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react-native/React/Views/RCTScrollView.m

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/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
#import "RCTScrollView.h"
#import <UIKit/UIKit.h>
#import "RCTConvert.h"
#import "RCTEventDispatcher.h"
#import "RCTLog.h"
#import "RCTUIManager.h"
#import "RCTUtils.h"
#import "UIView+React.h"
CGFloat const ZINDEX_DEFAULT = 0;
CGFloat const ZINDEX_STICKY_HEADER = 50;
@interface RCTScrollEvent : NSObject <RCTEvent>
- (instancetype)initWithType:(RCTScrollEventType)type
reactTag:(NSNumber *)reactTag
scrollView:(UIScrollView *)scrollView
userData:(NSDictionary *)userData NS_DESIGNATED_INITIALIZER;
@end
@implementation RCTScrollEvent
{
RCTScrollEventType _type;
UIScrollView *_scrollView;
NSDictionary *_userData;
}
@synthesize viewTag = _viewTag;
- (instancetype)initWithType:(RCTScrollEventType)type
reactTag:(NSNumber *)reactTag
scrollView:(UIScrollView *)scrollView
userData:(NSDictionary *)userData
{
RCTAssertParam(reactTag);
if ((self = [super init])) {
_type = type;
_viewTag = reactTag;
_scrollView = scrollView;
_userData = userData;
}
return self;
}
RCT_NOT_IMPLEMENTED(-init)
- (uint16_t)coalescingKey
{
return 0;
}
- (NSDictionary *)body
{
NSDictionary *body = @{
@"contentOffset": @{
@"x": @(_scrollView.contentOffset.x),
@"y": @(_scrollView.contentOffset.y)
},
@"contentInset": @{
@"top": @(_scrollView.contentInset.top),
@"left": @(_scrollView.contentInset.left),
@"bottom": @(_scrollView.contentInset.bottom),
@"right": @(_scrollView.contentInset.right)
},
@"contentSize": @{
@"width": @(_scrollView.contentSize.width),
@"height": @(_scrollView.contentSize.height)
},
@"layoutMeasurement": @{
@"width": @(_scrollView.frame.size.width),
@"height": @(_scrollView.frame.size.height)
},
@"zoomScale": @(_scrollView.zoomScale ?: 1),
};
if (_userData) {
NSMutableDictionary *mutableBody = [body mutableCopy];
[mutableBody addEntriesFromDictionary:_userData];
body = mutableBody;
}
return body;
}
- (NSString *)eventName
{
static NSString *events[] = {
@"topScrollBeginDrag",
@"topScroll",
@"topScrollEndDrag",
@"topMomentumScrollBegin",
@"topMomentumScrollEnd",
@"topScrollAnimationEnd",
};
return events[_type];
}
- (BOOL)canCoalesce
{
return YES;
}
- (RCTScrollEvent *)coalesceWithEvent:(RCTScrollEvent *)newEvent
{
NSArray *updatedChildFrames = [_userData[@"updatedChildFrames"] arrayByAddingObjectsFromArray:newEvent->_userData[@"updatedChildFrames"]];
if (updatedChildFrames) {
NSMutableDictionary *userData = [newEvent->_userData mutableCopy];
userData[@"updatedChildFrames"] = updatedChildFrames;
newEvent->_userData = userData;
}
return newEvent;
}
+ (NSString *)moduleDotMethod
{
return @"RCTEventEmitter.receiveEvent";
}
@end
/**
* Include a custom scroll view subclass because we want to limit certain
* default UIKit behaviors such as textFields automatically scrolling
* scroll views that contain them and support sticky headers.
