Creating your first HTML-based AIR application with the AIR SDK

Create the project files
Create the AIR application descriptor file
Create the application HTML page
Test the application
Create the AIR installation file
Next Steps

For a quick, hands-on illustration of how Adobe® AIR® works, use these instructions to create and package a simple HTML-based AIR “Hello World” application.

To begin, you must have installed the runtime and set up the AIR SDK. You will use the AIR Debug Launcher (ADL) and the AIR Developer Tool (ADT) in this tutorial. ADL and ADT are command-line utility programs and can be found in the bin directory of the AIR SDK (see Installing the AIR SDK). This tutorial assumes that you are already familiar with running programs from the command line and know how to set up the necessary path environment variables for your operating system.

Note: If you are an Adobe® Dreamweaver® user, read Create your first HTML-based AIR application with Dreamweaver.

Note: HTML-based AIR applications can only be developed for the desktop and the extendedDesktop profiles. The mobile profile is not supported.

Create the project files

Every HTML-based AIR project must contain the following two files: an application descriptor file, which specifies the application metadata, and a top-level HTML page. In addition to these required files, this project includes a JavaScript code file, AIRAliases.js, that defines convenient alias variables for the AIR API classes.

Create a directory named HelloWorld to contain the project files.
Create an XML file, named HelloWorld-app.xml.
Create an HTML file named HelloWorld.html.
Copy AIRAliases.js from the frameworks folder of the AIR SDK to the project directory.

Create the AIR application descriptor file

To begin building your AIR application, create an XML application descriptor file with the following structure:

<application xmlns="..."> 
    <id>…</id> 
    <versionNumber>…</versionNumber> 
    <filename>…</filename> 
    <initialWindow> 
        <content>…</content> 
        <visible>…</visible> 
        <width>…</width> 
        <height>…</height> 
    </initialWindow> 
</application>

Open the HelloWorld-app.xml for editing.
Add the root <application> element, including the AIR namespace attribute:

<application xmlns="http://ns.adobe.com/air/application/2.7"> The last segment of the namespace, “2.7”, specifies the version of the runtime required by the application.
Add the <id> element:

<id>examples.html.HelloWorld</id> The application ID uniquely identifies your application along with the publisher ID (which AIR derives from the certificate used to sign the application package). The application ID is used for installation, access to the private application file-system storage directory, access to private encrypted storage, and interapplication communication.
Add the <versionNumber> element:

<versionNumber>0.1</versionNumber> Helps users to determine which version of your application they are installing.

Note: If you are using AIR 2, or earlier, you must use the <version> element instead of the <versionNumber> element.
Add the <filename> element:

<filename>HelloWorld</filename> The name used for the application executable, install directory, and other references to the application in the operating system.
Add the <initialWindow> element containing the following child elements to specify the properties for your initial application window:

<content>HelloWorld.html</content> Identifies the root HTML file for AIR to load.

<visible>true</visible> Makes the window visible immediately.

<width>400</width> Sets the window width (in pixels).

<height>200</height> Sets the window height.

Save the file. The completed application descriptor file should look like the following:

<?xml version="1.0" encoding="UTF-8"?> 
<application xmlns="http://ns.adobe.com/air/application/2.7"> 
    <id>examples.html.HelloWorld</id> 
    <versionNumber>0.1</versionNumber> 
    <filename>HelloWorld</filename> 
    <initialWindow> 
        <content>HelloWorld.html</content> 
        <visible>true</visible> 
        <width>400</width> 
        <height>200</height> 
    </initialWindow> 
</application>

This example only sets a few of the possible application properties. For the full set of application properties, which allow you to specify such things as window chrome, window size, transparency, default installation directory, associated file types, and application icons, see AIR application descriptor files.

Create the application HTML page

You now need to create a simple HTML page to serve as the main file for the AIR application.

