Mobile development technologies

Introduction

There are a number of different options when developing for a mobile device such as a phone. There are two general approaches: web development, and native application ("app") development. Each is discussed below.

Location based applications - GPS

Before considering the different development options and mobile operating systems, a word on GPS (Global Positioning System) as this is one of the most exciting developments in the mobile software world. Most contemporary smartphones, including most Android phones and many Nokias, can use GPS - a series of satellites controlled by the US - to locate you on the Earth. This is the same technology that car "satnav" (satellite navigation) systems use.

This allows the development of interesting mobile applications that use your position on the Earth to deliver information about nearby points of interest, such as pubs or restaurants, through your phone. GPS enabled phones are the most effective for these location based applications, but any phone can use the mobile phone mast system to give an approximate location on the Earth.

Mobile Web Development

One option in mobile application development is simply to create websites for mobile phones. Increasingly this option is becoming more and more viable as more and more can be done from JavaScript in a browser environment. Some of the things now possible with JavaScript include:

• graphics, using the canvas tag;
• obtaining the phone's location on the earth (e.g. from an inbuilt GPS chip), using the Geolocation API;
• limited client-side data storage (the "localStorage" facility)

Native App Development

The other option is to write custom applications (apps) for mobile phones, i.e. standalone, native applications which run independently of a web browser. Such native applications are popularly known as apps. Why might we want to do this? Basically, native apps give you rather more power as a developer to do what you want to do. Some examples:

• We might want to save data in files. A web application only allows limited file storage
• We might want to talk to the mobile phone's hardware, such as its camera or its GPS. While the newer mobile web browsers can do this to some extent, they will not give you the same amount of control over the hardware that a native app will.
• Usability: because development options for native apps are designed specifically for mobile devices, they offer user interface elements geared specifically for mobile users (e.g. touchscreen functionality). By contrast, web development is not aimed specifically at mobile users and a web app may not support the specific forms of user interaction used by mobile users.
• We might want greater control over the visual appearance of the application than is possible with a web application. Standalone applications allow us to be more flexible in drawing graphics, animation, etc. We might even want to develop a 3D application, such as a 3D game. Again, the advent of WebGL (in-browser 3D graphics, supported with Firefox 4 upwards) means that the web option is becoming increasingly viable here.
• We might want a completely off-line application so the user doesn't have to pay for net access, which sadly is still rather expensive, in the UK at least. In this scenario, the user might download data from the web to their phone in advance using their desktop machine; the phone would then work with the pre-downloaded data.

How to develop a mobile application

Typically you download a Software Development Kit to a desktop machine, which comes with an emulator - a graphical representation of a phone which you can test your application on. You develop and debug your code on a desktop machine, and then transfer it to a mobile device, once it's known to work on the emulator. Of course further bugs might come to light on the actual mobile device - probably the trickiest part of mobile development!

Mobile operating systems

Back to the main topic of this week, and what options are available for the development of native (standalone) mobile applications? The first thing to consider is the operating system as different programming languages are supported by different operating systems. The main operating systems are:

• Android (Linux): An open source operating system based on Linux, developed originally by Google and later by the multi company Open Handset Alliance (see Wikipedia article).
• iPhone OS: Apple's operating system, used on the iPhone.
• Windows Phone 7 (or the earlier "Windows Mobile") Windows for smartphones.
• BlackBerry
• Symbian: the operating system used by many non-smartphones. Formerly used on many Nokia smartphones, before they switched to Windows Mobile.

Mobile development technologies

So what are the development options for actually creating applications for mobile devices? The main options include:

• Android SDK
• iPhone, Objective-C
• .NET Framework (Windows Mobile)
• Java ME
• Qt, a cross-platform C++ based development framework available for some mobile operating systems.

Android

One of the leading smartphone operating systems is Android. In the past three years Android has grown from a minority player to one of the leading alternatives to the iPhone amongst touchscreen smartphones. Android is a complete operating system available for mobile devices, based on Linux. Unlike many of the other options, it has been built from the ground up to be open source; the core operating system (except the tablet-only Android 3.0) and many of the standard applications available are open source applications. To develop applications for Android, you use the Android Software Development Kit (SDK) and the Java programming language, but Android has a different runtime environment and GUI system to standard (Sun/Oracle) Java. Consequently, existing Java applications will not run on Android directly, but usually only the GUI need be rewritten.

Advantages of Android:

• Completely open source, so the workings of the operating system are available for anyone to inspect and even change. If the source code is completely open and someone wants to make the phone do something unusual, they can study the workings of the operating system through looking at the source code, and use what they have learnt to develop their code.
• From the phone manufacturer point of view: it is an open specification, so any manufacturer may use it without difficulty; no need for manufacturers to pay for the operating system. Consequently a range of manufacturers including HTC, Motorola and Samsung use Android.
• Uses Java, so easy to develop for if you know Java already.
• Developed by Google, who as the leading net company can put a lot of resources into pushing Android.

