iOS利用余弦函数实现卡片浏览工具

//// CardSwitchView.m// CardSwitchDemo//// Created by Apple on 2016/11/9.// Copyright © 2016年 Apple. All rights reserved.// #import "CardSwitchView.h"#import "Card.h" //播放器界面的的宽度所占的比例static float viewScale = 0.70f; @interface CardSwitchView ()<UIScrollViewDelegate>{ //用于切换的ScrollView UIScrollView *_scrollView; //用于保存各个视图 NSMutableArray *_cards; //滚动之前的位置 CGFloat _startPointX; //滚动之后的位置 CGFloat _endPointX; //需要居中显示的index NSInteger _currentIndex;}@end @implementation CardSwitchView -(instancetype)initWithFrame:(CGRect)frame{ if (self = [super initWithFrame:frame]) { [self buildLayout]; } return self;}  -(void)buildLayout{ //初始化ScrollView _scrollView = [[UIScrollView alloc] initWithFrame:self.bounds]; _scrollView.delegate = self; _scrollView.showsHorizontalScrollIndicator = false; [self addSubview:_scrollView];  //初始化其他参数 _cards = [[NSMutableArray alloc] init]; _currentIndex = 0;} #pragma mark -#pragma mark 视图Frame配置 //卡片宽度-(float)cardWidth{ return viewScale*self.bounds.size.width;} //卡片间隔-(float)margin{ return (self.bounds.size.width - [self cardWidth])/4;}//卡片起始位置-(float)startX{ return (self.bounds.size.width - [self cardWidth])/2.0f;} #pragma mark -#pragma mark 配置轮播图片-(void)setCardNumber:(NSInteger)cardNumber{ _cardNumber = cardNumber; //初始化各个播放器位置 for (NSInteger i = 0; i<cardNumber; i++ ) { //第一步 在ScrollView上添加卡片 float viewX = [self startX] + i*([self cardWidth] + [self margin]); Card* card = [[Card alloc] initWithFrame:CGRectMake(viewX, 0, [self cardWidth], self.bounds.size.height)]; card.layer.borderWidth = 1.0f; card.index = i; [_scrollView addSubview:card]; [_cards addObject:card]; [_scrollView setContentSize:CGSizeMake(card.frame.origin.x + [self cardWidth] + 2*[self margin], 0)]; } //更新卡片的大小 [self updateCardTransform];} #pragma mark -#pragma mark ScrollView代理方法//开始拖动时保存起始位置-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{ _startPointX = scrollView.contentOffset.x;} //当ScrollView拖动时 变换每个view的大小，并保证居中屏幕的view高度最高-(void)scrollViewDidScroll:(UIScrollView *)scrollView{ [self updateCardTransform];} //滚动结束，自动回弹到居中卡片-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{ //滚动到视图中间位置 dispatch_async(dispatch_get_main_queue(), ^{ [self scrollToCurrentCard]; });} //卡片自动居中-(void)scrollToCurrentCard{ _endPointX = _scrollView.contentOffset.x; //设置滚动最小生效范围，滚动超过scrollMiniDistance 即视为有切换卡片的意向 float scrollMiniDistance = self.bounds.size.width/30.0f; if (_startPointX - _endPointX > scrollMiniDistance) { NSLog(@"向右滑动屏幕"); if (_currentIndex != 0) {  _currentIndex -= 1; } }else if (_endPointX - _startPointX > scrollMiniDistance) { NSLog(@"向左滑动屏幕"); if (_currentIndex != _cards.count - 1) {  _currentIndex += 1; } } float viewX = [self startX] + _currentIndex*([self cardWidth] + [self margin]); float needX = viewX - [self startX]; [_scrollView setContentOffset:CGPointMake(needX, 0) animated:true];}  //更新每个卡片的大小-(void)updateCardTransform{ for (Card *card in _cards) { //获取卡片所在index //获取ScrollView滚动的位置 CGFloat scrollOffset = _scrollView.contentOffset.x; //获取卡片中间位置滚动的相对位置 CGFloat cardCenterX = card.center.x - scrollOffset; //获取卡片中间位置和父视图中间位置的间距，目标是间距越大卡片越短 CGFloat apartLength = fabs(self.bounds.size.width/2.0f - cardCenterX); //移动的距离和屏幕宽度的的比例 CGFloat apartScale = apartLength/self.bounds.size.width; //把卡片移动范围固定到 -π/4到 +π/4这一个范围内 CGFloat scale = fabs(cos(apartScale * M_PI/4)); //设置卡片的缩放 card.transform = CGAffineTransformMakeScale(1.0, scale); }} @end