*/
@interface RCTCustomScrollView : UIScrollView<UIGestureRecognizerDelegate>
@property (nonatomic, copy) NSIndexSet *stickyHeaderIndices;
@property (nonatomic, assign) BOOL centerContent;
@end
@implementation RCTCustomScrollView
- (instancetype)initWithFrame:(CGRect)frame
{
if ((self = [super initWithFrame:frame])) {
[self.panGestureRecognizer addTarget:self action:@selector(handleCustomPan:)];
}
return self;
}
- (UIView *)contentView
{
return ((RCTScrollView *)self.superview).contentView;
}
/**
* @return Whether or not the scroll view interaction should be blocked because
* JS was found to be the responder.
*/
- (BOOL)_shouldDisableScrollInteraction
{
// Since this may be called on every pan, we need to make sure to only climb
// the hierarchy on rare occasions.
UIView *JSResponder = [RCTUIManager JSResponder];
if (JSResponder && JSResponder != self.superview) {
BOOL superviewHasResponder = [self isDescendantOfView:JSResponder];
return superviewHasResponder;
}
return NO;
}
- (void)handleCustomPan:(__unused UIPanGestureRecognizer *)sender
{
if ([self _shouldDisableScrollInteraction]) {
self.panGestureRecognizer.enabled = NO;
self.panGestureRecognizer.enabled = YES;
// TODO: If mid bounce, animate the scroll view to a non-bounced position
// while disabling (but only if `stopScrollInteractionIfJSHasResponder` was
// called *during* a `pan`. Currently, it will just snap into place which
// is not so bad either.
// Another approach:
// self.scrollEnabled = NO;
// self.scrollEnabled = YES;
}
}
- (void)scrollRectToVisible:(__unused CGRect)rect animated:(__unused BOOL)animated
{
// noop
}
/**
* Returning `YES` cancels touches for the "inner" `view` and causes a scroll.
* Returning `NO` causes touches to be directed to that inner view and prevents
* the scroll view from scrolling.
*
* `YES` -> Allows scrolling.
* `NO` -> Doesn't allow scrolling.
*
* By default this returns NO for all views that are UIControls and YES for
* everything else. What that does is allows scroll views to scroll even when a
* touch started inside of a `UIControl` (`UIButton` etc). For React scroll
* views, we want the default to be the same behavior as `UIControl`s so we
* return `YES` by default. But there's one case where we want to block the
* scrolling no matter what: When JS believes it has its own responder lock on
* a view that is *above* the scroll view in the hierarchy. So we abuse this
* `touchesShouldCancelInContentView` API in order to stop the scroll view from
* scrolling in this case.
*
* We are not aware of *any* other solution to the problem because alternative
* approaches require that we disable the scrollview *before* touches begin or
* move. This approach (`touchesShouldCancelInContentView`) works even if the
* JS responder is set after touches start/move because
* `touchesShouldCancelInContentView` is called as soon as the scroll view has
* been touched and dragged *just* far enough to decide to begin the "drag"
* movement of the scroll interaction. Returning `NO`, will cause the drag
* operation to fail.
*
* `touchesShouldCancelInContentView` will stop the *initialization* of a
* scroll pan gesture and most of the time this is sufficient. On rare
* occasion, the scroll gesture would have already initialized right before JS
* notifies native of the JS responder being set. In order to recover from that
* timing issue we have a fallback that kills any ongoing pan gesture that
* occurs when native is notified of a JS responder.
*
* Note: Explicitly returning `YES`, instead of relying on the default fixes
* (at least) one bug where if you have a UIControl inside a UIScrollView and
* tap on the UIControl and then start dragging (to scroll), it won't scroll.
* Chat with andras for more details.
*
* In order to have this called, you must have delaysContentTouches set to NO
* (which is the not the `UIKit` default).
*/
- (BOOL)touchesShouldCancelInContentView:(__unused UIView *)view
{
//TODO: shouldn't this call super if _shouldDisableScrollInteraction returns NO?
return ![self _shouldDisableScrollInteraction];
}
/*
* Automatically centers the content such that if the content is smaller than the
* ScrollView, we force it to be centered, but when you zoom or the content otherwise
* becomes larger than the ScrollView, there is no padding around the content but it
* can still fill the whole view.
