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Merge pull request #1477 from maicki/SmallContentBatchFetch

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[ASBatchContext] Fix fetch call won't occur for content smaller than bounds unless user scrolls
This commit is contained in:
appleguy
2016-04-09 19:15:06 -07:00
parent e9b5b9ba78 e9fe92444f
commit 7c4db3fbc1
5 changed files with 241 additions and 121 deletions
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124
AsyncDisplayKit/ASCollectionView.mm
View File

@@ -91,7 +91,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
#pragma mark -
#pragma mark ASCollectionView.
@interface ASCollectionView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor> {
@interface ASCollectionView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor, ASBatchFetchingScrollView> {
ASCollectionViewProxy *_proxyDataSource;
ASCollectionViewProxy *_proxyDelegate;
@@ -605,8 +605,45 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
cellNode.scrollView = nil;
}
#pragma mark -
#pragma mark Scroll Direction.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
// If a scroll happenes the current range mode needs to go to full
ASInterfaceState interfaceState = [self interfaceStateForRangeController:_rangeController];
if (ASInterfaceStateIncludesVisible(interfaceState)) {
[_rangeController updateCurrentRangeWithMode:ASLayoutRangeModeFull];
}
for (_ASCollectionViewCell *collectionCell in _cellsForVisibilityUpdates) {
// Only nodes that respond to the selector are added to _cellsForVisibilityUpdates
[[collectionCell node] cellNodeVisibilityEvent:ASCellNodeVisibilityEventVisibleRectChanged
inScrollView:scrollView
withCellFrame:collectionCell.frame];
}
if (_asyncDelegateImplementsScrollviewDidScroll) {
[_asyncDelegate scrollViewDidScroll:scrollView];
}
}
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
_deceleratingVelocity = CGPointMake(
scrollView.contentOffset.x - ((targetContentOffset != NULL) ? targetContentOffset->x : 0),
scrollView.contentOffset.y - ((targetContentOffset != NULL) ? targetContentOffset->y : 0)
);
if (targetContentOffset != NULL) {
ASDisplayNodeAssert(_batchContext != nil, @"Batch context should exist");
[self _beginBatchFetchingIfNeededWithScrollView:self forScrollDirection:[self scrollDirection] contentOffset:*targetContentOffset];
}
if ([_asyncDelegate respondsToSelector:@selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)]) {
[_asyncDelegate scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];
}
}
#pragma mark - Scroll Direction.
- (ASScrollDirection)scrollDirection
{
@@ -700,45 +737,14 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
}
#pragma mark -
#pragma mark Batch Fetching
#pragma mark - Batch Fetching
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
- (ASBatchContext *)batchContext
{
_deceleratingVelocity = CGPointMake(
scrollView.contentOffset.x - ((targetContentOffset != NULL) ? targetContentOffset->x : 0),
scrollView.contentOffset.y - ((targetContentOffset != NULL) ? targetContentOffset->y : 0)
);
if (targetContentOffset != NULL) {
[self handleBatchFetchScrollingToOffset:*targetContentOffset];
}
if ([_asyncDelegate respondsToSelector:@selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)]) {
[_asyncDelegate scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset];
}
return _batchContext;
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
// If a scroll happenes the current range mode needs to go to full
ASInterfaceState interfaceState = [self interfaceStateForRangeController:_rangeController];
if (ASInterfaceStateIncludesVisible(interfaceState)) {
[_rangeController updateCurrentRangeWithMode:ASLayoutRangeModeFull];
}