Disadvantages:

• Different Android devices support different versions of the operating system, so what works on one Android phone may not work on another.

iPhone

Apple's iPhone is amongst the more advanced smartphones available. It runs its own operating system (iOS) and consequently you need to write applications built specifically for the iPhone. iPhone apps are developed in a language called Objective-C, which is related to C++; like C++, Objective-C adds object orientated capabilities to the older C language. Since it is an Apple product, developing for the iPhone shares similarities to developing desktop applications for the Mac.

Advantages of iPhone development:

• Fast, as it is compiled to the native machine code for the iPhone;
• Applications will run on certain iPods (the iPod touch) as well as the iPhone;
• Quite easy to get publicity for your application, as you offer it or sell it through Apple's App Store.

Disadvantages:

• Not cross platform;
• Objective-C is a fairly unusual programming language;
• The main disadvantage though is how you can distribute your application, which is very restrictive. At the moment, you have to distribute it through Apple's AppStore, and there is the risk that Apple may not accept your application for hosting on the AppStore. This could lead to a lot of wasted development effort!

References:

• Android Documentation
• Wikipedia article

Java ME (Java Micro Edition)

The formerly most widespread development option for mobile devices is probably Java ME (Java Micro Edition), though in the last three years it has been increasingly superseded by the iPhone and Android environments. This is a slimmed down version of the full Java programming language (one of the most commonly used programming languages today) for hardware with relatively limited memory and processing power, such as many mobile phones. BlackBerry uses JavaME plus their own extensions.

• Java is a relatively easy programming language compared to some of the other options, like C++.
• It's easy to get going on Java ME development for phones on Windows and Linux, though a bit more awkward on Mac OS X. All you need to do is download a version of Java (obtainable from java.sun.com) and the Wireless Toolkit (WTK), a development environment for Java ME which comes with a phone simulator (i.e you can see a graphical representation of a phone on your computer, and see what the application will actually look like on a phone).
• Java ME is supported by the majority of older mobile devices (pre-iPhone and Android), particularly Symbian devices such as most Nokias.

So what are the disadvantages?

• Less contemporary phones support Java ME than previously: for example, it is not natively supported on either iPhone or Android.
• Limited in capabilities compared to some of the newer options, for example, saving to and reading from files is tricky as you have to get your app digitally signed by a certification authority to avoid "nag screens" every time the app tries to save to file, and that can be expensive.

.NET Framework for Windows Phone 7/Mobile

Windows Phone 7/Windows Mobile phones do not come with Java ME installed, although you can install Java to them yourself which allows you to write Java applications. However the normal way of writing applications for Windows on a phone is the same as the normal way of writing regular Windows applications: the .NET framework. The .NET framework is a library developed by Microsoft to allow you to create graphical and network applications on Windows operating systems, and you can write .NET applications for it. In terms of the actual programming languages, you would use either Visual Basic or C#.

Advantages of .NET framework:

• Windows developers, with experience in developing desktop applications for the Windows platform, will find it easy to develop new applications, or port existing applications to, Windows Mobile devices.

Disadvantages:

• Windows Phone 7 development has the same issue as iOS development: applications must be distributed via Microsoft's equivalent to the Apple App Store. Earlier versions of Windows Mobile did not have this issue.
• Not cross platform: applications will not run on other mobile operating systems.

So what platform should you develop for?

It really depends upon the features of your application. With native mobile applications ("apps") you have a lot of flexibility compared to the web development (HTML/JavaScript) option, but you need to develop separately for each platform (iPhone, Android, Java ME, etc). So if you are aiming for a cross-platform application which is relatively simple, it's probably best to go for the web option as long as this does not impact negatively on usability. If you wish to take advantage of all the features the phone offers, it's better to go for a native app, but you may need to either pick one platform (and just accept that your app will not work for the others) or develop multiple versions.

Mobile applications and web services

Most mobile apps interact with the web. Mobile apps typically provide location-based information. For example, a mobile app might look up the nearest pubs and restaurants to the user. This would work as follows:

• the app would obtain the location from the phone's GPS device;
• the app would make a connection with the web service using HTTP (all mobile application development environments can connect to a remote server over HTTP);
• the app would send the device's current location over the web to an appropriate web service;
• the service would look up the pubs and restaurants within a certain distance of the user's location and return them to the phone as XML;
• an XML parser within the phone app (most mobile app development environments have a SAX parser) would interpret the data sent back to the browser and incorporate it within the phone's interface.