Repackage APK file to contain custom assets - what build tool to use?

Question

Update: This is an old post, and references below to broken aapt versions will be out of date.

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Based on previous feedback, I am storing custom text fields in the assets directory of my app.

I will write the app, using default user details in an asset file, and the client would like to rebuild the app for each user, including that user's details in the asset file.

(I am aware this is method has some serious shortcomings, but the client is still keen to do it in this way - see Embed login details in APK file, different for each user (or other options?))

This question relates to troubles I am having with rebuilding the APK file, once I have unzipped it, and updated the custom asset file. I am quite convinced I am missing something small, however, the documentation and posts I have found on these methods are not helpful enough for a newcomer.

1. aapt - Android sdk tool: Unfortunately the android docs on "Using aapt" on the android docs [link 2 below] are very limited. The console command -help shows a bit more info. When trying to use it to just add a file to the test.apk, it ends up deleting the original, and creating a new file test.apk.zip containing only the file I tried to add. I have not been able to find the correct command line combination to take an unzipped apk and repackage it - that would be my first prize.

2. apkbuilder - Android sdk tool: Firstly this tool is deprecated, which is a negative point for it. I also can't get it to work with what I have in that unzipped folder. I think I'm missing a pre-apkbuilder step because apkbuilder asks for a resource zip archive, and I have a resource folder.

3. ant - build tool: Other similar posts say to build with ant, rather than using the android tools. I am having trouble getting ant to work. One particular link to Getting Ant to Work with Android [link 3 below] looks promising but looks like it is for a different android sdk (my build.xml that is generated by android looks different to his). Unfortunately I know little about ant, and am having trouble becoming expert enough to solve my current issue.
   Further to NickT's solution below - running the ant script gives me the error
   taskdef class com.android.ant.SetupTask cannot be found using the classloader AntClassLoader[].
   I have found some references online to this error, have confirmed that local.properties has an sdk.dir setting that is pointing to my android sdk install folder (sdk.dir=/Applications/android-sdk-mac_86).

4. ?????: There might be some other option that I have not listed / discovered, which I would be interested in hearing about.

I realize that delving into the gears that are normally covered up by my ide can lead to diffuculties. But I know that a lot of the SO users can do many of these things, and I hope I get the interest of some of them. Thanks for any help.

(Eclipse 3.6 on Mac Snow Leopard 10.6 64 bit)

PS, I am not able to post more than 1 hyperlink yet, so I have included these addresses to show more info to my question.

(1): https://mcmap.net/q/1163602/-embed-login-details-in-apk-file-different-for-each-user-or-other-options

(2): developer.android.com/guide/developing/tools/aapt.html

(3): www.disgruntledrats.com/?p=27

Antonomasia

See this: #4192262 – Chipper

Answer 1

To answer my own question with the method we finally chose, and "for the record":

I was unable to get Ant working correctly for me (my lack of understanding).

I ended up using the aapt tool. It works as per the Android sdk documentation and really is quite simple to use:

aapt add -v Test.apk "assets/readme.txt"

This will add a readme.txt file (we were storing it in a subfolder of the current running folder, called assets. If you want to store the new file somewhere else, aapt does offer a command line switch to specify that)

However, there are some caveats:

1. I couldn't get it to work on signed APK files.
2. some versions of aapt don't work properly! They don't recognise the subfolder...

To solve 1:

1. Export the APK from eclipse as an unsigned APK.
2. Use the keytool to generate a key (see Android dev docs).
3. Use aapt.
4. Sign the APK using jarsigner.

To solve 2:

I can't really help with this. Every version of the SDK (on Mac) I tried to download included an aapt tool that did not recognize the subfolders. A colleague downloaded a version that worked, but we could still not figure out which version it was that he downloaded, so we kept this "magic" copy and renamed it and will be using it until we find a new version that works.

