performance-optimization

Performance Optimization

Overview

"Performance optimization without measurement is guessing." Measure first, identify bottlenecks with data, fix with targeted changes, verify the improvement, and guard against regressions. Never optimize based on assumptions.

When to Use

• App startup exceeds 500ms (cold) or 200ms (warm)
• UI jank (dropped frames, janky scrolling)
• ANR (Application Not Responding) reports
• APK/AAB size exceeds budget
• Before a release (performance regression check)
• Users report slowness or battery drain

Skip when: No performance issue is observed or measured.

Android Vitals Targets

Metric	Target	Critical
Cold startup	< 500ms	> 1s
Warm startup	< 200ms	> 500ms
Frame rendering (jank)	< 5% slow frames	> 10% slow frames
ANR rate	< 0.47%	> 1%
APK size (compressed)	< 10MB	> 50MB
Memory usage	< 150MB typical	> 256MB

Core Process

Step 1: Measure

1. Baseline Profiles (startup and scrolling):

// benchmark/src/main/java/BaselineProfileGenerator.kt
@RunWith(AndroidJUnit4::class)
class BaselineProfileGenerator {
    @get:Rule
    val rule = BaselineProfileRule()

    @Test
    fun generateBaselineProfile() {
        rule.collect(packageName = "com.example.app") {
            // Cold start
            pressHome()
            startActivityAndWait()

            // Critical user journeys
            device.findObject(By.text("Tasks")).click()
            device.waitForIdle()

            // Scroll the list
            val list = device.findObject(By.res("task_list"))
            list.setGestureMargin(device.displayWidth / 5)
            list.fling(Direction.DOWN)
            device.waitForIdle()
        }
    }
}

1. Macrobenchmark (startup timing):

@RunWith(AndroidJUnit4::class)
class StartupBenchmark {
    @get:Rule
    val rule = MacrobenchmarkRule()

    @Test
    fun coldStartup() {
        rule.measureRepeated(
            packageName = "com.example.app",
            metrics = listOf(StartupTimingMetric()),
            startupMode = StartupMode.COLD,
            iterations = 5,
        ) {
            pressHome()
            startActivityAndWait()
        }
    }
}