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Update ASRangeController to support ASCollectionView and no longer assume vertical scrolling when calculates working range.

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This commit is contained in:
Huy Nguyen 2014-11-12 08:14:27 +02:00
parent a3bc21f29f
commit 0eb7e5fc39
1 changed files with 22 additions and 18 deletions
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40
AsyncDisplayKit/Details/ASRangeController.mm
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@ -14,8 +14,8 @@
#import "ASRangeControllerInternal.h"
typedef NS_ENUM(NSInteger, ASScrollDirection) {
ASScrollDirectionUp,
ASScrollDirectionDown,
ASScrollDirectionBackward,
ASScrollDirectionForward,
};
@interface ASRangeController () {
@ -283,7 +283,7 @@ static BOOL ASRangeIsValid(NSRange range)
_visibleRange = _workingRange = NSMakeRange(NSNotFound, 0);
_sizedNodeCount = 0;
_nodeSizes = [NSMutableArray array];
_scrollDirection = ASScrollDirectionDown;
_scrollDirection = ASScrollDirectionForward;
_workingIndexPaths = [NSMutableOrderedSet orderedSet];
// don't bother sizing if the data source is empty
@ -413,34 +413,38 @@ static NSRange ASCalculateWorkingRange(ASRangeTuningParameters params, ASScrollD
ASDisplayNodeCAssert(NSMaxRange(visibleRange) <= nodeSizes.count, @"nodes can't be visible until they're sized");
// extend the visible range by enough nodes to fill at least the requested number of screenfuls
// NB. this logic assumes (UITableView-style) vertical scrolling and would need to be changed for ASCollectionView
// NB. this logic assumes there is no overlap between nodes. It also doesn't
// take spacing between nodes into account.
CGFloat viewportArea = viewport.width * viewport.height;
CGFloat minUpperBufferSize, minLowerBufferSize;
switch (scrollDirection) {
case ASScrollDirectionUp:
minUpperBufferSize = viewport.height * params.leadingBufferScreenfuls;
minLowerBufferSize = viewport.height * params.trailingBufferScreenfuls;
case ASScrollDirectionBackward:
minUpperBufferSize = viewportArea * params.leadingBufferScreenfuls;
minLowerBufferSize = viewportArea * params.trailingBufferScreenfuls;
break;
case ASScrollDirectionDown:
minUpperBufferSize = viewport.height * params.trailingBufferScreenfuls;
minLowerBufferSize = viewport.height * params.leadingBufferScreenfuls;
case ASScrollDirectionForward:
minUpperBufferSize = viewportArea * params.trailingBufferScreenfuls;
minLowerBufferSize = viewportArea * params.leadingBufferScreenfuls;
break;
}
// "top" buffer (above the screen, if we're scrolling vertically)
NSInteger upperBuffer = 0;
CGFloat upperBufferHeight = 0.0f;
for (NSInteger idx = visibleRange.location - 1; idx >= 0 && upperBufferHeight < minUpperBufferSize; idx--) {
CGFloat upperBufferArea = 0.0f;
for (NSInteger idx = visibleRange.location - 1; idx >= 0 && upperBufferArea < minUpperBufferSize; idx--) {
upperBuffer++;
upperBufferHeight += [nodeSizes[idx] CGSizeValue].height;
CGSize nodeSize = [nodeSizes[idx] CGSizeValue];
upperBufferArea += nodeSize.width * nodeSize.height;
}
// "bottom" buffer (below the screen, if we're scrolling vertically)
NSInteger lowerBuffer = 0;
CGFloat lowerBufferHeight = 0.0f;
for (NSInteger idx = NSMaxRange(visibleRange); idx < nodeSizes.count && lowerBufferHeight < minLowerBufferSize; idx++) {
CGFloat lowerBufferArea = 0.0f;
for (NSInteger idx = NSMaxRange(visibleRange); idx < nodeSizes.count && lowerBufferArea < minLowerBufferSize; idx++) {
lowerBuffer++;
lowerBufferHeight += [nodeSizes[idx] CGSizeValue].height;
CGSize nodeSize = [nodeSizes[idx] CGSizeValue];
lowerBufferArea += nodeSize.width * nodeSize.height;
}
return NSMakeRange(visibleRange.location - upperBuffer,
@ -459,9 +463,9 @@ static NSRange ASCalculateWorkingRange(ASRangeTuningParameters params, ASScrollD
// figure out where we're going, because that's where the bulk of the working range needs to be
NSInteger scrollDelta = _visibleRange.location - previouslyVisible.location;
if (scrollDelta < 0)
_scrollDirection = ASScrollDirectionUp;
_scrollDirection = ASScrollDirectionBackward;
if (scrollDelta > 0)
_scrollDirection = ASScrollDirectionDown;
_scrollDirection = ASScrollDirectionForward;
[self recalculateWorkingRange];
}