Fix maintainVisibleContentPosition when ScrollView content shrinks #58695
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,116 @@ | ||
| /* | ||
| * Copyright (c) Meta Platforms, Inc. and affiliates. | ||
| * | ||
| * This source code is licensed under the MIT license found in the | ||
| * LICENSE file in the root directory of this source tree. | ||
| */ | ||
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| package com.facebook.react.views.scroll | ||
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| import android.content.Context | ||
| import android.view.View | ||
| import android.widget.FrameLayout | ||
| import com.facebook.react.bridge.UIManager | ||
| import com.facebook.react.internal.featureflags.ReactNativeFeatureFlagsForTests | ||
| import com.facebook.react.views.scroll.ReactScrollViewHelper.HasScrollEventThrottle | ||
| import com.facebook.react.views.scroll.ReactScrollViewHelper.HasSmoothScroll | ||
| import com.facebook.react.views.view.ReactViewGroup | ||
| import org.assertj.core.api.Assertions.assertThat | ||
| import org.junit.Before | ||
| import org.junit.Test | ||
| import org.junit.runner.RunWith | ||
| import org.mockito.kotlin.mock | ||
| import org.robolectric.RobolectricTestRunner | ||
| import org.robolectric.RuntimeEnvironment | ||
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| @RunWith(RobolectricTestRunner::class) | ||
| class MaintainVisibleScrollPositionHelperTest { | ||
| private lateinit var context: Context | ||
| private val uiManager: UIManager = mock() | ||
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| @Before | ||
| fun setUp() { | ||
| ReactNativeFeatureFlagsForTests.setUp() | ||
| context = RuntimeEnvironment.getApplication() | ||
| } | ||
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| @Test | ||
| fun shrinkingContentAdjustsFromOffsetBeforeLayoutClamp() { | ||
| val scrollView = TestScrollView(context) | ||
| val content = ReactViewGroup(context) | ||
| val anchor = View(context) | ||
| content.addView(anchor) | ||
| scrollView.addView(content) | ||
| anchor.layout(0, 900, 100, 1000) | ||
| scrollView.scrollTo(0, 900) | ||
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| val helper = MaintainVisibleScrollPositionHelper(scrollView, horizontal = false) | ||
| helper.config = MaintainVisibleScrollPositionHelper.Config(0, null) | ||
| helper.willMountItems(uiManager) | ||
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| anchor.layout(0, 300, 100, 400) | ||
| scrollView.scrollTo(0, 100) // Layout clamped the old offset before didMountItems. | ||
| helper.didMountItems(uiManager) | ||
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| assertThat(scrollView.requestedY).isEqualTo(300) | ||
| } | ||
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| @Test | ||
| fun shrinkingHorizontalContentAdjustsFromOffsetBeforeLayoutClamp() { | ||
| val scrollView = TestScrollView(context) | ||
| val content = ReactViewGroup(context) | ||
| val anchor = View(context) | ||
| content.addView(anchor) | ||
| scrollView.addView(content) | ||
| anchor.layout(900, 0, 1000, 100) | ||
| scrollView.scrollTo(900, 0) | ||
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| val helper = MaintainVisibleScrollPositionHelper(scrollView, horizontal = true) | ||
| helper.config = MaintainVisibleScrollPositionHelper.Config(0, null) | ||
| helper.willMountItems(uiManager) | ||
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| anchor.layout(300, 0, 400, 100) | ||
| scrollView.scrollTo(100, 0) | ||
| helper.didMountItems(uiManager) | ||
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| assertThat(scrollView.requestedX).isEqualTo(300) | ||
| } | ||
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| @Test | ||
| fun growingContentStillAdjustsFromOffsetBeforeMount() { | ||
| val scrollView = TestScrollView(context) | ||
| val content = ReactViewGroup(context) | ||
| val anchor = View(context) | ||
| content.addView(anchor) | ||
| scrollView.addView(content) | ||
| anchor.layout(0, 300, 100, 400) | ||
| scrollView.scrollTo(0, 300) | ||
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| val helper = MaintainVisibleScrollPositionHelper(scrollView, horizontal = false) | ||
| helper.config = MaintainVisibleScrollPositionHelper.Config(0, null) | ||
| helper.willMountItems(uiManager) | ||
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| anchor.layout(0, 900, 100, 1000) | ||
| helper.didMountItems(uiManager) | ||
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| assertThat(scrollView.requestedY).isEqualTo(900) | ||
| } | ||
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| private class TestScrollView(context: Context) : | ||
| FrameLayout(context), HasScrollEventThrottle, HasSmoothScroll { | ||
| override var scrollEventThrottle: Int = 0 | ||
| override var lastScrollDispatchTime: Long = 0 | ||
| var requestedX: Int? = null | ||
| var requestedY: Int? = null | ||
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| override fun reactSmoothScrollTo(x: Int, y: Int) { | ||
| scrollTo(x, y) | ||
| } | ||
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| override fun scrollToPreservingMomentum(x: Int, y: Int) { | ||
| requestedX = x | ||
| requestedY = y | ||
| scrollTo(x, y) | ||
| } | ||
| } | ||
| } |
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With this, it's possible to have the content offset greater than the height of the scroll view and you end up overscrolling. The target offset should be clamped to the bounds of the scroll view. You can use a helper like this to precompute the target point:
and then the correction becomes
CGPoint targetOffset = CGPointMake( x + deltaX, _scrollView.contentOffset.y); [self _forceDispatchNextScrollEvent]; _scrollView.contentOffset = RCTClampMaintainVisibleContentOffset(_scrollView, targetOffset);(same for vertical as well)