You’ve read the startup docs and completed your first tutorial, and now you’re ready to start creating that killer app that’s been consuming you for all this time. Diligently you start a new Android project in eclipse, open your main Activity and then…
Well what now? It’s not too long before you’re off trying something that wasn’t covered in those Hello World tutorials and suddenly you’re going off-road and can’t find yourself on the map. Soon the trail ends with you spinning your wheels, momentum gone.
While there are many articles out there that promise to “get you started” with Android, its hard to find any that keep you going once you’re on your way. So I thought I’d share some resources that can be used to break through those beginner hurdles or provide a compass when you find yourself in unfamiliar territory.
Diggin The Docs
The Android documentation itself has improved tremendously since I first started working with the 1.0 SDK. You’ll find there’s really a wealth of information once you start doing some digging. Some of these are obvious, but beginners tend to fly right by them, so I’ll just draw your attention to them.
The Topics area is a nicely curated list of material from the articles, samples and tutorials, grouped by, well, topic.
One of the areas you are likely to first get hung up on is using layouts. Look at the User Interface topic for some good articles, it also usually contains the content from the Layout/Views topic as well.
The New Features topic is always worth checking out, expect new articles a few days to weeks after a new sdk version is released.
With 30 or so articles, its likely there’s one that touches the area you’re working in. Even if its not exactly what you’re looking for, there’s usually a tip or two that you can pick up and use. The series of Layout Tricks articles and the one on Painless Threading are good reads.
The sample apps can be used as a starting point for your own app, or just used to study some techniques. Each sdk release brings a few new sample applications that are always worth investigating. Nothing’s been bigger than the new Honeycomb release for tablets, and the Honeycomb Gallery and Renderscript samples give a good look at some of the new features.
But the sample I’ve found to be the most useful is the Api Demos. Its been there since early versions of the sdk, and I still find myself turning to it when I’m first working in a new area. Its a single application that contains many small sample apps, covering virtually all aspects of the basic platform.
When you start the application you’ll see a list of different categories or platform features.
Usually there will be sub categories within each selection and then finally one or more sample apps that demonstrate different aspects of a feature. It’s not always totally intuitive what will be in each category. I’d recommend just flipping though them all to begin with. The Api Demos page in the documentation also is laid out the same as the application, so you can navigate through the docs to also see what’s available. However, I think its better to do it within the application itself, because you will be able to see the samples in action, making it easier to grok what they are trying to demonstrate.
This section provides quick examples that can be used when first familiarizing yourself with a feature.
It may seem simple, but understanding an Android project’s file structure is always helpful.
The section on Opening a new screen provides some great fundamental knowledge, whereas Referring to localhost demonstrates a very specific task you may require when running an emulator .
I’ve noticed though that old articles are not necessarily kept up to date with changes to the api or best practices, nor are they pruned from the documentation. For example, the section on Threading doesn’t refer to the more recent AsyncTask, which is the preferred method that is explained in the Painless Threading article.
Treat all these resources as a source of knowledge, not necessarily the source of truth.
Android Reference docs (javadocs)
Much closer to the source of truth are the reference docs themselves. I may slip and refer to them as javadocs, because that’s basically what they are. They are generated by the class and method javadoc comments found within the source files. And because the documentation is included in the class itself, there’s a better chance that when the class is changed, the documentation will be updated as well.
It turns out that for many of the important fundamental classes in the sdk, there is some great class level documentation that provides detailed explanations one use of the class.
Along with the AsyncTask I just referred to, a few of exceptional note are the docs on the Activity and View classes.
Besides just the information on using the specific class, each really becomes a technical article itself. The Activity class doc provides a great primer on the activity life cycle (right), how persistent state is saved, how to start activities, working with permissions, configuration changes and more.
The View class doc describes how common properties are used, how to create a custom view, how views are used in layouts, details on how the system measures and draws views, the basic event handling and threading of views and more.
Beyond the class documentation, some of the package level documentation does better than simply listing the classes and interfaces contained within it. The android.app package documentation provides a brief summary of the important classes as well as links to other sdk documentation where you can find more in-depth information. The new android.renderscript documentation includes a useful overview of this important new Honeycomb feature.
I think one of the bigger challenges is coaxing android into rendering the UI of your app as you’ve designed it. I’m always opening the reference docs to understand the properties available to the layouts and views. Each View or Layout class will include a section that describes the xml properties that are supported and how they are used. Its important to remember that these properties can also be inherited by the parent classes, so make sure to always check what’s available from the super classes.
Of course the source of truth is the android source code itself. If you get into creating custom views, adapters or the like, its helpful to see the code of the parent class to understand exactly how to extend its base behavior. Even if you aren’t doing anything that complicated, you’ll probably find yourself at some point running the debugger on your code, tracking down some mysterious issue, and discover the trail runs cold as the debugger steps into the framework classes. It would sure be nice to step into that actual code, where the core of your issue could be revealed.
Turns out it’s not too hard to get the android source exposed in your debugging session thanks to a generous guy who created the Android Sources eclipse plugin for just this use case! Install the plugin by adding the update site into eclipse, and all your projects will automatically have the android source, specific to your targeted api level, available when debugging.