Open the HelloWorld.html file for editing. Add the following HTML code:

<html> 
<head> 
    <title>Hello World</title> 
</head> 
<body onLoad="appLoad()"> 
    <h1>Hello World</h1> 
</body> 
</html>

In the <head> section of the HTML, import the AIRAliases.js file:
```
<script src="AIRAliases.js" type="text/javascript"></script>
```
AIR defines a property named runtime on the HTML window object. The runtime property provides access to the built-in AIR classes, using the fully qualified package name of the class. For example, to create an AIR File object you could add the following statement in JavaScript:
```
var textFile = new runtime.flash.filesystem.File("app:/textfile.txt");
```
The AIRAliases.js file defines convenient aliases for the most useful AIR APIs. Using AIRAliases.js, you could shorten the reference to the File class to the following:
```
var textFile = new air.File("app:/textfile.txt");
```
Below the AIRAliases script tag, add another script tag containing a JavaScript function to handle the onLoad event:
```
<script type="text/javascript"> 
function appLoad(){ 
    air.trace("Hello World"); 
} 
</script>
```
The appLoad() function simply calls the air.trace() function. The trace message print to the command console when you run the application using ADL. Trace statements can be very useful for debugging.
Save the file.

Your HelloWorld.html file should now look like the following:

<html> 
<head> 
    <title>Hello World</title> 
    <script type="text/javascript" src="AIRAliases.js"></script> 
    <script type="text/javascript"> 
        function appLoad(){ 
            air.trace("Hello World"); 
        }  
    </script> 
</head> 
<body onLoad="appLoad()"> 
    <h1>Hello World</h1> 
</body> 
</html>

Test the application

To run and test the application from the command line, use the AIR Debug Launcher (ADL) utility. The ADL executable can be found in the bin directory of the AIR SDK. If you haven’t already set up the AIR SDK, see Installing the AIR SDK.

Open a command console or shell. Change to the directory you created for this project.
Run the following command:
```
adl HelloWorld-app.xml
```
An AIR window opens, displaying your application. Also, the console window displays the message resulting from the air.trace() call.

For more information, see AIR application descriptor files.

Create the AIR installation file

When your application runs successfully, you can use the ADT utility to package the application into an AIR installation file. An AIR installation file is an archive file that contains all the application files, which you can distribute to your users. You must install Adobe AIR before installing a packaged AIR file.

To ensure application security, all AIR installation files must be digitally signed. For development purposes, you can generate a basic, self-signed certificate with ADT or another certificate generation tool. You can also buy a commercial code-signing certificate from a commercial certificate authority such as VeriSign or Thawte. When users install a self-signed AIR file, the publisher is displayed as “unknown” during the installation process. This is because a self-signed certificate only guarantees that the AIR file has not been changed since it was created. There is nothing to prevent someone from self-signing a masquerade AIR file and presenting it as your application. For publicly released AIR files, a verifiable, commercial certificate is strongly recommended. For an overview of AIR security issues, see AIR security (for ActionScript developers) or AIR security (for HTML developers).

Generate a self-signed certificate and key pair

From the command prompt, enter the following command (the ADT executable is located in the bin directory of the AIR SDK):

adt -certificate -cn SelfSigned 1024-RSA sampleCert.pfx samplePassword

ADT generates a keystore file named sampleCert.pfx containing a certificate and the related private key.

This example uses the minimum number of attributes that can be set for a certificate. The key type must be either 1024-RSA or 2048-RSA (see Signing AIR applications).

Create the AIR installation file

From the command prompt, enter the following command (on a single line):

adt -package -storetype pkcs12 -keystore sampleCert.pfx HelloWorld.air 
HelloWorld-app.xml HelloWorld.html AIRAliases.js

You will be prompted for the keystore file password.

The HelloWorld.air argument is the AIR file that ADT produces. HelloWorld-app.xml is the application descriptor file. The subsequent arguments are the files used by your application. This example only uses two files, but you can include any number of files and directories. ADT verifies that the main content file, HelloWorld.html is included in the package, but if you forget to include AIRAliases.js, then your application simply won’t work.

After the AIR package is created, you can install and run the application by double-clicking the package file. You can also type the AIR filename as a command in a shell or command window.

Next Steps

In AIR, HTML and JavaScript code generally behaves the same as it would in a typical web browser. (In fact, AIR uses the same WebKit rendering engine used by the Safari web browser.) However, there are some important differences that you must understand when you develop HTML applications in AIR. For more information on these differences, and other important topics, see Programming HTML and JavaScript.