CWFlowLayout.m
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//
// CWFlowLayout.m
// CWCarousel
//
// Created by WangChen on 2018/4/3.
// Copyright © 2018年 ChenWang. All rights reserved.
//
#import "CWFlowLayout.h"
@interface CWFlowLayout () {
}
/**
默认轮播图宽度
*/
@property (nonatomic, assign) CGFloat defaultItemWidth;
@property (nonatomic, assign) CGFloat factItemSpace;
@end
@implementation CWFlowLayout
- (instancetype)initWithStyle:(CWCarouselStyle)style {
if(self = [super init]) {
self.style = style;
[self initial];
}
return self;
}
- (void)dealloc {
NSLog(@"%s", __func__);
}
- (void)initial {
self.itemSpace_H = 0;
self.itemSpace_V = 0;
self.minScale = 0.8;
self.maxScale = 1.2;
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
if (self.style == CWCarouselStyle_Unknow) {
return NO;
}
if (self.style == CWCarouselStyle_Normal) {
return NO;
}
if (self.style == CWCarouselStyle_H_1) {
return NO;
}
return YES;
}
- (void)prepareLayout {
[super prepareLayout];
switch (self.style) {
case CWCarouselStyle_Normal: {
CGFloat width = CGRectGetWidth(self.collectionView.frame);
CGFloat height = CGRectGetHeight(self.collectionView.frame);
self.itemWidth = width;
self.itemSize = CGSizeMake(width, height);
self.minimumLineSpacing = self.itemSpace_H;
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
}
break;
case CWCarouselStyle_H_1: {
CGFloat width = self.itemWidth <= 0 ? self.defaultItemWidth : self.itemWidth;
self.itemWidth = width;
CGFloat height = CGRectGetHeight(self.collectionView.frame);
self.itemSize = CGSizeMake(width, height);
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
self.minimumLineSpacing = self.itemSpace_H;
break;
}
case CWCarouselStyle_H_2: {
CGFloat width = self.itemWidth <= 0 ? self.defaultItemWidth : self.itemWidth;
self.itemWidth = width;
CGFloat height = CGRectGetHeight(self.collectionView.frame);
self.itemSize = CGSizeMake(width, height);
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
CGFloat padding = width * (1 - self.minScale) * 0.5;
self.factItemSpace = 0;
self.minimumLineSpacing = self.itemSpace_H - padding;
}
break;
case CWCarouselStyle_H_3: {
CGFloat width = self.itemWidth <= 0 ? self.defaultItemWidth : self.itemWidth;
self.itemWidth = width;
CGFloat height = CGRectGetHeight(self.collectionView.frame);
self.itemSize = CGSizeMake(width, height);
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
CGFloat padding = width * (1 - self.minScale) * 0.5;
self.factItemSpace = 0;
// if(width * (1 - self.minScale) * 0.5 < self.itemSpace_H) {
// self.factItemSpace = self.itemSpace_H - width * (1 - self.minScale) * 0.5;
// }
// self.minimumLineSpacing = self.factItemSpace;
self.minimumLineSpacing = self.itemSpace_H - padding;
}
break;
default:
break;
}
}
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect {
if (self.style == CWCarouselStyle_Unknow ||
self.style == CWCarouselStyle_Normal ||
self.style == CWCarouselStyle_H_1) {
return [super layoutAttributesForElementsInRect:rect];
}
NSArray<UICollectionViewLayoutAttributes *> *arr = [[NSArray alloc] initWithArray:[super layoutAttributesForElementsInRect:rect] copyItems:YES];
CGFloat centerX = self.collectionView.contentOffset.x + CGRectGetWidth(self.collectionView.frame) * 0.5;
__block CGFloat maxScale = 0;
__block UICollectionViewLayoutAttributes *attri = nil;
[arr enumerateObjectsUsingBlock:^(UICollectionViewLayoutAttributes * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
CGFloat space = ABS(obj.center.x - centerX);
space = MIN(space, self.itemWidth + self.factItemSpace);
obj.zIndex = 0;
if(space >= 0) {
CGFloat scale = 1;
if (self.style == CWCarouselStyle_H_2 ||
self.style == CWCarouselStyle_H_3) {
/**
公式: scale = k * space + a
其中: k = (minScale - 1) / (itemWidth + factItemSpace)
其中: a = 1
综上所述:
scale = (minScale - 1) / (itemWitdh + factItemSpace) * space + 1
*/
scale = (self.minScale - 1) / (self.itemWidth + self.factItemSpace) * space + 1;
}else {
// scale = -((self.maxScale - 1) / width) * space + self.maxScale;
}
obj.transform = CGAffineTransformMakeScale(scale, scale);
if(maxScale < scale) {
maxScale = scale;
attri = obj;
}
}
}];
if (attri) {
attri.zIndex = 1;
}
return arr;
}
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity {
return proposedContentOffset;
}
#pragma mark - Property
- (CGFloat)defaultItemWidth {
switch (self.style) {
case CWCarouselStyle_Unknow:
case CWCarouselStyle_Normal:
return self.collectionView.frame.size.width;
break;
case CWCarouselStyle_H_1:
case CWCarouselStyle_H_2:
case CWCarouselStyle_H_3:
return self.collectionView.frame.size.width * 0.75;
break;
default:
break;
}
}
- (void)setMaxScale:(CGFloat)maxScale {
_maxScale = maxScale;
if(maxScale < 1) {
_maxScale = 1;
}
}
- (void)setMinScale:(CGFloat)minScale {
_minScale = minScale;
if(minScale < 0) {
_minScale = 0.1;
}
if (minScale >= 1) {
_minScale = 1;
}
}
@end