Archived:Porting from Android to Nokia Platforms
Porting Android apps to Nokia Platforms
Android applications are typically written in the Java™ language. Despite the machine-independent Java language, however, the applications are Android-specific and are heavily based on the Android Application Framework.
As a result, direct code-level reuse is typically not possible in porting of the applications. In most typical cases, it is recommended that you reuse the application design and graphics and rewrite the code using Qt technologies, but there are also several special cases.
The following article describes recommended ways to port different types of Android applications to Nokia platforms, and also covers the most typical special cases.
Overview to Porting from Android
The Java code written for Android's Application Framework is not compatible with, for example, Java MIDP (Java™ Platform, Micro Edition [Java™ ME]) libraries traditionally used in mobile devices.
In some specific cases where there is a relatively great amount of Java-based application logic and a very simple UI, the best option to port the application may be to use the mobile information device profile (MIDP), which allows code-level reuse. MIDP MIDlets can be run on Series 40 and Symbian devices from Nokia, but not on Maemo™ devices.
In general, the recommended way to port is to rewrite the application with Qt to enable the best possible experience on the latest Symbian and Maemo devices, as well as future-proof implementation.
Android runs the Linux kernel underneath, in a manner similar to Nokia’s Maemo platform.
Unlike Maemo, however, Android has very different application level layers on top of Linux. Direct porting of applications by reusing code between these platforms is typically not possible, despite the underlying Linux platform.
While Android development is based on its Java-based application framework, Maemo applications are built using tools and technologies that are commonly known in the Linux world, such as GTK, SDL, and nowadays the Qt cross-platform application framework, which also supports Symbian devices.
Java Native Interface
A notable special case of the above is where the Java Native Interface (JNI) is used in the Android application. JNI allows the use of C/C++ shared libraries from Android code.
Although this is not a recommended way to develop basic Android applications, it is very useful in some specific cases — for example, with games relying on existing game engines, which are often written in C/C++.
If the Android application uses these kinds of C/C++ shared libraries, code-level reuse is also often possible, especially towards the Maemo platform but also sometimes towards the Symbian platform.
Nowadays, in addition to developing Android applications directly in the Java language, several Android applications are also built as web applications using the WebKit approach with tools like Titanium Mobile or by utilizing the LibWebCore in manual fashion from the Android application.
These types of web applications are usually best to port to Nokia platforms using Web Runtime (WRT) technology; Porting iPhone web app to WRT on Nokia devices. A Qt WebKit approach or simply rewriting the application with Qt Quick are also options to consider, especially if the intention is to develop an impressive UI. For more information on Qt Quick, see Porting Mobile Applications to Qt: Qt Quick.
Developers could also consider building a native Qt application and basing its functionality on embedded web views; for more information, see Porting Mobile Applications to Qt: Web View in iPhone, Android and Qt.
Although code cannot typically be reused, the graphics and design of the application can often be reused to good effect. For example, in Qt Quick, scaling of the existing UI elements is very easy and may not require much rework from the UI designers. Generally, however, your application will look best and be most usable if you take some time to redesign the application layout. An application layout that looks great on an Android device may not be very usable on a Nokia device, since the usage paradigm of user interface and available features affecting the user experience are different. For more information on UI design for Nokia devices, see the Forum Nokia Design and User Experience Guide.
How to Proceed with Porting
To proceed with porting, the following guides are recommended (part of this "Porting mobile application to Qt" article series):
- Porting Mobile Applications to Qt, if your existing application is UI intensive, or for any generic native iPhone application. This is the main introductory article about porting to Qt.
- Porting from iPhone to Nokia Platforms - high-level starting guide for porting iPhone applications to Qt
- Fundamental use cases for porting iPhone and Android applications to Qt - a few powerful modules and how to port those to Qt
- Useful-porting-examples - common features needed for porting applications to Qt
- Qt Quick examples for porting - examples for creating fancy UI elements with Qt Quick
- Wordpress developer story describes the real-life experience of porting an application from iPhone to Qt. Both iPhone and Qt sources of the Wordpress client are also available as open source.
- See also Forum Nokia Design and User Experience Guide for ideas on how to achieve the best possible user experience when porting your application for Nokia devices.
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