#import "ViewController.h"

//屏幕寬度
#define SCREEN_WIDTH [UIScreen mainScreen].bounds.size.width
//圖片高度
#define IMG_HEIGHT 180
//要顯示的圖片總數(shù)
#define MAX_SIZE 7

#import "ViewController.h"

@interface ViewController () <UIScrollViewDelegate>

//滾動視圖
@property (strong, nonatomic) UIScrollView *loopScrollView;
//指示器
@property (strong, nonatomic) UIPageControl *pageIndicator;
//要展示的圖片數(shù)組
@property(strong, nonatomic) NSMutableArray *imgArray;

@end

@implementation ViewController

//懶加載數(shù)組
-(NSMutableArray *)imgArray
{
  if(_imgArray == nil)
  {
    _imgArray = [[NSMutableArray alloc]initWithCapacity:MAX_SIZE];
    //在要展示的5張圖片的前后各加一張圖片，第一張前面加第五張，第五張后面加第一張
    [_imgArray addObject:[UIImage imageNamed:@"img_05.jpg"]];
    for (int i = 1; i< MAX_SIZE - 1; i++) {
      NSString *imgName = [[NSString alloc]initWithFormat:@"img_0%d.jpg", i];
      [_imgArray addObject:[UIImage imageNamed:imgName]];
    }
    [_imgArray addObject:[UIImage imageNamed:@"img_01.jpg"]];

  }
  return _imgArray;
}


- (void)viewDidLoad {
  [super viewDidLoad];

  [self setupScrollView];
  [self setupPageControl];

}

/**
 * 創(chuàng)建UIScrollView并設置其屬性
 */
-(void)setupScrollView
{
  UIScrollView *sc = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 64, SCREEN_WIDTH, IMG_HEIGHT)];

  //創(chuàng)建UIImageView并添加到UIScrollView中
  for (int i = 0; i< MAX_SIZE; i++) {
    UIImageView *img = [[UIImageView alloc]initWithImage:[self.imgArray objectAtIndex:i]];
    img.frame = CGRectMake(SCREEN_WIDTH * i, 0, SCREEN_WIDTH, IMG_HEIGHT);
    [sc addSubview:img];
  }

  //設置UIScrollView的屬性
  sc.contentSize = CGSizeMake(SCREEN_WIDTH * self.imgArray.count, IMG_HEIGHT);
  sc.showsHorizontalScrollIndicator = NO;
  sc.pagingEnabled = YES;
  //剛開始應該滾動到第二張顯示，因為第一張其實是最后一張圖片
  [sc setContentOffset:CGPointMake(SCREEN_WIDTH, 0) animated:NO];


  //設置代理并添加到當前view中
  sc.delegate = self;
  [self.view addSubview:sc];

  self.loopScrollView = sc;
}


/**
 * 創(chuàng)建UIPageControl并設置其屬性
 */
-(void)setupPageControl
{
  //注意frame，這樣設置可以居中顯示
  UIPageControl *pc = [[UIPageControl alloc]initWithFrame:CGRectMake(self.view.center.x - 50, CGRectGetMaxY(self.loopScrollView.frame) - 25 , 100, 25)];
  //設置UIPageControl的屬性并添加到當前view中
  pc.numberOfPages = MAX_SIZE - 2;
  pc.currentPage = 0;
  pc.pageIndicatorTintColor = [UIColor redColor];
  [self.view addSubview:pc];

  self.pageIndicator = pc;

}

//UIScrollView的代理方法，在該方法中改變UIPageControl并且處理邊緣滾動
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
  //獲取當前UIScrollView的位置
  CGPoint offset = [scrollView contentOffset];
  //算出滾動到第幾頁
  int currentPage = offset.x/SCREEN_WIDTH;
  //設置UIPageControl
  self.pageIndicator.currentPage = currentPage - 1;
  //對最后一張和第一張要進行特殊處理
  //1、如果是第一張
  if (currentPage == 0) {
    //下面兩個方法任選其一都可以達到效果，但是注意動畫一定要設置為NO，不然會有視覺會有辣眼睛的感覺
    //方法1
    [self.loopScrollView setContentOffset:CGPointMake(SCREEN_WIDTH * (MAX_SIZE-2), 0) animated:NO];
    //方法2，該方法要求設置contentSize時，任一方向就算不滾動也不能為0，否則無效
    //[self.loopScrollView scrollRectToVisible:CGRectMake(SCREEN_WIDTH * (MAX_SIZE-2), 0, SCREEN_WIDTH, IMG_HEIGHT) animated:NO];
    self.pageIndicator.currentPage = MAX_SIZE - 2;
  }

  //2、如果是最后一張
  else if(currentPage == MAX_SIZE - 1) {
    [self.loopScrollView setContentOffset:CGPointMake(SCREEN_WIDTH, 0) animated:NO];
    //[self.loopScrollView scrollRectToVisible:CGRectMake(SCREEN_WIDTH, 0, SCREEN_WIDTH, IMG_HEIGHT) animated:NO];
    self.pageIndicator.currentPage = 0;
  }
}

@end