*/
- (void)setContentOffset:(CGPoint)contentOffset
{
UIView *contentView = [self contentView];
if (contentView && _centerContent) {
CGSize subviewSize = contentView.frame.size;
CGSize scrollViewSize = self.bounds.size;
if (subviewSize.width < scrollViewSize.width) {
contentOffset.x = -(scrollViewSize.width - subviewSize.width) / 2.0;
}
if (subviewSize.height < scrollViewSize.height) {
contentOffset.y = -(scrollViewSize.height - subviewSize.height) / 2.0;
}
}
[super setContentOffset:contentOffset];
}
- (void)dockClosestSectionHeader
{
UIView *contentView = [self contentView];
CGFloat scrollTop = self.bounds.origin.y + self.contentInset.top;
// Find the section headers that need to be docked
__block UIView *previousHeader = nil;
__block UIView *currentHeader = nil;
__block UIView *nextHeader = nil;
NSUInteger subviewCount = contentView.reactSubviews.count;
[_stickyHeaderIndices enumerateIndexesWithOptions:0 usingBlock:
^(NSUInteger idx, __unused BOOL *stop) {
if (idx >= subviewCount) {
RCTLogError(@"Sticky header index %zd was outside the range {0, %zd}", idx, subviewCount);
return;
}
UIView *header = contentView.reactSubviews[idx];
// If nextHeader not yet found, search for docked headers
if (!nextHeader) {
CGFloat height = header.bounds.size.height;
CGFloat top = header.center.y - height * header.layer.anchorPoint.y;
if (top > scrollTop) {
nextHeader = header;
} else {
previousHeader = currentHeader;
currentHeader = header;
}
}
// Reset transforms for header views
header.transform = CGAffineTransformIdentity;
header.layer.zPosition = ZINDEX_DEFAULT;
}];
// If no docked header, bail out
if (!currentHeader) {
return;
}
// Adjust current header to hug the top of the screen
CGFloat currentFrameHeight = currentHeader.bounds.size.height;
CGFloat currentFrameTop = currentHeader.center.y - currentFrameHeight * currentHeader.layer.anchorPoint.y;
CGFloat yOffset = scrollTop - currentFrameTop;
if (nextHeader) {
// The next header nudges the current header out of the way when it reaches
// the top of the screen
CGFloat nextFrameHeight = nextHeader.bounds.size.height;
CGFloat nextFrameTop = nextHeader.center.y - nextFrameHeight * nextHeader.layer.anchorPoint.y;
CGFloat overlap = currentFrameHeight - (nextFrameTop - scrollTop);
yOffset -= MAX(0, overlap);
}
currentHeader.transform = CGAffineTransformMakeTranslation(0, yOffset);
currentHeader.layer.zPosition = ZINDEX_STICKY_HEADER;
if (previousHeader) {
// The previous header sits right above the currentHeader's initial position
// so it scrolls away nicely once the currentHeader has locked into place
CGFloat previousFrameHeight = previousHeader.bounds.size.height;
CGFloat targetCenter = currentFrameTop - previousFrameHeight * (1.0 - previousHeader.layer.anchorPoint.y);
yOffset = targetCenter - previousHeader.center.y;
previousHeader.transform = CGAffineTransformMakeTranslation(0, yOffset);
previousHeader.layer.zPosition = ZINDEX_STICKY_HEADER;
}
}
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
__block UIView *stickyHeader;
[_stickyHeaderIndices enumerateIndexesWithOptions:0 usingBlock:^(NSUInteger idx, BOOL *stop) {
stickyHeader = [self contentView].reactSubviews[idx];
CGPoint convertedPoint = [stickyHeader convertPoint:point fromView:self];
if ([stickyHeader hitTest:convertedPoint withEvent:event]) {
*stop = YES;
} else {
stickyHeader = nil;
}
}];
return stickyHeader ?: [super hitTest:point withEvent:event];
}
@end
