Layout Inspectorと再コンポジション回数

Performance tuning starts with data. Android Studio shows exactly which Composables recompose and how often, so you fix real problems.

The Layout Inspector attaches to a running app and renders a live tree of every Composable currently on screen.

Enable the recomposition counter to see two numbers per node: total recompositions and how many of those were skipped.

A node recomposing hundreds of times while you barely interact is a hotspot worth investigating for unstable inputs.

A healthy Composable shows many skips. Zero skips next to a high recomposition count means stability is broken somewhere.

You can reset the counts, perform one action, then read the deltas. Isolating a single interaction makes the data easy to read.

The compiler metrics report lists every Composable as restartable, skippable, or not, plus why each parameter is unstable.

The reports name the exact class Compose sees as unstable, pointing you straight at the type that needs val or an annotation.

Use the inspector to spot a hotspot, then the compiler report to learn why it cannot skip. Together they close the loop.

Measure performance on a release build, not debug. Debug Compose runs extra checks that distort real recomposition timing.

After a fix, re-run the inspector to confirm skips went up. Always verify the change with numbers before moving on.

Check your tooling knowledge.

Use Layout Inspector counts and compiler reports to find real hotspots, fix the unstable cause, then re-measure to prove it. ✅