sending and delivery of SMS, your class must be registered as a subclass of this component. You will learn how to use this component to get feedback after sending SMS.
• ContentProvider - If your Android application has data that you wants to share with other Android applications, you should create and implement this component.

For the detailed look at the Android Build process please refer to Android documentation.

Creating The SMS Application

Android development has four phases. Below is a diagram of Android development process:

Obtaining The Required Tools

Before you can start creating Android application, you must setup your development environment first. You will need the following to develop our SMS application:

• Android SDK
• Eclipse (Helios or greater)

Note: You need to install at least the Android 1.6 platform for this tutorial.

See Android Installation Instructions and System Requirements for more information and watch this video to learn how to setup your development environment for the first time on Windows. 

I use Windows 7, Java 7, Eclipse Indigo for Java Developers, ADT and Android SDK revision 17 in this screencast.

Developing The SMS Project

SMS messaging is one of the killer applications on Android or any mobile phones today. Let's create your first simple and practical Android project. I assume that you are already familiar with Java programming; I will not explain each line of code in detail.

Follow these steps:

1. Start your Eclipse IDE

2. Go to File -> New -> Project

3. Select Android Project in the New Project dialog

4. Complete the New Android Project wizard.

5. Open main.xml (located in <your project's name>/res/layout) and replace its contents with the code below:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
    <EditText
        android:id="@+id/editRecipient"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="14dp"
        android:hint="@string/recipientHint"
        android:inputType="phone" />
    <EditText
        android:id="@+id/editMessage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_marginBottom="17dp"
        android:layout_toLeftOf="@+id/sendButton"
        android:hint="@string/messageBodyHint" >
    </EditText>
    <Button
        android:id="@+id/sendButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignTop="@+id/editMessage"
        android:onClick="send"
        android:text="@string/sendButtonText" />
</RelativeLayout>

Note: I used RelativeLayout here because I need to align each common form component relative to the other components.

6. Open SMSActivity.java (located in <your project's name>/src/<your package name>) and add the following code:

public void send(android.view.View view) {
final android.widget.EditText recipient = (android.widget.EditText) findViewById(R.id.editRecipient);
final android.widget.EditText message = (android.widget.EditText) findViewById(R.id.editMessage);
final android.telephony.SmsManager smsManager = android.telephony.SmsManager.getDefault();
final String addr = recipient.getText().toString();
final String text = message.getText().toString();
smsManager.sendTextMessage(addr, null, text, null, null);
recipient.setText("");
message.setText("");
}

7. To allow our application to send SMS, add the following permission to AndroidManifest.xml (located in your project's root directory):

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

8. That's it. Deploy and run the project.

How It Works

Steps 1 to 4 show you how to create a new Android application in Eclipse. Steps 5 to 7 cover the code that will enable your new application to send SMS: step 5 changes the layout of your application's UI; step 6 includes the actual code that sends an SMS, and; step 7 includes a code snippet that informs our users about the permissions the application needs to send SMS. Step 8 shows you how to run the application.

The application uses the built-in Android telephony API class `android.telephony.SmsManager` to send SMS; for more information, see: documentation of SmsManager API.