Performance, accessibility and Play quality

Startup and jank measurement, baseline profiles, leak detection, TalkBack and contrast, and the Play vitals that affect distribution.

Startup and jank

// macrobenchmark: measure cold start on a real device
@RunWith(AndroidJUnit4::class)
class StartupBenchmark {
    @get:Rule val rule = MacrobenchmarkRule()

    @Test fun coldStartup() = rule.measureRepeated(
        packageName = "com.example.app",
        metrics = listOf(StartupTimingMetric(), FrameTimingMetric()),
        iterations = 10,
        startupMode = StartupMode.COLD,
        compilationMode = CompilationMode.Partial(),
    ) {
        pressHome()
        startActivityAndWait()
    }
}

// Baseline profile: precompiled code paths, generated by the same run
@RunWith(AndroidJUnit4::class)
class BaselineProfileGenerator {
    @get:Rule val rule = BaselineProfileRule()

    @Test fun profile() = rule.collect("com.example.app") {
        pressHome()
        startActivityAndWait()
        device.findObject(By.text("Books")).click()
        device.waitForIdle()
    }
}

• Measure on a release build on a physical low-end device. Debug builds are more than ten times slower and hide the problems you are trying to find.
• A baseline profile is the highest-leverage performance change available: it typically cuts startup and jank by a large fraction with no code changes.
• Do work off the main thread even if it is fast. A 50 ms JSON parse on the main thread is a dropped frame, and on a slow device it is three.

Memory and leaks

• Add LeakCanary in debug builds. It reports a retained Activity with the path that keeps it alive, which is almost always an anonymous listener, a coroutine in a global scope, or a static reference.
• Cancel coroutines with the right scope. A GlobalScope launch holding a Context is a leak with a delay fuse.
• Unregister every listener: lifecycle observers, sensor callbacks, broadcast receivers, database cursors.
• Watch bitmap memory. An image decoded at full resolution and scaled down in the view costs many times what a correctly sampled decode costs.
• Use WindowManager to check for a heavy layout. Deeply nested views inflate measure and layout time, and Compose's LazyColumn exists to avoid rendering what is off screen.

// decode at the size you will display
val options = BitmapFactory.Options().apply { inJustDecodeBounds = true }
BitmapFactory.decodeFile(path, options)
options.inSampleSize = calculateInSampleSize(options, targetWidth, targetHeight)
options.inJustDecodeBounds = false
val bitmap = BitmapFactory.decodeFile(path, options)

// show large images with a library that owns the cache
// Coil, with a size hint so the decode matches the slot
AsyncImage(
    model = ImageRequest.Builder(context).data(url).size(400).crossfade(true).build(),
    contentDescription = null,
)

Accessibility and Play quality

// a decorative image
Icon(Icons.Default.Star, contentDescription = null)

// a meaningful image or icon button
IconButton(onClick = onShare, modifier = Modifier.semantics { }) {
    Icon(Icons.Default.Share, contentDescription = "Share this book")
}

// merge a row into one focusable announcement
Row(Modifier.semantics(mergeDescendants = true) {}) {
    Text(book.title)
    Text(book.author)
}

// a heading so TalkBack navigation can jump to it
Text("Latest", Modifier.semantics { heading() })

// custom actions for a gesture-heavy widget
Box(Modifier.semantics {
    customActions = listOf(CustomAccessibilityAction("Delete") { onDelete(); true })
})

• Every interactive element needs a minimum touch target of 48 dp, and every icon-only control needs a content description that says what it does, not what it looks like.
• Support font scaling: test at 200 percent. A fixed-height row with text in it clips, and a hard-coded sp in a small box is where accessibility and design argue.
• Contrast matters: 4.5:1 for body text, 3:1 for large text. Material's colour roles are designed for this, which is why a hard-coded hex value breaks it.
• Test with TalkBack and with a keyboard, and run the Accessibility Scanner over your main screens.

# Play vitals that affect search and promotion
#   ANR rate            crashes and freezes in the foreground
#   crash rate          including background crashes
#   excessive wakeups   battery drain reported by the platform
#   stuck partial wakelocks
#
# and store requirements, which change every year:
#   targetSdk within the current window
#   a privacy policy for anything collecting data
#   a data safety declaration that matches the SDKs you ship

Run the pre-launch report before every release. It tests on real devices, flags crashes, accessibility issues and excessive permissions, and it is free - shipping without reading it means your users find those problems first.

FAQ

Related

Testing Android apps Permissions, storage and publishing

Last refreshed 2026-09-18.