Develop Reference

How can I get rid of unnecessary code in .apk file?

I have an empty project (no classes whatsoever, no activities), only a dependency to com.google.android.material:material:1.3.0 for the code to compile (there is a style defined which uses this).
I enabled shrinking option, yet, after generating the signes APK, there is a classes.dex file in the apk with a shitload of code, even though the app has no code. Why and how to I get rid of those, to make sure the apk contains only what is needed, no extra bloatware? Thank you.
This is the expanded apk:

For code shrinking please turn on Proguard and you have the option to customized Proguard rules as you need.
buildTypes {
release {
shrinkResources true
minifyEnabled true
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
debug {
}
}

TRY 1
Open .jar file (appodeal.jar) and remove all .dex files.
TRY 2
Use the built-in inspection Java | Declaration redundancy | Unused declaration.
To run it on whole project go to Analyze -> Run inspection by name..., type Unused declaration and select desired scope. Then carefully check output and mark some classes as entry points if needed.
Select Unused declaration node in list and perform Safe delete action on all unused declarations at once.

Exclude xml files from compilation android [resource shrinking]

I would like to use some xml files as mockups to preview different states of a layout, but I don't want to include it in the apk because thes xml files are only dedicated to preview purposes. I would like to tell gradle which files/directories to ignore for resources.
It would also be useful to easily reduce apk size for low memory devices by using products flavors, in a similar way as this excellent article explains.
Maybe proguard could help?

If you are using the android studio you can add resources by build flavors your want example you can add string resource for debug build only and different string resource for main release build. You just right click add a xml resource choose a resource type and specify the source set.
if you add a layout for debug flavor only and not in main release then everytime you sign an apk the those layout will not be included in apk. Hope it helps :)

We call it "Resource shrinking". All info about it is here.
Look at shrinkResources true. Build system will try to find unused resources files with this flag, and will remove them from the build. You can add it to your debug buildType, and on any build flavor.
android {
...
buildTypes {
release {
minifyEnabled true
shrinkResources true
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}

How to make Proguard obfuscate using Android Studio

ProGuard is not doing a very complete job of obfuscating my Android project. When I decompile my apk at decompileandroid.com I see that it is only changing the name of local temporary variables and nothing else. It is not changing class names, variable names, method names, or anything else.
After reading the manual all of the optional commands seem to be telling it NOT to do something so I am left to think it should obfuscate everything by default.
my build.gradle has the following...
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
}
}
Neither of those two files exist is the project. The project is as it was converted from Eclipse by Android Studio.
What am I missing. Do I need to create those two files and put some proguard parameters in them - if so what. I want maximum obfuscation.
Thanks,
Dean

Set minifyEnabled true in order to turn on code shrinking, and
then shrinkResources true to turn on resource shrinking.
Reference for the quote

How to reduce and compress an apk file in android

I have one apk file but its file size is 22.4 MB. It's huge, so I need to reduce or compress the apk file in android. What is the right way to reduce and compress the apk file size?

You can compress an APK file (rar, zip), but it has to be decompressed in order to work.
If the apk file to large to distribute you can:
Use expansion files: http://developer.android.com/google/play/expansion-files.html
Create multiple versions of your apk: http://developer.android.com/google/play/publishing/multiple-apks.html (e.g. no hdpi files for ldpi devices)
Use ProGuard
ProGuard is a free Java class file shrinker, optimizer, obfuscator,
and preverifier. It detects and removes unused classes, fields,
methods, and attributes. It optimizes bytecode and removes unused
instructions. It renames the remaining classes, fields, and methods
using short meaningless names. Finally, it preverifies the processed
code for Java 6 or higher, or for Java Micro Edition.
If you use Eclipse, A default configuration file will automatically be added to your Project. But this default configuration only covers general cases, so you most likely have to edit it for your own needs.
Remove unused resources: https://code.google.com/p/android-unused-resources/
Optimize your images by using tools like 9patch and png optimizers
Remove everything that is only used for debugging purposes (debug classes, or even Log() methods). Also try removing unnecessary .so files

You can ZipAlign the signed apk to compress it.
Usage:
zipalign [-f] [-v] <alignment> infile.apk outfile.apk
Example:
D:\android-sdk\android-sdk\tools>zipalign -f -v 4 "C:\Users\Joisar\Desktop\project_name\appname_signed.apk" "C:\Users\Joisar\Desktop\project_name\appname__zipaligned.apk"
Note:
Kindly checkout the apk whether it is zipaligned or not by following command, if it's not zipaligned, then do it.
zipalign -c -v 4 "C:\Users\Joisar\Desktop\project_name\appname_signed.apk"

Find the problem
You can Analyse APK from Android Studio. This shows you the various files in their directories and their sizes, both absolute and relative to the whole APK:
Check for Unused Resources
This is the easiest: shows you, among others, the unused resources:
Just remove them from your project.
Use Vector Images
Vector Drawables provide one sharp image for all resolutions, greatly reducing the size for your graphics. As usually, you can use these for icons etc, but not for Photos. Non-vectorized images can be reduced with trimage.
proguard minify
Add the following to app/build.gradle to enable proguard to reduce unused classes from your project:
buildTypes {
release {
minifyEnabled true
shrinkResources true
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}

Use .svg format icon set.
Compress PNGs.
Use only specific libraries of Google Play Services.
Use Proguard
build.gradle
android {
...
buildTypes {
release {
minifyEnabled true
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
Shrink Resources
build.gradle
android {
...
buildTypes {
release {
shrinkResources true
minifyEnabled true
...
}
}
}

The Apk file exported from Android Studio is too large

I have never used Android Studio before. The size of a simple "Hello world" app generated by default is almost 800k, while it is less than 100k in eclipse. I find that there are too many pictures in the drawable files, they seem come from res/all under the build folder, they still exist even if I delete the folder res manually.
My question is how to shrink the apk size in this situation?

The difference is due to the appcompat library which is compiled in by default to New Project Wizard-generated projects in Android Studio if you target an API level lower than 14. When I ran a test, the size increase was 642k for a debug APK, and 411k for a release APK (with Proguard enabled -- that will strip out unused code but not unused resources).
There's not a lot you can really do about this, short of removing the appcompat library if you're not using any of its features (though you should probably be using its features).

I haven't used Android Studio yet (my understanding is that it's still beta), but, I know that with other IDEs, the size of the resulting executable will change based on if it's a Debug or Release version. Eclipse lets you specify one or the other. Does Android Studio do the same?

Try to use "shrinkResources" in (build.gradle app)
buildTypes {
release {
minifyEnabled true
shrinkResources true
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
https://developer.android.com/topic/performance/reduce-apk-size