Programming for Android
So I’ve done my first programming for Android phones and thought I’d write a blog post about the experience.
Programming for Android is a bit different from working with the Compact Framework. The abstraction level for the Dalvik applications is somehow high than the Compact Framework application. One difference for example is that there is no main() method to start your application from.
Central for an Android application is its Android Manifest file. This file describes all services and activities available in the application. This is an XML file that helps describe your application to Android, what it’s capabilities are. Each Activity can then be used as an Entry point, but the manifest also describes Services, Content Providers and Broadcast receivers.
What this gives you is a set of loosely coupled components that interact with each other using Intents, that are passed on a system wide message bus. This allows applications interact not only with central parts of the phone, but also with other applications. Which is quite interesting.
Developing in this manner gives you a set of conventions to follow. I feel that they have managed to find a set of conventions that gives direction in the design of the application, but doesn’t confine you.
The SDK also gives you a set of base classes (template method pattern style base classes) that helps you develop common tasks in a standardized way. An example of these are the Task classes that provide threading and scheduling support. I quickly fell in love the the AsyncTask for example.
Android protects the foreground UI thread quite extensively, making these constructs for doing background work important. For example your not allowed to construct or access any UI elements on background threads. This can be handled by using a special Looper construct that effectively divides your Thread code into different parts. One setup part that’s allowed to access, or setup UI components. And one Loop part that does the actual work.
I worked mainly in the Emulator. The emulator feels fast at first, it takes a while to boot up but is quite responsive once booted. That is until you start typing using the computers keyboard. When you do this the emulator feels slow. Apart from a few issues with the emulator loosing “internet connectivity” when my computer Hibernated.
Now it’s time to mention a tool that’s quite helpful when working with Android applications. It’s the adb.exe logcat tool available in the Android SDK. This tool allows you to watch the result of log statements in runtime, and shows stack traces for those errors the occur but you’ve partially managed to take care of (ignored).
This being said there are some things I’m missing when comparing to working with the Compact Framework. For example, working with XML is much easier in the Compact Framework. I hate having to write my own parsing and serialization code, and there are more tools to help me generate code for doing this in the .Net framework.
Also using the HttpClient in the Android SDK is unnecessarily hard. Https works only with some special glue code. And as far as I can tell everyone seems to simply accept any certificate instead of providing support for showing a UI where the user can accept an unknown (self-signed) certificate.
This is all I can think of right now (this is the second time of writing since I had a crash when I tried to post it…). If there are any questions, please ask them. Hopefully they’ll help generate more knowledge about Android development.