@implementation RCTScrollView
{
RCTEventDispatcher *_eventDispatcher;
RCTCustomScrollView *_scrollView;
UIView *_contentView;
NSTimeInterval _lastScrollDispatchTime;
NSMutableArray *_cachedChildFrames;
BOOL _allowNextScrollNoMatterWhat;
}
@synthesize nativeMainScrollDelegate = _nativeMainScrollDelegate;
- (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher
{
RCTAssertParam(eventDispatcher);
if ((self = [super initWithFrame:CGRectZero])) {
_eventDispatcher = eventDispatcher;
_scrollView = [[RCTCustomScrollView alloc] initWithFrame:CGRectZero];
_scrollView.delegate = self;
_scrollView.delaysContentTouches = NO;
_automaticallyAdjustContentInsets = YES;
_contentInset = UIEdgeInsetsZero;
_contentSize = CGSizeZero;
_scrollEventThrottle = 0.0;
_lastScrollDispatchTime = CACurrentMediaTime();
_cachedChildFrames = [[NSMutableArray alloc] init];
[self addSubview:_scrollView];
}
return self;
}
RCT_NOT_IMPLEMENTED(-initWithFrame:(CGRect)frame)
RCT_NOT_IMPLEMENTED(-initWithCoder:(NSCoder *)aDecoder)
- (void)setRemoveClippedSubviews:(__unused BOOL)removeClippedSubviews
{
// Does nothing
}
- (void)insertReactSubview:(UIView *)view atIndex:(__unused NSInteger)atIndex
{
RCTAssert(_contentView == nil, @"RCTScrollView may only contain a single subview");
_contentView = view;
[_scrollView addSubview:view];
}
- (void)removeReactSubview:(UIView *)subview
{
RCTAssert(_contentView == subview, @"Attempted to remove non-existent subview");
_contentView = nil;
[subview removeFromSuperview];
}
- (NSArray *)reactSubviews
{
return _contentView ? @[_contentView] : @[];
}
- (BOOL)centerContent
{
return _scrollView.centerContent;
}
- (void)setCenterContent:(BOOL)centerContent
{
_scrollView.centerContent = centerContent;
}
- (NSIndexSet *)stickyHeaderIndices
{
return _scrollView.stickyHeaderIndices;
}
- (void)setStickyHeaderIndices:(NSIndexSet *)headerIndices
{
RCTAssert(_scrollView.contentSize.width <= self.frame.size.width,
@"sticky headers are not supported with horizontal scrolled views");
_scrollView.stickyHeaderIndices = headerIndices;
}
- (void)setClipsToBounds:(BOOL)clipsToBounds
{
[super setClipsToBounds:clipsToBounds];
[_scrollView setClipsToBounds:clipsToBounds];
}
- (void)dealloc
{
_scrollView.delegate = nil;
}
- (void)layoutSubviews
{
[super layoutSubviews];
RCTAssert(self.subviews.count == 1, @"we should only have exactly one subview");
RCTAssert([self.subviews lastObject] == _scrollView, @"our only subview should be a scrollview");
_scrollView.frame = self.bounds;
[RCTView autoAdjustInsetsForView:self
withScrollView:_scrollView
updateOffset:YES];
[self updateClippedSubviews];
}
- (void)setContentInset:(UIEdgeInsets)contentInset
{
CGPoint contentOffset = _scrollView.contentOffset;
_contentInset = contentInset;
[RCTView autoAdjustInsetsForView:self
withScrollView:_scrollView
updateOffset:NO];
_scrollView.contentOffset = contentOffset;
}
- (void)scrollToOffset:(CGPoint)offset
{
[self scrollToOffset:offset animated:YES];
}
- (void)scrollToOffset:(CGPoint)offset animated:(BOOL)animated
{
if (!CGPointEqualToPoint(_scrollView.contentOffset, offset)) {
[_scrollView setContentOffset:offset animated:animated];
}
}
- (void)zoomToRect:(CGRect)rect animated:(BOOL)animated
{
[_scrollView zoomToRect:rect animated:animated];
}
#pragma mark - ScrollView delegate
#define RCT_SCROLL_EVENT_HANDLER(delegateMethod, eventName) \
- (void)delegateMethod:(UIScrollView *)scrollView \
{ \