for (_ASCollectionViewCell *collectionCell in _cellsForVisibilityUpdates) {
// Only nodes that respond to the selector are added to _cellsForVisibilityUpdates
[[collectionCell node] cellNodeVisibilityEvent:ASCellNodeVisibilityEventVisibleRectChanged
inScrollView:scrollView
withCellFrame:collectionCell.frame];
}
if (_asyncDelegateImplementsScrollviewDidScroll) {
[_asyncDelegate scrollViewDidScroll:scrollView];
}
}
- (BOOL)shouldBatchFetch
- (BOOL)canBatchFetch
{
// if the delegate does not respond to this method, there is no point in starting to fetch
BOOL canFetch = [_asyncDelegate respondsToSelector:@selector(collectionView:willBeginBatchFetchWithContext:)];
@@ -749,16 +755,37 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
}
}
- (void)handleBatchFetchScrollingToOffset:(CGPoint)targetOffset
- (void)_scheduleCheckForBatchFetching
{
ASDisplayNodeAssert(_batchContext != nil, @"Batch context should exist");
if (![self shouldBatchFetch]) {
// Push this to the next runloop to be sure the scroll view has the right content size
dispatch_async(dispatch_get_main_queue(), ^{
[self _checkForBatchFetching];
});
}
- (void)_checkForBatchFetching
{
// Dragging will be handled in scrollViewWillEndDragging:withVelocity:targetContentOffset:
if (self.isDragging || self.isTracking) {
return;
}
if (ASDisplayShouldFetchBatchForContext(_batchContext, [self scrollDirection], self.bounds, self.contentSize, targetOffset, _leadingScreensForBatching)) {
[_batchContext beginBatchFetching];
[self _beginBatchFetchingIfNeededWithScrollView:self forScrollDirection:[self scrollableDirections] contentOffset:self.contentOffset];
}
- (void)_beginBatchFetchingIfNeededWithScrollView:(UIScrollView<ASBatchFetchingScrollView> *)scrollView forScrollDirection:(ASScrollDirection)scrollDirection contentOffset:(CGPoint)contentOffset
{
if (ASDisplayShouldFetchBatchForScrollView(self, scrollDirection, contentOffset)) {
[self _beginBatchFetching];
}
}
- (void)_beginBatchFetching
{
NSLog(@"begin batch fetching");
[_batchContext beginBatchFetching];
if ([_asyncDelegate respondsToSelector:@selector(collectionView:willBeginBatchFetchWithContext:)]) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[_asyncDelegate collectionView:self willBeginBatchFetchWithContext:_batchContext];
});
@@ -954,7 +981,10 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
for (dispatch_block_t block in _batchUpdateBlocks) {
block();
}
} completion:completion];
} completion:^(BOOL finished){
[self _scheduleCheckForBatchFetching];
if (completion) { completion(finished); }
}];
});
[_batchUpdateBlocks removeAllObjects];
@@ -977,6 +1007,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
[_layoutFacilitator collectionViewWillEditCellsAtIndexPaths:indexPaths batched:NO];
[UIView performWithoutAnimation:^{
[super insertItemsAtIndexPaths:indexPaths];
[self _scheduleCheckForBatchFetching];
}];
}
}
@@ -997,6 +1028,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
[_layoutFacilitator collectionViewWillEditCellsAtIndexPaths:indexPaths batched:NO];
[UIView performWithoutAnimation:^{
[super deleteItemsAtIndexPaths:indexPaths];
[self _scheduleCheckForBatchFetching];
}];
}
}
@@ -1017,6 +1049,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
[_layoutFacilitator collectionViewWillEditSectionsAtIndexSet:indexSet batched:NO];
[UIView performWithoutAnimation:^{
[super insertSections:indexSet];
[self _scheduleCheckForBatchFetching];
}];
}
}
@@ -1037,6 +1070,7 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
[_layoutFacilitator collectionViewWillEditSectionsAtIndexSet:indexSet batched:NO];
[UIView performWithoutAnimation:^{
[super deleteSections:indexSet];
[self _scheduleCheckForBatchFetching];
}];
}
}

