Unused images in android studio project are included in APK?

Question

Normally I’m not satisfied with the first image I put up as background, is from Activity, textView, button, etc. Even imageViews at last.

It happens that I leave them there in the project, even not using them, with the thought that at a given moment I may need them, whether for a test or even a comparison.

These are all the "drawable" images of a project of mine:

It turns out that when I went to pass the apk to my physical android device, I found the size of the apk very large compared to the application which is quite simple actually. So I came up with the idea of analyzing the apk, so I realized that the images, even those that were not being used, were being accounted for in the weight of the apk:

I honestly did not understand why they are included in apk. Engines of games like Unity for example, delete unused images and files from your executable and the application itself.

I would like to know the explanation for this, because for me there is no sense, should count in apk only what is used.

Answer 1

Not if you set your app build.Gradle for that purpose.

You should use the properties minifyEnabled and shrinkResources and "set them" with true:

android {
    ...
    buildTypes {
        release {
            shrinkResources true
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'),
                    'proguard-rules.pro'
        }
    }
}

Do this only in the final build, before creating the APK for distribution, as this increases the time of build.

For more information see Shrink Your Resources, in the documentation.