[_eventDispatcher sendScrollEventWithType:eventName reactTag:self.reactTag scrollView:scrollView userData:nil]; \
if ([_nativeMainScrollDelegate respondsToSelector:_cmd]) { \
[_nativeMainScrollDelegate delegateMethod:scrollView]; \
} \
}
#define RCT_FORWARD_SCROLL_EVENT(call) \
if ([_nativeMainScrollDelegate respondsToSelector:_cmd]) { \
[_nativeMainScrollDelegate call]; \
}
RCT_SCROLL_EVENT_HANDLER(scrollViewDidEndScrollingAnimation, RCTScrollEventTypeEndDeceleration)
RCT_SCROLL_EVENT_HANDLER(scrollViewWillBeginDecelerating, RCTScrollEventTypeStartDeceleration)
RCT_SCROLL_EVENT_HANDLER(scrollViewDidEndDecelerating, RCTScrollEventTypeEndDeceleration)
RCT_SCROLL_EVENT_HANDLER(scrollViewDidZoom, RCTScrollEventTypeMove)
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
[_scrollView dockClosestSectionHeader];
[self updateClippedSubviews];
NSTimeInterval now = CACurrentMediaTime();
/**
* TODO: this logic looks wrong, and it may be because it is. Currently, if _scrollEventThrottle
* is set to zero (the default), the "didScroll" event is only sent once per scroll, instead of repeatedly
* while scrolling as expected. However, if you "fix" that bug, ScrollView will generate repeated
* warnings, and behave strangely (ListView works fine however), so don't fix it unless you fix that too!
*/
if (_allowNextScrollNoMatterWhat ||
(_scrollEventThrottle > 0 && _scrollEventThrottle < (now - _lastScrollDispatchTime))) {
// Calculate changed frames
NSMutableArray *updatedChildFrames = [[NSMutableArray alloc] init];
[[_contentView reactSubviews] enumerateObjectsUsingBlock:
^(UIView *subview, NSUInteger idx, __unused BOOL *stop) {
// Check if new or changed
CGRect newFrame = subview.frame;
BOOL frameChanged = NO;
if (_cachedChildFrames.count <= idx) {
frameChanged = YES;
[_cachedChildFrames addObject:[NSValue valueWithCGRect:newFrame]];
} else if (!CGRectEqualToRect(newFrame, [_cachedChildFrames[idx] CGRectValue])) {
frameChanged = YES;
_cachedChildFrames[idx] = [NSValue valueWithCGRect:newFrame];
}
// Create JS frame object
if (frameChanged) {
[updatedChildFrames addObject: @{
@"index": @(idx),
@"x": @(newFrame.origin.x),
@"y": @(newFrame.origin.y),
@"width": @(newFrame.size.width),
@"height": @(newFrame.size.height),
}];
}
}];
// If there are new frames, add them to event data
NSDictionary *userData = nil;
if (updatedChildFrames.count > 0) {
userData = @{@"updatedChildFrames": updatedChildFrames};
}
// Dispatch event
[_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeMove
reactTag:self.reactTag
scrollView:scrollView
userData:userData];
// Update dispatch time
_lastScrollDispatchTime = now;
_allowNextScrollNoMatterWhat = NO;
}
RCT_FORWARD_SCROLL_EVENT(scrollViewDidScroll:scrollView);
}
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
_allowNextScrollNoMatterWhat = YES; // Ensure next scroll event is recorded, regardless of throttle
[_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeStart reactTag:self.reactTag scrollView:scrollView userData:nil];
RCT_FORWARD_SCROLL_EVENT(scrollViewWillBeginDragging:scrollView);
}
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
NSDictionary *userData = @{
@"velocity": @{
@"x": @(velocity.x),
@"y": @(velocity.y)
},
@"targetContentOffset": @{
@"x": @(targetContentOffset->x),
@"y": @(targetContentOffset->y)
}
};
[_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeEnd reactTag:self.reactTag scrollView:scrollView userData:userData];