167
AsyncDisplayKit/ASTableView.mm
View File

@@ -88,9 +88,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
- (instancetype)_initWithTableView:(ASTableView *)tableView;
@end
@interface ASTableView () <ASRangeControllerDataSource, ASRangeControllerDelegate,
ASDataControllerSource, _ASTableViewCellDelegate,
ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor>
@interface ASTableView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, _ASTableViewCellDelegate, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor, ASBatchFetchingScrollView>
{
ASTableViewProxy *_proxyDataSource;
ASTableViewProxy *_proxyDelegate;
@@ -524,8 +522,8 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
}
}
#pragma mark -
#pragma mark Intercepted selectors
#pragma mark - Intercepted selectors
- (void)setTableHeaderView:(UIView *)tableHeaderView
{
@@ -579,47 +577,6 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
return [_dataController numberOfRowsInSection:section];
}
- (ASScrollDirection)scrollDirection
{
CGPoint scrollVelocity;
if (self.isTracking) {
scrollVelocity = [self.panGestureRecognizer velocityInView:self.superview];
} else {
scrollVelocity = _deceleratingVelocity;
}
ASScrollDirection scrollDirection = [self _scrollDirectionForVelocity:scrollVelocity];
return ASScrollDirectionApplyTransform(scrollDirection, self.transform);
}
- (ASScrollDirection)_scrollDirectionForVelocity:(CGPoint)velocity
{
ASScrollDirection direction = ASScrollDirectionNone;
if (velocity.y < 0.0) {
direction = ASScrollDirectionDown;
} else if (velocity.y > 0.0) {
direction = ASScrollDirectionUp;
}
return direction;
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
// If a scroll happenes the current range mode needs to go to full
ASInterfaceState interfaceState = [self interfaceStateForRangeController:_rangeController];
if (ASInterfaceStateIncludesVisible(interfaceState)) {
[_rangeController updateCurrentRangeWithMode:ASLayoutRangeModeFull];
}
for (_ASTableViewCell *tableCell in _cellsForVisibilityUpdates) {
[[tableCell node] cellNodeVisibilityEvent:ASCellNodeVisibilityEventVisibleRectChanged
inScrollView:scrollView
withCellFrame:tableCell.frame];
}
if (_asyncDelegateImplementsScrollviewDidScroll) {
[_asyncDelegate scrollViewDidScroll:scrollView];
}
}
- (void)tableView:(UITableView *)tableView willDisplayCell:(_ASTableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
_pendingVisibleIndexPath = indexPath;
@@ -631,7 +588,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
[_asyncDelegate tableView:self willDisplayNodeForRowAtIndexPath:indexPath];
}
[_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
[_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:[self scrollDirection]];
if (cellNode.neverShowPlaceholders) {
[cellNode recursivelyEnsureDisplaySynchronously:YES];
@@ -650,7 +607,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
ASCellNode *cellNode = [cell node];
[_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
[_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:[self scrollDirection]];
if ([_asyncDelegate respondsToSelector:@selector(tableView:didEndDisplayingNode:forRowAtIndexPath:)]) {
ASDisplayNodeAssertNotNil(cellNode, @"Expected node associated with removed cell not to be nil.");
@@ -672,8 +629,23 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
}
#pragma mark -
#pragma mark Batch Fetching
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
// If a scroll happenes the current range mode needs to go to full
ASInterfaceState interfaceState = [self interfaceStateForRangeController:_rangeController];
if (ASInterfaceStateIncludesVisible(interfaceState)) {
[_rangeController updateCurrentRangeWithMode:ASLayoutRangeModeFull];
}
for (_ASTableViewCell *tableCell in _cellsForVisibilityUpdates) {
[[tableCell node] cellNodeVisibilityEvent:ASCellNodeVisibilityEventVisibleRectChanged
inScrollView:scrollView
withCellFrame:tableCell.frame];
}
if (_asyncDelegateImplementsScrollviewDidScroll) {
[_asyncDelegate scrollViewDidScroll:scrollView];
}
}
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
@@ -683,7 +655,8 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
);
if (targetContentOffset != NULL) {
[self handleBatchFetchScrollingToOffset:*targetContentOffset];
ASDisplayNodeAssert(_batchContext != nil, @"Batch context should exist");
[self _beginBatchFetchingIfNeededWithScrollView:self forScrollDirection:[self scrollDirection] contentOffset:*targetContentOffset];
}
if ([_asyncDelegate respondsToSelector:@selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)]) {
@@ -691,7 +664,62 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
}
}
- (BOOL)shouldBatchFetch
#pragma mark - Scroll Direction
- (ASScrollDirection)scrollDirection
{
CGPoint scrollVelocity;
if (self.isTracking) {
scrollVelocity = [self.panGestureRecognizer velocityInView:self.superview];
} else {
scrollVelocity = _deceleratingVelocity;
}
ASScrollDirection scrollDirection = [self _scrollDirectionForVelocity:scrollVelocity];
