Inventory is made with Android Studio. In order for you to make Inventory using Android Studio there are three things to do: one thing can be done before cloning Inventory while two must be done after cloning.

Before Cloning: Install SDK Components

If Android Studio doesn't already have the required SDK components then they must be installed. The required SDK components are

• SDK Platforms
  • Android 10.0 (Q)
    • Android SDK Platform 29
    • (a system image if you're going to use an AVD)
• SDK Tools
  • Android SDK Build-Tools
    • 29.0.2

After Cloning

sdk.dir

If Android Studio doesn't do it for you then create a text file called local.properties and put it in the Inventory Android project's root directory. Inside local.properties add a line similar to this one:

sdk.dir = /Users/peterrosario/Library/Android/sdk/

This line works for me because my username is peterrosario and I am using macOS. You will likely need a different line since your username is probably not the same as mine and you may not be using macOS.

There is an entry for this file in Inventory's .gitignore file.