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Android: preserve NestedScrollView fling nested-scroll lifecycle #57972

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Android: preserve NestedScrollView fling nested-scroll lifecycle #57972

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17 changes: 1 addition & 16 deletions ...ative/ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactNestedScrollView.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @generated SignedSource<<497c1f334f6b3325e032e09947f6fce4>>
* @generated SignedSource<<a38f03b5fd0c32076a46efce475b5598>>
*/

/**
Expand Down Expand Up @@ -706,21 +706,6 @@ constructor(context: Context, private val fpsListener: FpsListener? = null) :

if (pagingEnabled) {
flingAndSnap(correctedVelocityY)
} else if (scroller != null) {
val scrollWindowHeight = height - paddingBottom - paddingTop
scroller.fling(
scrollX, // startX
scrollY, // startY
0, // velocityX
correctedVelocityY, // velocityY
0, // minX
0, // maxX
0, // minY
Int.MAX_VALUE, // maxY
0, // overX
scrollWindowHeight / 2, // overY
)
postInvalidateOnAnimation()
} else {
super.fling(correctedVelocityY)
}
Expand Down
44 changes: 44 additions & 0 deletions ...ReactAndroid/src/main/java/com/facebook/react/views/scroll/generate-nested-scroll-view.js
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Original file line number Diff line number Diff line change
Expand Up @@ -100,6 +100,46 @@ function replaceCopyrightHeader(content, sourceFile) {
return content.replace(COPYRIGHT_HEADER_PATTERN, generatedHeader(sourceFile));
}

/**
* Keep NestedScrollView in charge of the non-paging fling lifecycle.
*
* ReactScrollView intentionally drives its reflected OverScroller directly. For
* the generated AndroidX variant, doing the same bypasses NestedScrollView.fling()
* and therefore its TYPE_NON_TOUCH nested-scroll lifecycle.
*/
function replaceNestedScrollViewFling(content) {
const scrollerFlingBranch = ` } else if (scroller != null) {
val scrollWindowHeight = height - paddingBottom - paddingTop
scroller.fling(
scrollX, // startX
scrollY, // startY
0, // velocityX
correctedVelocityY, // velocityY
0, // minX
0, // maxX
0, // minY
Int.MAX_VALUE, // maxY
0, // overX
scrollWindowHeight / 2, // overY
)
postInvalidateOnAnimation()
} else {
super.fling(correctedVelocityY)
}`;
const nestedScrollFlingBranch = ` } else {
super.fling(correctedVelocityY)
}`;
const occurrenceCount = content.split(scrollerFlingBranch).length - 1;

if (occurrenceCount !== 1) {
throw new Error(
`Expected exactly one ReactScrollView fling scroller branch; found ${occurrenceCount}.`,
);
}

return content.replace(scrollerFlingBranch, nestedScrollFlingBranch);
}

/**
* Transform ReactScrollView.kt to ReactNestedScrollView.kt
*/
Expand All @@ -121,6 +161,10 @@ function transformScrollView(content) {
// Replace ReactScrollView with ReactNestedScrollView
content = replaceClassNames(content);

// Unlike android.widget.ScrollView, AndroidX NestedScrollView owns the nested-scroll
// lifecycle of a fling. Preserve that lifecycle in the generated variant.
content = replaceNestedScrollViewFling(content);

// Make the class internal to keep it out of the public API
content = content.replace(
'public open class ReactNestedScrollView',
Expand Down