Friday, May 15, 2009
My name's Jon Evans. I'm a novelist, journalist, comics scriptwriter, and lapsed former software engineer - see my web site rezendi.com for far more than you ever wanted to know. This is a blog about my (mis)adventures in Android development, and related subjects.
I used to be a fairly expert software developer, with an EE degree from Canada's University of Waterloo, and years spent as a coder and project lead at various consulting companies in California, London, New York, and Toronto. Then I took six years off to write books. Now that I'm jumping back in the saddle (currently for fun, eventually for profit) I thought that documenting what I learn en route might be useful to both myself and others.
So, let's begin at
You need to download three things to start working with Android: the latest Java Software Development Kit (SDK) the Eclipse Integrated Development Environment (IDE), and the Android SDK itself. Technically, you could live without the Eclipse IDE, but trust me, it makes your life a lot easier.
The downloads were pretty straightfoward. Unpacking the zip files took forever, as in several hours. I suppose this is what I get for having Windows Vista on my development machine. It has already become apparent that I need a faster computer; my two-year-old cheapest-Dell-that-money-could-buy is still perfectly adequate for word processing and web surfing, but software development is a little more demanding.
The Android SDK comes with decent getting-started documentation, including a detailed "Hello world!" howto. A longstanding software tradition dictates that the first thing one does with any new development platform is make it output "Hello, world!" to your screen; and a longstanding truism warns that if this is hard to do, it means your new platform is complex and difficult to work with.
Fortunately, Android was pretty straightforward, at least in Eclipse, though I suspect without the IDE I would have been muttering and cursing in fairly short order. First you have to create the "virtual device" on which your code will run; basically, a software emulator of an Android phone. Then you create an Eclipse project, and four files: HelloWorld.java (five lines of code), AndroidManifest.xml (packaging information), main.xml (UI information) and strings.xml (what it says on the box.) When you run them, a very impressive emulated Android phone pops up on your screen, and when you push its MENU button to unlock it, voila, "Hello, Android."
Two notes. One is an Eclipse bug; it sometimes hangs when launching the emulator, without ever installing your package and/or turning over control of the virtual phone. This seems to be correlated with adding or removing Eclipse projects beforehand. (Note, however, that you can and should re-install packages into a running emulator.)
The other is that I had to go into the filesystem and remove a bunch of source files that began with "._" for the app to work. This was true for the Notepad tutorial files as well.
Oh, yes. The tutorial. "Hello world!" is useful, but doesn't actually teach you all that much, especially in an environment where (so far, at least) you mostly write connective tissue for Android's extensive existing capabilities, rather than creating things from scratch. So the SDK comes with a three-step Notepad tutorial to introduce you to its class hierarchy, application lifecycle, and object library. I was impressed by how much you can do with just a few lines of code.
Like all good software engineers, I intend to do Test-Driven Development. (Well, sorta. Full-on TDD means you write the tests first, then the code; I'm going to cheat a little and do "code a little, test a little, code a little, test a little" instead.) In theory, Android comes with built-in out-of-the-box unit-test capabilities that makes this very straightforward.
The practice is a little more challenging. Not least because the "API Demos" part of the SDK failed to install on my machine - the documentation wasn't created, and the classes won't compile, for no obvious reason. The source code remains accessible, but there's still no succinct explanation of how to create Android test cases, much less a full-fledged Android test harness.
So I spent an hour or two today trial-and-erroring my way through that obstacle course, and am pleased to say that I now have Android unit tests working both from within Eclipse and from the command line. I was helped greatly by this blog post and those it links to. Here's my own attempt to summarize:
- Create an Eclipse project with your working code. (In my case, the project is WTW, and the java package is "com.rezendi.wtw").
- Create an Eclipse project where test code will go. (In my case, WTWTest, java package "com.rezendi.wtw.test").
- Write a test case that inherits from android.test.AndroidTestCase, and create "testXYZ()" methods in it. (I haven't yet written tests that use the emulated phone's Context; that's the next step. But I presume since basic tests work on the emulated phone, the more complex ones will too.)
- Modify the AndroidManifest.xml in the test project to point to an InstrumentationTestRunner. Something like:
<?xml version="1.0" encoding="utf-8"?>
android:targetpackage="com.rezendi.wtw" android:label="Tests for WTW.">
- To run it from Eclipse, right-click on (I think) either WTW or WTWTest, and select "Run As -> Android JUnit Test." The emulator will launch. Once it has, select the phone's app list (that upward-arrow button from the home menu), select "Dev Tools", select "Instrumentation", and then select your package (in this case, "WTW".) JUnit output should go to your Eclipse console.
- If you find this ridiculously complex and time-consuming - and you should, because forcing the user to jump through all those UI hoops to run tests that should be automatable is ridiculous - you can do the same thing through the command line. Run your test package normally, ie as an Android Application. Ignore the "no Launcher activity found" warning. The package being tested will also be installed into the emulator.
- Once the emulator is up and running, open a command line, go to the "tools" subdirectory in your Android install directory, and use the "adb" tool to connect to the emulation and run your test cases. In my case, the correct command line is: "adb shell am instrument -w com.rezendi.wtw.test/android.test.InstrumentationTestRunner".
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