jackandjill

Android Build Experiments

Bare minimum compile-able and install-able Android Application

Bare minimum android application should consist of a AndroidManifest.xml, may be an Activity or other android component, and may be a launcher for app icon in res.

See directory bare_minimum_android_app for example.

Building APK with Android SDK Command line Tools

Creating apk using command line tools from Android Sdk consists of the below steps. For reference see directory build_with_sdk_tools

1. Generate R.java
2. Compile all java source files (including R.java)
3. Package
4. Sign
5. ZipAlign

• Pre-requisites

1. Following command line instructions has been tested on Windows environment (Windows 10)
2. Assuming you have %ANDROID_HOME% environment variable has been set to Android sdk path which was in my case "C:\Users\m.qasim\AppData\Local\Android\Sdk"
3. Assuming you have buildTools/28.0.x/ is at your %PATH% for easily running appt/dx/jarsigner/zilalign etc.
4. Also obviously, jdk at your %PATH% (i've added the studio embedded jdk to %PATH%)
   To verify environment variables on windows, use echo %PATH% or echo %ANDROID_HOME%

• Generate R.java
R.java contains all the id's generated from resources to be referenced in code. It can be generated using aapt command line tool available in android_sdk/build-tools/28.0.3/appt.

aapt package -f -M ./src/main/AndroidManifest.xml -I "%ANDROID_HOME%/platforms/android-28/android.jar" -S src/main/res -J build/gen -m

• Compile all Java source files (including R.java)
  Since android 8, jack toolchain has been deprecated, we will use javac for compiling source files to classes and then will use dx for dexing.

Since our example has only two source files, i-e MainActivity.java and R.java, we'll compile them both one by one.

javac -d build/classes -bootclasspath %ANDROID_HOME%/platforms/android-28/android.jar src/main/java/io/github/kosmologist/jackandjill/*.java

javac -d build/classes -bootclasspath %ANDROID_HOME%/platforms/android-28/android.jar build/gen/io/github/kosmologist/jackandjill/*.java

Now dexing these class files as Android do not understand java byte directly, instead it uses special bytecode written for android runtime (ART) or previously delvik.

dx --dex --output=classes.dex build/classes

• Package
  Since we have transformed our code into dex format, now it's time to package it with our resources as android application package or apk.

aapt package -f -M src/main/AndroidManifest.xml -I "%ANDROID_HOME%/platforms/android-28/android.jar" -S src/main/res -F build/handlbuilt.apk

Now adding classes.dex file to above created package

aapt add build/handbuilt.apk classes.dex

• Sign
  Since every android app must be signed before running on android (both debug and release) variants, we'll use default debug keystore packaged with android sdk to sign our debug test apk.

jarsigner -verbose -keystore C:/Users/m.qasim/.android/debug.keystore -storepass android -keypass android build/handbuilt.apk androiddebugkey

• ZipAlign
  To compress all resources, we should use tool zipalign as our last step:

zipalign -f 4 build/handbuilt.apk handbuilt-aligned.apk

• Install
  To install the above created apk, we can use adb as following or can be manually transfered to sdcard and install using phone packagemanager.

adb install handbuilt-aligned.apk

References

• https://czak.pl/2016/05/31/handbuilt-android-project.html
• https://czak.pl/2016/01/13/minimal-android-project.html
• http://tools.android.com/tech-docs/jackandjill#TOC-Compilation-support
• https://github.com/czak/minimal-android-project
• https://medium.com/authmane512/how-to-build-an-apk-from-command-line-without-ide-7260e1e22676

Building with Gradle without Wrapper

Without wrapper it's very easy to build apk, we just have to include a build.gradle in the root of project with contents as shown in build_with_gradle_without_wrapper directory.

To Build, just use gradle assembleDebug assuming, gradle is installed and is at %PATH%.
To install gradle, just download it as binary and add the bin directory to %PATH%, or use scoop.sh. (gradle -v)
Note: example above is built using gradle v5.4.1 and android plugin for gradle v3.4.0.

References

• https://scoop.sh/
• https://developer.android.com/studio/releases/#aapt2_gmaven