Antonomasia

Can you explain stages 2 and 4 more in the first solution? – Callery

Thanks so much for this answer. Just what I was looking for. No problems with 1 or 2 yet since I'm not signing my apks yet but wanted to dynamically change data and this does it perfectly. – Rasure

Thanks for your post. It leed me to my solution. For automatation see my post – Osteo

You can call 'unzip app.apk -d ./app' followed by 'rm -rf ./app/META-INF'. Then zip the file back up and rename it to .apk and this will give you an unsigned version of the same apk file. – Lignify

Answer 2

The simplest solution would be to give the template source of the app to your client with a script that rebuild the app from scratch.

This way your client simply have to change the assets in the folder, double click a batch file and get the apk in a minute or so.

You don't have to know anything about ANT to compile and package without the IDE, just follow the steps here :

http://developer.android.com/guide/developing/other-ide.html

The ANT script is generated by the "android create" "android update" commands. You then just need to run "ant release" and off you go.

Hardworking

Thanks, Yahel, unfortunately I had read that link already, and still the ant does not build. More details below with Nick T's solution. – Antonomasia

Answer 3

A bit late, probably, but this post appears in lots of searches, so I thought this may be of interest.

I just used a standard Zip tool to 'unsign' the APK by removing the META-INF folder, updated any asset files, and then resigned the APK using jarsigner. (If I could find a way to sign JARs without using jarsigner, so we wouldn't need the Java SDK installed everywhere, this would be really useful - ideas anyone?)

Potentiate

Answer 4

To expand on Yahel's answer, yes I think Ant is the way to go. It can be a bit intimidating, but it's urprising how well it works 'out of the box' without too much messing about. Customising it takes a bit of reading but I managed it, so I'll give you the benefit of my experience.

Firstly create a sample application as suggested. Let's suppose you want it to be created in c:\junk. Then from your a command prompt in Android SDK\tools directory type:

android create project -t 5 -n AndSampleApp -p c:\junk\AndSampleApp -a AndSampleApp -k com.yourpackage.andsample.

( -t 5 gives you API level 7, type 'android list targets' to see other options)

Let's assume you've been building your projects in an Eclipse workspace (it's /dev/projects/EclipseHelios/AndroidWorkspace on my machine). Copy the sample app's build.xml and build.properties to the project folder in Eclipse

and edit the newly created build.xml and remove the line

<project name="AndSampleApp" default="help">

and replace it with just:

<project>

Now edit the the newly created build.properties which will be empty except for comments and add (customisng where necessary):

# The password will be asked during the build when you use the 'release' target.
# OH NO IT WON'T! IF YOU PUT THE KEYS & PWDS IN AS BELOW - It'S AUTOMATIC

# Customised (hard coded) section ---------------------

projectname=YourActualProjectName

# Line below is the parent folder of where the sources are
workspace.dir=/dev/projects/EclipseHelios/AndroidWorkspace

# Line below is where you want the binaries to go
outbasebase.dir=/dev/projects/AntBuilds

key.store=c:/users/you/your-release-key.keystore
key.alias=your_release_alias
key.store.password=YourSecretPassword
key.alias.password=YourSecretPassword
#------------------------------------------------------

ant.project.name=${projectname}
base.dir=${workspace.dir}/${projectname}
source.dir=${base.dir}/src
outbase.dir=${outbasebase.dir}/${projectname}
out.dir=${outbase.dir}/bin
layout.dir=${base.dir}/res/layout

If you then get a command line prompt in /dev/projects/EclipseHelios/AndroidWorkspace/YourActualProjectName

and type 'ant release', you should end up with a built and signed apk in /dev/projects/AntBuilds/YourActualProjectName

You should be able to customise the assets location by the adding an assets.dir entry in the build.properties

Idaline

Thanks, Nick, I am still getting the error: "taskdef class com.android.ant.SetupTask cannot be found using the classloader AntClassLoader[]" - have updated original post with this info. – Antonomasia

Take a look here, it seems the properties do not accept non ascii characters : blog.klacansky.com/matter-code/… – Hardworking

Thanks, Yahel, I found that link - I don't think I'm breaking any non ascii rules with "/Applications/android-sdk-mac_86". I will add to these answers later today with info on how I got aapt to work. – Antonomasia