return ASScrollDirectionApplyTransform(scrollDirection, self.transform);
}
- (ASScrollDirection)_scrollDirectionForVelocity:(CGPoint)scrollVelocity
{
ASScrollDirection direction = ASScrollDirectionNone;
ASScrollDirection scrollableDirections = [self scrollableDirections];
if (ASScrollDirectionContainsVerticalDirection(scrollableDirections)) { // Can scroll vertically.
if (scrollVelocity.y < 0.0) {
direction |= ASScrollDirectionDown;
} else if (scrollVelocity.y > 0.0) {
direction |= ASScrollDirectionUp;
}
}
return direction;
}
- (ASScrollDirection)scrollableDirections
{
ASScrollDirection scrollableDirection = ASScrollDirectionNone;
CGFloat totalContentWidth = self.contentSize.width + self.contentInset.left + self.contentInset.right;
CGFloat totalContentHeight = self.contentSize.height + self.contentInset.top + self.contentInset.bottom;
if (self.alwaysBounceHorizontal || totalContentWidth > self.bounds.size.width) { // Can scroll horizontally.
scrollableDirection |= ASScrollDirectionHorizontalDirections;
}
if (self.alwaysBounceVertical || totalContentHeight > self.bounds.size.height) { // Can scroll vertically.
scrollableDirection |= ASScrollDirectionVerticalDirections;
}
return scrollableDirection;
}
#pragma mark - Batch Fetching
- (ASBatchContext *)batchContext
{
return _batchContext;
}
- (BOOL)canBatchFetch
{
// if the delegate does not respond to this method, there is no point in starting to fetch
BOOL canFetch = [_asyncDelegate respondsToSelector:@selector(tableView:willBeginBatchFetchWithContext:)];
@@ -702,16 +730,35 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
}
}
- (void)handleBatchFetchScrollingToOffset:(CGPoint)targetOffset
- (void)_scheduleCheckForBatchFetching
{
ASDisplayNodeAssert(_batchContext != nil, @"Batch context should exist");
// Push this to the next runloop to be sure the scroll view has the right content size
dispatch_async(dispatch_get_main_queue(), ^{
[self _checkForBatchFetching];
});
}
if (![self shouldBatchFetch]) {
- (void)_checkForBatchFetching
{
// Dragging will be handled in scrollViewWillEndDragging:withVelocity:targetContentOffset:
if (self.isDragging || self.isTracking) {
return;
}
[self _beginBatchFetchingIfNeededWithScrollView:self forScrollDirection:[self scrollableDirections] contentOffset:self.contentOffset];
}
if (ASDisplayShouldFetchBatchForContext(_batchContext, [self scrollDirection], self.bounds, self.contentSize, targetOffset, _leadingScreensForBatching)) {
[_batchContext beginBatchFetching];
- (void)_beginBatchFetchingIfNeededWithScrollView:(UIScrollView<ASBatchFetchingScrollView> *)scrollView forScrollDirection:(ASScrollDirection)scrollDirection contentOffset:(CGPoint)contentOffset
{
if (ASDisplayShouldFetchBatchForScrollView(self, scrollDirection, contentOffset)) {
[self _beginBatchFetching];
}
}
- (void)_beginBatchFetching
{
[_batchContext beginBatchFetching];
if ([_asyncDelegate respondsToSelector:@selector(tableView:willBeginBatchFetchWithContext:)]) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[_asyncDelegate tableView:self willBeginBatchFetchWithContext:_batchContext];
});
@@ -857,6 +904,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
BOOL preventAnimation = animationOptions == UITableViewRowAnimationNone;
ASPerformBlockWithoutAnimation(preventAnimation, ^{
[super insertRowsAtIndexPaths:indexPaths withRowAnimation:(UITableViewRowAnimation)animationOptions];
[self _scheduleCheckForBatchFetching];
});
if (_automaticallyAdjustsContentOffset) {
@@ -876,6 +924,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
BOOL preventAnimation = animationOptions == UITableViewRowAnimationNone;
ASPerformBlockWithoutAnimation(preventAnimation, ^{
[super deleteRowsAtIndexPaths:indexPaths withRowAnimation:(UITableViewRowAnimation)animationOptions];
[self _scheduleCheckForBatchFetching];
});
if (_automaticallyAdjustsContentOffset) {
@@ -896,6 +945,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
BOOL preventAnimation = animationOptions == UITableViewRowAnimationNone;
ASPerformBlockWithoutAnimation(preventAnimation, ^{
[super insertSections:indexSet withRowAnimation:(UITableViewRowAnimation)animationOptions];
[self _scheduleCheckForBatchFetching];
});
}
@@ -911,6 +961,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
BOOL preventAnimation = animationOptions == UITableViewRowAnimationNone;
ASPerformBlockWithoutAnimation(preventAnimation, ^{
[super deleteSections:indexSet withRowAnimation:(UITableViewRowAnimation)animationOptions];
[self _scheduleCheckForBatchFetching];
});
}
@@ -1077,7 +1128,7 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
// Updating the visible node index paths only for not range managed nodes. Range managed nodes will get their
// their update in the layout pass
if (![node supportsRangeManagedInterfaceState]) {
[_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
[_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:[self scrollDirection]];
}
}

