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DMPagingScrollView/DMPagingScrollView/DMPagingScrollView.m
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// The MIT License (MIT) | |
// | |
// Copyright (c) 2013 Darren Mo | |
// | |
// Permission is hereby granted, free of charge, to any person obtaining a copy | |
// of this software and associated documentation files (the "Software"), to deal | |
// in the Software without restriction, including without limitation the rights | |
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
// copies of the Software, and to permit persons to whom the Software is | |
// furnished to do so, subject to the following conditions: | |
// | |
// The above copyright notice and this permission notice shall be included in | |
// all copies or substantial portions of the Software. | |
// | |
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
// THE SOFTWARE. | |
#import "DMPagingScrollView.h" | |
#import <objc/runtime.h> | |
#define DRAG_DISPLACEMENT_THRESHOLD 20 | |
@implementation DMPagingScrollView { | |
// Delegate caching | |
BOOL _delegateRespondsToWillBeginDragging; | |
BOOL _delegateRespondsToWillEndDragging; | |
BOOL _delegateRespondsToDidEndDragging; | |
BOOL _delegateRespondsToDidEndDecelerating; | |
BOOL _delegateRespondsToDidEndScrollingAnimation; | |
BOOL _delegateRespondsToDidEndZooming; | |
// Indicates whether a snapping animation is occurring | |
BOOL _snapping; | |
// Properties of the drag | |
CGPoint _dragVelocity; | |
CGPoint _dragDisplacement; | |
} | |
#pragma mark - Initialization | |
- (id)initWithCoder:(NSCoder *)aDecoder { | |
self = [super initWithCoder:aDecoder]; | |
if (self) { | |
[self performInit]; | |
} | |
return self; | |
} | |
- (id)initWithFrame:(CGRect)frame { | |
self = [super initWithFrame:frame]; | |
if (self) { | |
[self performInit]; | |
} | |
return self; | |
} | |
- (void)performInit { | |
[super setDelegate:self]; | |
if ([super isPagingEnabled]) { | |
[super setPagingEnabled:NO]; | |
_pagingEnabled = YES; | |
} | |
} | |
#pragma mark - Overriding the delegate | |
@synthesize delegate = _actualDelegate; | |
- (void)setDelegate:(id<UIScrollViewDelegate>)delegate { | |
if (delegate == _actualDelegate) | |
return; | |
_actualDelegate = delegate; | |
// Do our own caching | |
_delegateRespondsToWillBeginDragging = [_actualDelegate respondsToSelector:@selector(scrollViewWillBeginDragging:)]; | |
_delegateRespondsToWillEndDragging = [_actualDelegate respondsToSelector:@selector(scrollViewWillEndDragging:withVelocity:targetContentOffset:)]; | |
_delegateRespondsToDidEndDragging = [_actualDelegate respondsToSelector:@selector(scrollViewDidEndDragging:willDecelerate:)]; | |
_delegateRespondsToDidEndDecelerating = [_actualDelegate respondsToSelector:@selector(scrollViewDidEndDecelerating:)]; | |
_delegateRespondsToDidEndScrollingAnimation = [_actualDelegate respondsToSelector:@selector(scrollViewDidEndScrollingAnimation:)]; | |
_delegateRespondsToDidEndZooming = [_actualDelegate respondsToSelector:@selector(scrollViewDidEndZooming:withView:atScale:)]; | |
} | |
#pragma mark - Configuration | |
@synthesize pagingEnabled = _pagingEnabled; | |
- (void)setPagingEnabled:(BOOL)pagingEnabled { | |
if (pagingEnabled == _pagingEnabled) | |
return; | |
_pagingEnabled = pagingEnabled; | |
if (_pagingEnabled) | |
[self snapToPage]; | |
} | |
- (void)setPageWidth:(CGFloat)pageWidth { | |
if (pageWidth == _pageWidth) | |
return; | |
_pageWidth = pageWidth; | |
if (_pagingEnabled) | |
[self snapToPage]; | |
} | |
- (void)setPageHeight:(CGFloat)pageHeight { | |
if (pageHeight == _pageHeight) | |
return; | |
_pageHeight = pageHeight; | |
if (_pagingEnabled) | |
[self snapToPage]; | |
} | |
#pragma mark - Paging support | |
