Avoiding unnecessary recomposition.
WHAT CAUSES POOR PERFORMANCE
Recomposing more than necessary Expensive work during composition Reading state at too high a level Unstable parameters
WHAT UNSTABLE MEANS
A type Compose cannot determine is unchanged, so it assumes it changed.
WHAT CAUSES IT
Mutable collections Types from modules Compose cannot analyse Lambdas capturing changing values
WHAT TO PREFER
Immutable data Stable collection types
WHAT READING STATE AT TOO HIGH A LEVEL CAUSES
A large portion of the interface recomposing when a small part changed.
WHAT TO DO ABOUT IT
Read the state as close as possible to where it is used, by passing a function rather than a value where appropriate.
WHAT TO MEASURE WITH
The layout inspector and recomposition counts.
WHY MEASURE
Guessing about recomposition is unreliable.
WHAT TO AVOID
Optimising before measuring Heavy computation during composition
WHAT TO MOVE
Computation into remembered values, or into the view model.
WHAT TO TEST ON
A modest device, where the cost is visible.
