Added LargeTopAppBarNestedScrollConnection (ccb47564) · Commits · e / os / android_frameworks_base

packages/SystemUI/compose/core/src/com/android/compose/nestedscroll/LargeTopAppBarNestedScrollConnection.kt

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		/*
		* Copyright (C) 2023 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		package com.android.compose.nestedscroll

		import androidx.compose.ui.geometry.Offset
		import androidx.compose.ui.input.nestedscroll.NestedScrollConnection
		import androidx.compose.ui.input.nestedscroll.NestedScrollSource

		/**
		* A [NestedScrollConnection] that listens for all vertical scroll events and responds in the
		* following way:
		* - If you scroll up, it first brings the [height] back to the [minHeight] and then allows
		* scrolling of the children (usually the content).
		* - If you scroll down, it first allows scrolling of the children (usually the content) and
		* then resets the [height] to [maxHeight].
		*
		* This behavior is useful for implementing a
		* [Large top app bar](https://m3.material.io/components/top-app-bar/specs) effect or something
		* similar.
		*
		* @sample com.android.compose.animation.scene.demo.Shade
		*/
		class LargeTopAppBarNestedScrollConnection(
		private val height: () -> Float,
		private val onChangeHeight: (Float) -> Unit,
		private val minHeight: Float,
		private val maxHeight: Float,
		) : NestedScrollConnection {

		constructor(
		height: () -> Float,
		onHeightChanged: (Float) -> Unit,
		heightRange: ClosedFloatingPointRange<Float>,
		) : this(
		height = height,
		onChangeHeight = onHeightChanged,
		minHeight = heightRange.start,
		maxHeight = heightRange.endInclusive,
		)

		/**
		* When swiping up, the LargeTopAppBar will shrink (to [minHeight]) and the content will expand.
		* Then, you can then scroll down the content.
		*/
		override fun onPreScroll(available: Offset, source: NestedScrollSource): Offset {
		val y = available.y
		val currentHeight = height()
		if (y >= 0 \|\| currentHeight <= minHeight) {
		return Offset.Zero
		}

		val amountLeft = minHeight - currentHeight
		val amountConsumed = y.coerceAtLeast(amountLeft)
		onChangeHeight(currentHeight + amountConsumed)
		return Offset(0f, amountConsumed)
		}

		/**
		* When swiping down, the content will scroll up until it reaches the top. Then, the
		* LargeTopAppBar will expand until it reaches its [maxHeight].
		*/
		override fun onPostScroll(
		consumed: Offset,
		available: Offset,
		source: NestedScrollSource
		): Offset {
		val y = available.y
		val currentHeight = height()
		if (y <= 0 \|\| currentHeight >= maxHeight) {
		return Offset.Zero
		}

		val amountLeft = maxHeight - currentHeight
		val amountConsumed = y.coerceAtMost(amountLeft)
		onChangeHeight(currentHeight + amountConsumed)
		return Offset(0f, amountConsumed)
		}
		}

packages/SystemUI/compose/core/tests/src/com/android/compose/nestedscroll/LargeTopAppBarNestedScrollConnectionTest.kt

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		/*
		* Copyright (C) 2023 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		package com.android.compose.nestedscroll

		import androidx.compose.ui.geometry.Offset
		import androidx.compose.ui.input.nestedscroll.NestedScrollSource
		import com.google.common.truth.Truth.assertThat
		import org.junit.Test
		import org.junit.runner.RunWith
		import org.junit.runners.Parameterized

		@RunWith(Parameterized::class)
		class LargeTopAppBarNestedScrollConnectionTest(testCase: TestCase) {
		val scrollSource = testCase.scrollSource

		private var height = 0f

		private fun buildScrollConnection(heightRange: ClosedFloatingPointRange<Float>) =
		LargeTopAppBarNestedScrollConnection(
		height = { height },
		onHeightChanged = { height = it },
		heightRange = heightRange,
		)

		@Test
		fun onScrollUp_consumeHeightFirst() {
		val scrollConnection = buildScrollConnection(heightRange = 0f..2f)
		height = 1f

		val offsetConsumed =
		scrollConnection.onPreScroll(available = Offset(x = 0f, y = -1f), source = scrollSource)

		// It can decrease by 1 the height
		assertThat(offsetConsumed).isEqualTo(Offset(0f, -1f))
		assertThat(height).isEqualTo(0f)
		}

		@Test
		fun onScrollUp_consumeDownToMin() {
		val scrollConnection = buildScrollConnection(heightRange = 0f..2f)
		height = 0f

		val offsetConsumed =
		scrollConnection.onPreScroll(available = Offset(x = 0f, y = -1f), source = scrollSource)

		// It should not change the height (already at min)
		assertThat(offsetConsumed).isEqualTo(Offset.Zero)
		assertThat(height).isEqualTo(0f)
		}

		@Test
		fun onScrollUp_ignorePostScroll() {
		val scrollConnection = buildScrollConnection(heightRange = 0f..2f)
		height = 1f

		val offsetConsumed =
		scrollConnection.onPostScroll(
		consumed = Offset.Zero,
		available = Offset(x = 0f, y = -1f),
		source = scrollSource
		)

		// It should ignore all onPostScroll events
		assertThat(offsetConsumed).isEqualTo(Offset.Zero)
		assertThat(height).isEqualTo(1f)
		}

		@Test
		fun onScrollDown_allowConsumeContentFirst() {
		val scrollConnection = buildScrollConnection(heightRange = 0f..2f)
		height = 1f

		val offsetConsumed =
		scrollConnection.onPreScroll(available = Offset(x = 0f, y = 1f), source = scrollSource)

		// It should ignore all onPreScroll events
		assertThat(offsetConsumed).isEqualTo(Offset.Zero)
		assertThat(height).isEqualTo(1f)
		}

		@Test
		fun onScrollDown_consumeHeightPostScroll() {
		val scrollConnection = buildScrollConnection(heightRange = 0f..2f)
		height = 1f

		val offsetConsumed =
		scrollConnection.onPostScroll(
		consumed = Offset.Zero,
		available = Offset(x = 0f, y = 1f),
		source = scrollSource
		)

		// It can increase by 1 the height
		assertThat(offsetConsumed).isEqualTo(Offset(0f, 1f))
		assertThat(height).isEqualTo(2f)
		}

		@Test
		fun onScrollDown_consumeUpToMax() {
		val scrollConnection = buildScrollConnection(heightRange = 0f..2f)
		height = 2f

		val offsetConsumed =
		scrollConnection.onPostScroll(
		consumed = Offset.Zero,
		available = Offset(x = 0f, y = 1f),
		source = scrollSource
		)

		// It should not change the height (already at max)
		assertThat(offsetConsumed).isEqualTo(Offset.Zero)
		assertThat(height).isEqualTo(2f)
		}

		// NestedScroll Source is a value/inline class and must be wrapped in a parameterized test
		// https://youtrack.jetbrains.com/issue/KT-35523/Parameterized-JUnit-tests-with-inline-classes-throw-IllegalArgumentException
		data class TestCase(val scrollSource: NestedScrollSource) {
		override fun toString() = scrollSource.toString()
		}

		companion object {
		@Parameterized.Parameters(name = "{0}")
		@JvmStatic
		fun data(): List<TestCase> =
		listOf(
		TestCase(NestedScrollSource.Drag),
		TestCase(NestedScrollSource.Fling),
		TestCase(NestedScrollSource.Wheel),
		)
		}
		}