RCT_FORWARD_SCROLL_EVENT(scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset);
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
RCT_FORWARD_SCROLL_EVENT(scrollViewDidEndDragging:scrollView willDecelerate:decelerate);
}
- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(UIView *)view
{
[_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeStart reactTag:self.reactTag scrollView:scrollView userData:nil];
RCT_FORWARD_SCROLL_EVENT(scrollViewWillBeginZooming:scrollView withView:view);
}
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
[_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeEnd reactTag:self.reactTag scrollView:scrollView userData:nil];
RCT_FORWARD_SCROLL_EVENT(scrollViewDidEndZooming:scrollView withView:view atScale:scale);
}
- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView
{
if ([_nativeMainScrollDelegate respondsToSelector:_cmd]) {
return [_nativeMainScrollDelegate scrollViewShouldScrollToTop:scrollView];
}
return YES;
}
- (UIView *)viewForZoomingInScrollView:(__unused UIScrollView *)scrollView
{
return _contentView;
}
#pragma mark - Setters
- (CGSize)_calculateViewportSize
{
CGSize viewportSize = self.bounds.size;
if (_automaticallyAdjustContentInsets) {
UIEdgeInsets contentInsets = [RCTView contentInsetsForView:self];
viewportSize = CGSizeMake(self.bounds.size.width - contentInsets.left - contentInsets.right,
self.bounds.size.height - contentInsets.top - contentInsets.bottom);
}
return viewportSize;
}
- (CGPoint)calculateOffsetForContentSize:(CGSize)newContentSize
{
CGPoint oldOffset = _scrollView.contentOffset;
CGPoint newOffset = oldOffset;
CGSize oldContentSize = _scrollView.contentSize;
CGSize viewportSize = [self _calculateViewportSize];
BOOL fitsinViewportY = oldContentSize.height <= viewportSize.height && newContentSize.height <= viewportSize.height;
if (newContentSize.height < oldContentSize.height && !fitsinViewportY) {
CGFloat offsetHeight = oldOffset.y + viewportSize.height;
if (oldOffset.y < 0) {
// overscrolled on top, leave offset alone
} else if (offsetHeight > oldContentSize.height) {
// overscrolled on the bottom, preserve overscroll amount
newOffset.y = MAX(0, oldOffset.y - (oldContentSize.height - newContentSize.height));
} else if (offsetHeight > newContentSize.height) {
// offset falls outside of bounds, scroll back to end of list
newOffset.y = MAX(0, newContentSize.height - viewportSize.height);
}
}
BOOL fitsinViewportX = oldContentSize.width <= viewportSize.width && newContentSize.width <= viewportSize.width;
if (newContentSize.width < oldContentSize.width && !fitsinViewportX) {
CGFloat offsetHeight = oldOffset.x + viewportSize.width;
if (oldOffset.x < 0) {
// overscrolled at the beginning, leave offset alone
} else if (offsetHeight > oldContentSize.width && newContentSize.width > viewportSize.width) {
// overscrolled at the end, preserve overscroll amount as much as possible
newOffset.x = MAX(0, oldOffset.x - (oldContentSize.width - newContentSize.width));
} else if (offsetHeight > newContentSize.width) {
// offset falls outside of bounds, scroll back to end
newOffset.x = MAX(0, newContentSize.width - viewportSize.width);
}
}
// all other cases, offset doesn't change
return newOffset;
}
/**
* Once you set the `contentSize`, to a nonzero value, it is assumed to be
* managed by you, and we'll never automatically compute the size for you,
* unless you manually reset it back to {0, 0}
*/
- (CGSize)contentSize
{
if (!CGSizeEqualToSize(_contentSize, CGSizeZero)) {