12
AsyncDisplayKit/Details/ASBatchContext.mm
View File

@@ -45,6 +45,12 @@ typedef NS_ENUM(NSInteger, ASBatchContextState) {
return _state == ASBatchContextStateCancelled;
}
- (void)beginBatchFetching
{
ASDN::MutexLocker l(_propertyLock);
_state = ASBatchContextStateFetching;
}
- (void)completeBatchFetching:(BOOL)didComplete
{
if (didComplete) {
@@ -53,12 +59,6 @@ typedef NS_ENUM(NSInteger, ASBatchContextState) {
}
}
- (void)beginBatchFetching
{
ASDN::MutexLocker l(_propertyLock);
_state = ASBatchContextStateFetching;
}
- (void)cancelBatchFetching
{
ASDN::MutexLocker l(_propertyLock);

21
AsyncDisplayKit/Private/ASBatchFetching.h
View File

@@ -10,10 +10,29 @@
#import "ASBatchContext.h"
#import "ASScrollDirection.h"
#import "ASBaseDefines.h"
ASDISPLAYNODE_EXTERN_C_BEGIN
@protocol ASBatchFetchingScrollView <NSObject>
- (BOOL)canBatchFetch;
- (ASBatchContext *)batchContext;
- (CGFloat)leadingScreensForBatching;
@end
/**
@abstract Determine if batch fetching should begin based on the state of the parameters.
@discussion This method is broken into a category for unit testing purposes and should be used with the ASTableView and
* ASCollectionView batch fetching API.
@param context The scroll view that in-flight fetches are happening.
@param scrollDirection The current scrolling direction of the scroll view.
@param targetOffset The offset that the scrollview will scroll to.
@return Whether or not the current state should proceed with batch fetching.
*/
BOOL ASDisplayShouldFetchBatchForScrollView(UIScrollView<ASBatchFetchingScrollView> *scrollView, ASScrollDirection scrollDirection, CGPoint contentOffset);
/**
@abstract Determine if batch fetching should begin based on the state of the parameters.
@param context The batch fetching context that contains knowledge about in-flight fetches.

38
AsyncDisplayKit/Private/ASBatchFetching.m
View File

@@ -8,34 +8,50 @@
#import "ASBatchFetching.h"
BOOL ASDisplayShouldFetchBatchForScrollView(UIScrollView<ASBatchFetchingScrollView> *scrollView, ASScrollDirection scrollDirection, CGPoint contentOffset)
{
// Don't fetch if the scroll view does not allow
if (![scrollView canBatchFetch]) {
return NO;
}
// Check if we should batch fetch
ASBatchContext *context = scrollView.batchContext;
CGRect bounds = scrollView.bounds;
CGSize contentSize = scrollView.contentSize;
CGFloat leadingScreens = scrollView.leadingScreensForBatching;
return ASDisplayShouldFetchBatchForContext(context, scrollDirection, bounds, contentSize, contentOffset, leadingScreens);
}
BOOL ASDisplayShouldFetchBatchForContext(ASBatchContext *context,
ASScrollDirection scrollDirection,
CGRect bounds,
CGSize contentSize,
CGPoint targetOffset,
CGFloat leadingScreens) {
// do not allow fetching if a batch is already in-flight and hasn't been completed or cancelled
ASScrollDirection scrollDirection,
CGRect bounds,
CGSize contentSize,
CGPoint targetOffset,
CGFloat leadingScreens)
{
// Do not allow fetching if a batch is already in-flight and hasn't been completed or cancelled
if ([context isFetching]) {
return NO;
}
// only Down and Right scrolls are currently supported (tail loading)
if (scrollDirection != ASScrollDirectionDown && scrollDirection != ASScrollDirectionRight) {
// Only Down and Right scrolls are currently supported (tail loading)
if (!ASScrollDirectionContainsDown(scrollDirection) && !ASScrollDirectionContainsRight(scrollDirection)) {
return NO;
}
// no fetching for null states
// No fetching for null states
if (leadingScreens <= 0.0 || CGRectEqualToRect(bounds, CGRectZero)) {
return NO;
}
CGFloat viewLength, offset, contentLength;
if (scrollDirection == ASScrollDirectionDown) {
if (ASScrollDirectionContainsDown(scrollDirection)) {
viewLength = bounds.size.height;
offset = targetOffset.y;
contentLength = contentSize.height;
} else { // horizontal
} else { // horizontal / right
viewLength = bounds.size.width;
offset = targetOffset.x;
contentLength = contentSize.width;