Command-line builds for Android using ant (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Thu, 28 May 2015

Command-line builds for Android using ant

I recently needed to update an old Android app that I hadn't touched in years. My Eclipse setup is way out of date, and I've been hearing about more and more projects switching to using command-line builds. I wanted to ditch my fiddly, difficult to install Eclipse setup and switch to something easier to use.

Some of the big open-source packages, like OsmAnd, have switched to gradle for their Java builds. So I tried to install gradle -- and on Debian, apt-get install gradle wanted to pull in a total of 153 packages! Maybe gradle wasn't the best option to pursue.

But there's another option for command-line android builds: ant. When I tried apt-get install ant, since I already have Java installed (I think the relevant package is openjdk-7-jdk), it installed without needing a single additional package. For a small program, that's clearly a better way to go!

Then I needed to create a build directory and move my project into it. That turned out to be fairly easy, too -- certainly compared to the hours it spent setting up an Eclipse environment. Here's how to set up your ant Android build:

First install the Android "Stand-alone SDK Tools" from Installing the Android SDK. This requires a fair amount of clicking around, accepting licenses, and waiting for a long download.

Now install an SDK or two. Use android sdk to install new SDK versions, and android list targets to see what versions you have installed.

Create a new directory for your project, cd into it, and then:

android create project --name YourProject --path . --target android-19 --package tld.yourdomain.YourProject --activity YourProject
Adjust the Android target for the version you want to use.

When this is done, type ant with no arguments to make sure the directory structure was created properly. If it doesn't print errors, that's a good sign.

Check that local.properties has sdk.dir set correctly. It should have picked that up from your environment.

There will be a stub source file in src/tld/yourdomain/YourProject.java. Edit it as needed, or, if you're transferring a project from another build system such as eclipse, copy the existing .java files to that directory.

If you have custom icons for your project, or other resources like layout or menu files, put them in the appropriate directories under res. The directory structure is the same as in eclipse, but unlike an eclipse build, you can edit the files at any time without the build mysteriously breaking.

Signing your app

Now you'll need a key to sign your app. Eclipse generates a debugging key automatically, but ant doesn't. It's better to use a real key anyway, since debugging keys expire and need to be regenerated periodically.

If you don't already have a key, generate one with:

keytool -genkey -v -keystore my-key.keystore -alias mykey -keyalg RSA -sigalg SHA1withRSA -keysize 2048 -validity 10000
It will ask you for a password; be sure to use one you won't forget (or record it somewhere). You can use any filename you want instead of my-key.keystore, and any alias you want instead of mykey.

Now create a file called ant.properties containing these two lines:

key.store=/path/to/my-key.keystore
key.alias=mykey
Some tutorials tell you to put this in build.properties, but that's outdated and no longer works.

If you forget your key alias, you can find out with this command and the password:

keytool -list -keystore /path/to/my-key.keystore

Optionally, you can also include your key's password:

key.store.password=xxxx
key.alias.password=xxxx
If you don't, you'll be prompted twice for the password (which echoes on the terminal, so be aware of that if anyone is bored enough to watch over your shoulder as you build packages. I guess build-signing keys aren't considered particularly high security). Of course, you should make sure not to include both the private keystore file and the password in any public code repository.

Building

Finally, you're ready to build!

ant release

If you get an error like:

AndroidManifest.xml:6: error: Error: No resource found that matches the given name (at 'icon' with value '@drawable/ic_launcher').
it's because older eclipse builds wanted icons named icon.png, while ant wants them named ic_launcher.png. You can fix this either by renaming your icons to res/drawable-hdpi/ic_launcher.png (and the same for res/drawable-lpdi and -mdpi), or by removing everything under bin (rm -rf bin/*) and then editing AndroidManifest.xml. If you don't clear bin before rebuilding, bin/AndroidManifest.xml will take precendence over the AndroidManifest.xml in the root, so you might have to edit both files.

After ant release, your binary will be in bin/YourProject-release.apk. If you have an adb connection, you can (re)install it with: adb install -r bin/YourProject-release.apk

Done! So much easier than eclipse, and you can use any editor you want, and check your files into any version control system.

That just leaves the coding part. If only Java development were as easy as Python or C ...

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[ 20:52 May 28, 2015    More programming | permalink to this entry | comments ]
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