Building multiple APKs inside Android Studio

Build variants are a huge feature for Android development. The use cases for such a feature are many. It can be as simple as having a free version of your app and a paid version. Or maybe you are making generic software that can be sold to many companies that all want they're own branding.

Whatever your use case may be, Gradle comes to the rescue. Not only can you configure your variants but you can also select which ones actually get built. You are probably already aware of the standard way to do this in Android Studio which is to use the "Build Variants" tool window and select the variant that you want to build.

This builds one variant at a time and is very practical while you are developing as it allows you to quickly switch from one variant to the another.

Once development is done, you will want to build all of your release variants for final testing and distribution. You can do this in Android Studio as well. Simply open the "Gradle Tasks" tool window, which is usually on the right. You will see many tasks that start with 'assemble', double click on one of those and your APKs will be created.

For example, double clicking on 'assembleRelease' will create all your release apks.

From the docs:

Building and Tasks

We previously saw that each Build Type creates its own assemble task, but that Build Variants are a combination of Build Type and Product Flavor.

When Product Flavors are used, more assemble-type tasks are created. These are:

1) assemble[Variant Name]

2) assemble[Build Type Name]

3) assemble[Product Flavor Name]

1) allows directly building a single variant. For instance assembleFlavor1Debug.

2) allows building all APKs for a given Build Type. For instance assembleDebug will build both Flavor1Debug and Flavor2Debug variants.

3) allows building all APKs for a given flavor. For instance assembleFlavor1 will build both Flavor1Debug and Flavor1Release variants.

The task assemble will build all possible variants.

Note the "Recent tasks" section which allows you to quickly execute previously run tasks.

You'll also note that the tasks that you run are added to your Configurations dropdown. This allows you to quickly access them by hitting Shift-F10.

And that's it! I hope that this helps you out.

Copying a template project

Today I fell upon a problem that really baffled me for a while.  Android Studio just refused to create my R class.  No lint problems, no compile problems (besides the missing R), nothing.  It just failed. I searched on the net but problems like that are difficult to find answers to because Android Studio is in such fluctuation that the answers no longer apply.

I tried cleaning my project. Rebuilding my project. It was then suggested that I invalidate my caches and restart Android Studio (you can find that in the File menu) but that didn't work.  I deleted my build directory. Nothing would work. Then it dawned on me...

I was trying to create a project from a template project that I created.  The Coloroos project will have many coloring books and each will require it's own project, so I wanted to create a template project and just copy paste it and go. What I did was copy and paste the project and then open it in Android Studio. There lies the problem. In order to properly reset everything I need to delete the .idea directory from the pasted project and then import it into Android Studio. Once I did that, it compiled and ran immediately.