How to develop cross-platform mobile apps on Linux

http://xmodulo.com/2013/12/develop-cross-platform-mobile-apps-linux.html

The last few years have witnessed dramatic growth of the mobile market, mostly driven by a large selection of applications. As consumers, we all hate to see some kind of market monopoly by any one platform. The more competition, the more innovation. As developers, we have mixed feelings about cross-platform development. Cross-platform development has several cons; poor platform integration, inflexible design, etc. On the other hand, we can reach a wider market with more consumers, and can offer uniform look and feel for our app across various platforms.
Today, almost all modern mobile platforms provide object-oriented APIs. Thus there is no reason not to build multi-platform apps. In this tutorial, we will walk you through the basics of cross-platform development. As a cross-platform SDK, we will use Titanium SDK from Appcelerator.

What do we need?

• Understanding of Java
• PC
• Android SDK
• Titanium SDK

Titanium as a development platform allows you to produce from a single source native apps for Apple iOS as well as Google Android. It uses Java as a primary language, and can work with HTML and JavaScript as well. It does not rely on WebUI, and is extensible. Modules can be written in Objective-C.
For people who are good at Java and HTML, Titanium is a good start in mobile development. To develop Android apps, you will need Android SDK and for iOS apps, Mac. Lucky for us, once you have a code, you can import it into Titanium on Mac, and compile it for iOS.
For Titanium SDK to work properly, we will need:

• Oracle Java JDK 6 or 7
• Node.js
• Android SDK and Android NDK
• At least 2 Gb of RAM

Download Titanium SDK from here (sign-up required).

When Titanium finishes downloading, go to download directory and extract it to /opt.
Next go to terminal, and set path.
Next we have to install all dependencies for Titanium SDK.
On Ubuntu or Debian, we will use apt-get:
On Fedora, use yum:
After installing dependencies, we have to relocate Titanium as follows.
Before we run Titanium SDK for the first time, we have to make a build directory for Titanium. Usually I have in my /home directory a folder named "builds" with sub folders for all my projects. Let us make a build directory.
With a build directory created, launch Titanium.

Log in with your user account created during downloading Titanium SDK, and navigate it to your build directory.

Titanium SDK's work window is connected to your account created earlier. It provides rich information and a lot of help. On the left side, we can choose between creating a new project or importing an old project. For this tutorial, we will make a new project, so select "Create Project" tab.

In a new project window, we can choose among multiple templates. For this tutorial, we will choose a default project template.

After this, we have to name the project. Put in app id and company URL. App id is inverse from company URL and ends with .appname. Our site URL is http://xmodulo.com, and our app is named "firstapp". That makes our app id "com.xmodulo.firstapp".

With the named project, we need to select Android components. I usually select all of them.

Titanium will download and configure all needed components, as well as update old ones. After downloading and installing Android components, Titanium will automatically open a working window for our project.

A work window consists of two tabs: app.js and app editor. App.js is for coding, and app editor window is used to provide app information.
With Titanium set up, let us create some simple code in app.js window to learn Titanium's basic elements.
The most important element in Titanium is a window element. Windows are nothing complicated. You can think of a window as a container of your work. For a particular application, you can add one or more windows. The next important element is a view element which is a rectangle that can hold other elements, like tag in HTML. Also important elements are tag groups and tags. How do they work? Each tag group holds one or more tags, and each tag controls windows.

Simple app build

In this part of the tutorial, we will build a simple app with only main elements. First, let us specify some basic things, like pixels. Pixel sizes are not in standard px notation, but in percentage, and are required to be written as string.
For colors we don't use names as they are in hexa-decimal RGB code.
And now using the function Titanium.UI.createWindow, we can create our first windows, and elaborate a little.
What does this code mean? It says that we pass to the createWindows function an argument with all properties. The logic behind those elements is simple.
The tagGroup is the application's root, and cannot be included in some other elements. It holds the tabs and each tab holds its own windows. Let us bring all that together, and build a simple app that demonstrates windows, tabs, and views.
Now let us create some windows and tabs.
With that, let us connect it all together into one.
After having written our code, we need to define its look. For that we will use a label element. With the label element, we can add a background wallpaper for our app, define native font and colors. Also, it allows defining the look of other elements. For our app, we will define the look of window elements. Let us make a simple label element for our app.
And how does the source code look together?

And this is what our simple app looks like when run in Android emulator.

This code is small and simple, but is a very good way to begin cross-platform development.

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