Predict the output
Two build types (debug, release) and two flavor dimensions: tier (free, paid) and env (staging, prod). How many variants?
Multiply the counts.
Choose an answer, then open Show answer below to check it.
Answer: A 8
Correct. 2 × 2 × 2 = 8 variants, like freeStagingDebug.
Build types describe how you build, such as debug and release (signing, minification, debuggable). Product flavors describe what you build, such as free and paid, or staging and production, each with its own applicationId suffix, resources or code. Gradle combines them into variants, like freeRelease. Each variant can have its own source set, src/free/.
Explain build variants.
Say your answer out loud, then check which of these points you covered:
Flavors need a dimension; multiple dimensions multiply variants.
buildConfigField adds values to BuildConfig per variant (BuildConfig generation must be switched on).
Use androidComponents { beforeVariants { } } to disable variants you don't need.
Too many variants slow builds and CI.
Define 'how' vs 'what', then the combination rule.
Think of your answer first, then open the hint.
How many variants do 2 build types and 3 flavors give?
Six.
Where does flavor-specific code live?
In src/<flavor>/java or kotlin.
Free tool
Free tool: read the SHA-1 and SHA-256 fingerprints from a .jks, .p12, APK or certificate, for API key restrictions and signing setups.
Suggest a fix if something here is wrong or out of date.