If you’d like a little more direct access to the code, you can browse the repository from the web. However, it’s not as simple as you might think. The Android platform is actually spread across many different repositories, and trying to figure out how to find the class you’re look for can be challenging. Fortunately, 90% of the code you care about is found in the platform/frameworks/base project.
Of course you’ll quickly find that any in-depth investigation of the source using this method is less than ideal. Eventually you’ll just want to have the source locally, maybe even as an eclipse project, so you can easily navigate the code. Roll up your sleeves, this takes a bit of work.
First, know that Android is managed using Git and as said before, is spread across many, many repos. But we only need to get the source from the platform/frameworks/base.git repo. Android provides some instructions on working with source, but that’s geared towards users who are going to be contributing to the platform, and so is more complex than you’ll need.
Explaining how to use Git is beyond this article, but in short, you first clone the remote repo, which creates the complete repository on your local machine. Then you checkout a specific branch from your local repo, corresponding to the api level you are targeting. Now you will have the source code in a local workspace. It’s going to look something like this…
git clone git://android.git.kernel.org/platform/frameworks/base.git android-src cd android-src git checkout -b gingerbread remotes/origin/gingerbread
Finally, create a new project in eclipse, choose to base the project on existing source, and point it to your android source directory.
Thinking Outside the Docs
Of course there are plenty of other great resources you can use besides the official Android documentation.
Since the beginning, Android has used Google Groups as the primary forum for discussions with the developer community. There used to be 2 main groups, android-beginners and android-developers. Today, only the android-developers group is still active, but it’s a great place to ask questions. There are several developers from the core framework team who will occasionally join in the discussions. Of course, many developers have already probably asked a question similar to yours, so first make sure to search the forum and read all similar discussions. I’ve found my questions are usually already answered, or I get enough information to figure it out myself. Plus, you’ll find many of the early posts had much more participation from the framework developers, so you can gain a lot of insight from those older threads.
So what happened to the android-beginners forum? Well, they dropped it in favor of the new default forum of all developers, stackoverflow.com.
So much of the discussion had started moving to Stack Overflow that android finally just formally told everyone to go there with the basic android questions. In order to effectively search the android discussions, use the tag “[android]” in your search. You can view all the latest android discussions at http://stackoverflow.com/questions/tagged/android.
The web is full tutorials on various aspects of android, and listing them all here is impossible, so here are a couple that I’ve found helpful.
These guys have put together an impressive 8 part tutorial that builds a full application using the common features many applications will need.
- Part 1: Main Activity UI
- Part 2: Using the HTTP API
- Part 3: Parsing the XML response
- Part 4: Performing the API request asynchronously from the main activity
- Part 5: Launching new activities with intents
- Part 6: Customized list view for data presentation
- Part 7: Using options menus and customized dialogs for user interaction
- Part 8: Creating an AppWidget for the home screen
Germany’s prolific Eclipse and Java blogger/trainer has put together several good Android tutorials that cover the basics of many features. One thing I really like about his tutorials is that he updates them when new apis are released and also fixes bugs that others point out. And he lists the revision history at the beginning of the article, so you know how current the information is. The tutorial on using the ListView/ListActivity is recommended.
Open Source Apps
Tutorials and samples are great, but nothing beats studying a complete published application. How about one with over a million installs? How about the Foursquare app?
Yep, that’s right, the Foursquare app, foursquared, until a short time ago, was open source. Seems like they took it private in the beginning of the year, but you can still get the code up to that point, and it provides some great examples for UI, notifications, connecting to twitter, working with maps, and, of course, location!
Its hosted on Google Code using Mercurial, which many people aren’t familiar with. If you have used Git (maybe to pull the Android source?), then it’s easy. Simply download and install the Mercurial client to your computer and clone the repo like you would with Git.
hg clone https://foursquared.googlecode.com/hg/ foursquared
This creates a local copy of the repository in the directory
foursquared. Then you can create a new Android project in Eclipse based on the
/main directory. In order to properly build the code and run it in an emulator, there a few configuration steps required. These have been documented in the
The WordPress for Android app is no slouch, with several hundred thousand installs, plus the project is still open and very active. Looking for an example of XML-RPC over SSL? Here you go! This time you’ll need to use Subversion to work with the source.
Aside from the samples in the sdk, Google has also shared some further apps-for-android, containing several 2d gaming apps, use of the accelerometer, a mashup with YouTube, and others.
Looking for more? Doesn’t wikipedia know everything?
One of the great things about working with Android is the community around it. People are always the best resource to keep you moving and motivated. And where I go to find this community is Twitter. There’s plenty of Android activity on Twitter, people sharing the latest news, tips, advice and links to great content.
You may want to follow this list of Android developers and enthusiasts that I’m curating. And of course you can also follow me!
This is by no means a comprehensive look at all the Android resources out there – that’s what Google is for! However, I hope it provides a useful guide that can keep you from getting stuck, stay moving, and give you the occasional boost needed to complete that app.