//
// CardSwitchView.m
// CardSwitchDemo
//
// Created by Apple on 2016/11/9.
// Copyright © 2016年 Apple. All rights reserved.
//
 
#import "CardSwitchView.h"
#import "Card.h"
 
//播放器界面的的寬度所占的比例
static float viewScale = 0.70f;
 
@interface CardSwitchView ()<UIScrollViewDelegate>
{
 //用于切換的ScrollView
 UIScrollView *_scrollView;
 //用于保存各個視圖
 NSMutableArray *_cards;
 //滾動之前的位置
 CGFloat _startPointX;
 //滾動之后的位置
 CGFloat _endPointX;
 //需要居中顯示的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];
 
 //初始化其他參數(shù)
 _cards = [[NSMutableArray alloc] init];
 _currentIndex = 0;
}
 
#pragma mark -
#pragma mark 視圖Frame配置
 
//卡片寬度
-(float)cardWidth
{
 return viewScale*self.bounds.size.width;
}
 
//卡片間隔
-(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 配置輪播圖片
-(void)setCardNumber:(NSInteger)cardNumber
{
 _cardNumber = cardNumber;
 //初始化各個播放器位置
 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
//開始拖動時保存起始位置
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
 _startPointX = scrollView.contentOffset.x;
}
 
//當ScrollView拖動時 變換每個view的大小，并保證居中屏幕的view高度最高
-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
 [self updateCardTransform];
}
 
//滾動結(jié)束，自動回彈到居中卡片
-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
 //滾動到視圖中間位置
 dispatch_async(dispatch_get_main_queue(), ^{
 [self scrollToCurrentCard];
 });
}
 
//卡片自動居中
-(void)scrollToCurrentCard
{
 _endPointX = _scrollView.contentOffset.x;
 //設置滾動最小生效范圍，滾動超過scrollMiniDistance 即視為有切換卡片的意向
 float scrollMiniDistance = self.bounds.size.width/30.0f;
 if (_startPointX - _endPointX > scrollMiniDistance) {
 NSLog(@"向右滑動屏幕");
 if (_currentIndex != 0) {
  _currentIndex -= 1;
 }
 }else if (_endPointX - _startPointX > scrollMiniDistance)
 {
 NSLog(@"向左滑動屏幕");
 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];
}
 
 
//更新每個卡片的大小
-(void)updateCardTransform
{
 for (Card *card in _cards) {
 //獲取卡片所在index
 //獲取ScrollView滾動的位置
 CGFloat scrollOffset = _scrollView.contentOffset.x;
 //獲取卡片中間位置滾動的相對位置
 CGFloat cardCenterX = card.center.x - scrollOffset;
 //獲取卡片中間位置和父視圖中間位置的間距，目標是間距越大卡片越短
 CGFloat apartLength = fabs(self.bounds.size.width/2.0f - cardCenterX);
 //移動的距離和屏幕寬度的的比例
 CGFloat apartScale = apartLength/self.bounds.size.width;
 //把卡片移動范圍固定到 -π/4到 +π/4這一個范圍內(nèi)
 CGFloat scale = fabs(cos(apartScale * M_PI/4));
 //設置卡片的縮放
 card.transform = CGAffineTransformMakeScale(1.0, scale);
 }
}
 
@end