Merge "Creates throttle function for flows" into tm-qpr-dev (93470241) · Commits · e / os / android_frameworks_base

packages/SystemUI/src/com/android/systemui/util/kotlin/Flow.kt

+93 −0

Original line number	Original line	Diff line number	Diff line
	@@ -16,14 +16,21 @@

	package com.android.systemui.util.kotlin		package com.android.systemui.util.kotlin

			import com.android.systemui.util.time.SystemClock
			import com.android.systemui.util.time.SystemClockImpl
			import kotlinx.coroutines.CoroutineStart
	import java.util.concurrent.atomic.AtomicReference		import java.util.concurrent.atomic.AtomicReference
	import kotlinx.coroutines.Dispatchers		import kotlinx.coroutines.Dispatchers
			import kotlinx.coroutines.Job
	import kotlinx.coroutines.coroutineScope		import kotlinx.coroutines.coroutineScope
			import kotlinx.coroutines.delay
	import kotlinx.coroutines.flow.Flow		import kotlinx.coroutines.flow.Flow
			import kotlinx.coroutines.flow.channelFlow
	import kotlinx.coroutines.flow.distinctUntilChanged		import kotlinx.coroutines.flow.distinctUntilChanged
	import kotlinx.coroutines.flow.flow		import kotlinx.coroutines.flow.flow
	import kotlinx.coroutines.flow.onStart		import kotlinx.coroutines.flow.onStart
	import kotlinx.coroutines.launch		import kotlinx.coroutines.launch
			import kotlin.math.max

	/**		/**
	* Returns a new [Flow] that combines the two most recent emissions from [this] using [transform].		* Returns a new [Flow] that combines the two most recent emissions from [this] using [transform].
	@@ -167,3 +174,89 @@ fun <A, B, C> Flow<A>.sample(other: Flow<B>, transform: suspend (A, B) -> C): Fl
	* Note that the returned Flow will not emit anything until [other] has emitted at least one value.		* Note that the returned Flow will not emit anything until [other] has emitted at least one value.
	*/		*/
	fun <A> Flow<*>.sample(other: Flow<A>): Flow<A> = sample(other) { _, a -> a }		fun <A> Flow<*>.sample(other: Flow<A>): Flow<A> = sample(other) { _, a -> a }

			/**
			* Returns a flow that mirrors the original flow, but delays values following emitted values for the
			* given [periodMs]. If the original flow emits more than one value during this period, only the
			* latest value is emitted.
			*
			* Example:
			*
			* ```kotlin
			* flow {
			* emit(1) // t=0ms
			* delay(90)
			* emit(2) // t=90ms
			* delay(90)
			* emit(3) // t=180ms
			* delay(1010)
			* emit(4) // t=1190ms
			* delay(1010)
			* emit(5) // t=2200ms
			* }.throttle(1000)
			* ```
			*
			* produces the following emissions at the following times
			*
			* ```text
			* 1 (t=0ms), 3 (t=1000ms), 4 (t=2000ms), 5 (t=3000ms)
			* ```
			*/
			fun <T> Flow<T>.throttle(periodMs: Long): Flow<T> = this.throttle(periodMs, SystemClockImpl())

			/**
			* Returns a flow that mirrors the original flow, but delays values following emitted values for the
			* given [periodMs] as reported by the given [clock]. If the original flow emits more than one value
			* during this period, only The latest value is emitted.
			*
			* Example:
			*
			* ```kotlin
			* flow {
			* emit(1) // t=0ms
			* delay(90)
			* emit(2) // t=90ms
			* delay(90)
			* emit(3) // t=180ms
			* delay(1010)
			* emit(4) // t=1190ms
			* delay(1010)
			* emit(5) // t=2200ms
			* }.throttle(1000)
			* ```
			*
			* produces the following emissions at the following times
			*
			* ```text
			* 1 (t=0ms), 3 (t=1000ms), 4 (t=2000ms), 5 (t=3000ms)
			* ```
			*/
			fun <T> Flow<T>.throttle(periodMs: Long, clock: SystemClock): Flow<T> = channelFlow {
			coroutineScope {
			var previousEmitTimeMs = 0L
			var delayJob: Job? = null
			var sendJob: Job? = null
			val outerScope = this

			collect {
			delayJob?.cancel()
			sendJob?.join()
			val currentTimeMs = clock.elapsedRealtime()
			val timeSinceLastEmit = currentTimeMs - previousEmitTimeMs
			val timeUntilNextEmit = max(0L, periodMs - timeSinceLastEmit)
			if (timeUntilNextEmit > 0L) {
			// We create delayJob to allow cancellation during the delay period
			delayJob = launch {
			delay(timeUntilNextEmit)
			sendJob = outerScope.launch(start = CoroutineStart.UNDISPATCHED) {
			send(it)
			previousEmitTimeMs = clock.elapsedRealtime()
			}
			}
			} else {
			send(it)
			previousEmitTimeMs = currentTimeMs
			}
			}
			}
			}
			No newline at end of file