- (void)snapToPage { | |
CGPoint pageOffset; | |
pageOffset.x = [self pageOffsetForComponent:YES]; | |
pageOffset.y = [self pageOffsetForComponent:NO]; | |
CGPoint currentOffset = self.contentOffset; | |
if (!CGPointEqualToPoint(pageOffset, currentOffset)) { | |
_snapping = YES; | |
[self setContentOffset:pageOffset animated:YES]; | |
} | |
_dragVelocity = CGPointZero; | |
_dragDisplacement = CGPointZero; | |
} | |
- (CGFloat)pageOffsetForComponent:(BOOL)isX { | |
if (((isX ? CGRectGetWidth(self.bounds) : CGRectGetHeight(self.bounds)) == 0) || ((isX ? self.contentSize.width : self.contentSize.height) == 0)) | |
return 0; | |
CGFloat pageLength = isX ? _pageWidth : _pageHeight; | |
if (pageLength < FLT_EPSILON) | |
pageLength = isX ? CGRectGetWidth(self.bounds) : CGRectGetHeight(self.bounds); | |
pageLength *= self.zoomScale; | |
CGFloat totalLength = isX ? self.contentSize.width : self.contentSize.height; | |
CGFloat visibleLength = (isX ? CGRectGetWidth(self.bounds) : CGRectGetHeight(self.bounds)) * self.zoomScale; | |
CGFloat currentOffset = isX ? self.contentOffset.x : self.contentOffset.y; | |
CGFloat dragVelocity = isX ? _dragVelocity.x : _dragVelocity.y; | |
CGFloat dragDisplacement = isX ? _dragDisplacement.x : _dragDisplacement.y; | |
CGFloat newOffset; | |
CGFloat index = currentOffset / pageLength; | |
CGFloat lowerIndex = floorf(index); | |
CGFloat upperIndex = ceilf(index); | |
if (ABS(dragDisplacement) < DRAG_DISPLACEMENT_THRESHOLD || dragDisplacement * dragVelocity < 0) { | |
if (index - lowerIndex > upperIndex - index) { | |
index = upperIndex; | |
} else { | |
index = lowerIndex; | |
} | |
} else { | |
if (dragVelocity > 0) { | |
index = upperIndex; | |
} else { | |
index = lowerIndex; | |
} | |
} | |
newOffset = pageLength * index; | |
if (newOffset > totalLength - visibleLength) | |
newOffset = totalLength - visibleLength; | |
if (newOffset < 0) | |
newOffset = 0; | |
return newOffset; | |
} | |
#pragma mark - Scroll view delegate | |
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView { | |
_dragDisplacement = scrollView.contentOffset; | |
if (_delegateRespondsToWillBeginDragging) | |
[_actualDelegate scrollViewWillBeginDragging:scrollView]; | |
} | |
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset { | |
if (_pagingEnabled) { | |
*targetContentOffset = scrollView.contentOffset; | |
_dragVelocity = velocity; | |
_dragDisplacement = CGPointMake(scrollView.contentOffset.x - _dragDisplacement.x, scrollView.contentOffset.y - _dragDisplacement.y); | |
} else { | |
if (_delegateRespondsToWillEndDragging) | |
[_actualDelegate scrollViewWillEndDragging:scrollView withVelocity:velocity targetContentOffset:targetContentOffset]; | |
} | |
} | |
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate { | |
if (!decelerate && _pagingEnabled) | |
[self snapToPage]; | |
if (_delegateRespondsToDidEndDragging) | |
[_actualDelegate scrollViewDidEndDragging:scrollView willDecelerate:decelerate]; | |
} | |
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { | |
if (_pagingEnabled) | |
[self snapToPage]; | |
if (_delegateRespondsToDidEndDecelerating) | |
[_actualDelegate scrollViewDidEndDecelerating:scrollView]; | |
} | |
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView { | |
if (!_snapping && _pagingEnabled) { | |
[self snapToPage]; | |
} else { | |
_snapping = NO; | |
} | |
if (_delegateRespondsToDidEndScrollingAnimation) | |
[_actualDelegate scrollViewDidEndScrollingAnimation:scrollView]; | |
} | |
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale { | |
if (_pagingEnabled) | |
[self snapToPage]; | |
if (_delegateRespondsToDidEndZooming) | |
[_actualDelegate scrollViewDidEndZooming:scrollView withView:view atScale:scale]; | |
} | |
@end |