return _contentSize;
} else if (!_contentView) {
return CGSizeZero;
} else {
CGSize singleSubviewSize = _contentView.frame.size;
CGPoint singleSubviewPosition = _contentView.frame.origin;
return (CGSize){
singleSubviewSize.width + singleSubviewPosition.x,
singleSubviewSize.height + singleSubviewPosition.y
};
}
}
- (void)reactBridgeDidFinishTransaction
{
CGSize contentSize = self.contentSize;
if (!CGSizeEqualToSize(_scrollView.contentSize, contentSize)) {
// When contentSize is set manually, ScrollView internals will reset
// contentOffset to {0, 0}. Since we potentially set contentSize whenever
// anything in the ScrollView updates, we workaround this issue by manually
// adjusting contentOffset whenever this happens
CGPoint newOffset = [self calculateOffsetForContentSize:contentSize];
_scrollView.contentSize = contentSize;
_scrollView.contentOffset = newOffset;
}
[_scrollView dockClosestSectionHeader];
}
// Note: setting several properties of UIScrollView has the effect of
// resetting its contentOffset to {0, 0}. To prevent this, we generate
// setters here that will record the contentOffset beforehand, and
// restore it after the property has been set.
#define RCT_SET_AND_PRESERVE_OFFSET(setter, type) \
- (void)setter:(type)value \
{ \
CGPoint contentOffset = _scrollView.contentOffset; \
[_scrollView setter:value]; \
_scrollView.contentOffset = contentOffset; \
}
RCT_SET_AND_PRESERVE_OFFSET(setAlwaysBounceHorizontal, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setAlwaysBounceVertical, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setBounces, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setBouncesZoom, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setCanCancelContentTouches, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setDecelerationRate, CGFloat)
RCT_SET_AND_PRESERVE_OFFSET(setDirectionalLockEnabled, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setKeyboardDismissMode, UIScrollViewKeyboardDismissMode)
RCT_SET_AND_PRESERVE_OFFSET(setMaximumZoomScale, CGFloat)
RCT_SET_AND_PRESERVE_OFFSET(setMinimumZoomScale, CGFloat)
RCT_SET_AND_PRESERVE_OFFSET(setPagingEnabled, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setScrollEnabled, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setScrollsToTop, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setShowsHorizontalScrollIndicator, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setShowsVerticalScrollIndicator, BOOL)
RCT_SET_AND_PRESERVE_OFFSET(setZoomScale, CGFloat);
RCT_SET_AND_PRESERVE_OFFSET(setScrollIndicatorInsets, UIEdgeInsets);
#pragma mark - Forward methods and properties to underlying UIScrollView
- (BOOL)respondsToSelector:(SEL)aSelector
{
return [super respondsToSelector:aSelector] || [_scrollView respondsToSelector:aSelector];
}
- (void)setValue:(id)value forUndefinedKey:(NSString *)key
{
[_scrollView setValue:value forKey:key];
}
- (id)valueForUndefinedKey:(NSString *)key
{
return [_scrollView valueForKey:key];
}
@end
@implementation RCTEventDispatcher (RCTScrollView)
- (void)sendScrollEventWithType:(RCTScrollEventType)type
reactTag:(NSNumber *)reactTag
scrollView:(UIScrollView *)scrollView
userData:(NSDictionary *)userData
{
RCTScrollEvent *scrollEvent = [[RCTScrollEvent alloc] initWithType:type
reactTag:reactTag
scrollView:scrollView
userData:userData];
[self sendEvent:scrollEvent];
}
@end
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