packages/SystemUI/tests/src/com/android/systemui/util/kotlin/FlowUtilTests.kt

+171 −0

Original line number	Original line	Diff line number	Diff line
	@@ -19,9 +19,12 @@ package com.android.systemui.util.kotlin
	import android.testing.AndroidTestingRunner		import android.testing.AndroidTestingRunner
	import androidx.test.filters.SmallTest		import androidx.test.filters.SmallTest
	import com.android.systemui.SysuiTestCase		import com.android.systemui.SysuiTestCase
			import com.android.systemui.util.time.FakeSystemClock
	import com.google.common.truth.Truth.assertThat		import com.google.common.truth.Truth.assertThat
	import kotlinx.coroutines.Dispatchers		import kotlinx.coroutines.Dispatchers
			import kotlinx.coroutines.ExperimentalCoroutinesApi
	import kotlinx.coroutines.Job		import kotlinx.coroutines.Job
			import kotlinx.coroutines.delay
	import kotlinx.coroutines.flow.Flow		import kotlinx.coroutines.flow.Flow
	import kotlinx.coroutines.flow.MutableSharedFlow		import kotlinx.coroutines.flow.MutableSharedFlow
	import kotlinx.coroutines.flow.MutableStateFlow		import kotlinx.coroutines.flow.MutableStateFlow
	@@ -35,6 +38,10 @@ import kotlinx.coroutines.flow.takeWhile
	import kotlinx.coroutines.flow.toList		import kotlinx.coroutines.flow.toList
	import kotlinx.coroutines.launch		import kotlinx.coroutines.launch
	import kotlinx.coroutines.runBlocking		import kotlinx.coroutines.runBlocking
			import kotlinx.coroutines.test.TestScope
			import kotlinx.coroutines.test.advanceTimeBy
			import kotlinx.coroutines.test.runCurrent
			import kotlinx.coroutines.test.runTest
	import kotlinx.coroutines.yield		import kotlinx.coroutines.yield
	import org.junit.Test		import org.junit.Test
	import org.junit.runner.RunWith		import org.junit.runner.RunWith
	@@ -231,6 +238,170 @@ class SampleFlowTest : SysuiTestCase() {
	}		}
	}		}

			@OptIn(ExperimentalCoroutinesApi::class)
			@SmallTest
			@RunWith(AndroidTestingRunner::class)
			class ThrottleFlowTest : SysuiTestCase() {

			@Test
			fun doesNotAffectEmissions_whenDelayAtLeastEqualToPeriod() = runTest {
			// Arrange
			val choreographer = createChoreographer(this)
			val output = mutableListOf<Int>()
			val collectJob = backgroundScope.launch {
			flow {
			emit(1)
			delay(1000)
			emit(2)
			}.throttle(1000, choreographer.fakeClock).toList(output)
			}

			// Act
			choreographer.advanceAndRun(0)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(999)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(1)

			// Assert
			assertThat(output).containsExactly(1, 2)

			// Cleanup
			collectJob.cancel()
			}

			@Test
			fun delaysEmissions_withShorterThanPeriodDelay_untilPeriodElapses() = runTest {
			// Arrange
			val choreographer = createChoreographer(this)
			val output = mutableListOf<Int>()
			val collectJob = backgroundScope.launch {
			flow {
			emit(1)
			delay(500)
			emit(2)
			}.throttle(1000, choreographer.fakeClock).toList(output)
			}

			// Act
			choreographer.advanceAndRun(0)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(500)
			choreographer.advanceAndRun(499)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(1)

			// Assert
			assertThat(output).containsExactly(1, 2)

			// Cleanup
			collectJob.cancel()
			}

			@Test
			fun filtersAllButLastEmission_whenMultipleEmissionsInPeriod() = runTest {
			// Arrange
			val choreographer = createChoreographer(this)
			val output = mutableListOf<Int>()
			val collectJob = backgroundScope.launch {
			flow {
			emit(1)
			delay(500)
			emit(2)
			delay(500)
			emit(3)
			}.throttle(1000, choreographer.fakeClock).toList(output)
			}

			// Act
			choreographer.advanceAndRun(0)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(500)
			choreographer.advanceAndRun(499)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(1)

			// Assert
			assertThat(output).containsExactly(1, 3)

			// Cleanup
			collectJob.cancel()
			}

			@Test
			fun filtersAllButLastEmission_andDelaysIt_whenMultipleEmissionsInShorterThanPeriod() = runTest {
			// Arrange
			val choreographer = createChoreographer(this)
			val output = mutableListOf<Int>()
			val collectJob = backgroundScope.launch {
			flow {
			emit(1)
			delay(500)
			emit(2)
			delay(250)
			emit(3)
			}.throttle(1000, choreographer.fakeClock).toList(output)
			}

			// Act
			choreographer.advanceAndRun(0)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(500)
			choreographer.advanceAndRun(250)
			choreographer.advanceAndRun(249)

			// Assert
			assertThat(output).containsExactly(1)

			// Act
			choreographer.advanceAndRun(1)

			// Assert
			assertThat(output).containsExactly(1, 3)

			// Cleanup
			collectJob.cancel()
			}

			private fun createChoreographer(testScope: TestScope) = object {
			val fakeClock = FakeSystemClock()

			fun advanceAndRun(millis: Long) {
			fakeClock.advanceTime(millis)
			testScope.advanceTimeBy(millis)
			testScope.runCurrent()
			}
			}
			}

	private fun <T> assertThatFlow(flow: Flow<T>) =		private fun <T> assertThatFlow(flow: Flow<T>) =
	object {		object {
	suspend fun emitsExactly(vararg emissions: T) =		suspend fun emitsExactly(vararg emissions: T) =