iOS开发——新特性OC篇&iOS9多任务处理

iOS9多任务处理

升级到iOS9的小伙伴都会发现ios9有一个非常炫酷的界面，之前使用的CollectionView实现，但是现在却给用户不一样的体验，笔者就简单研究了一下，并且找了一个小例子。

首先pod一下：

• platform :ios, "8.0"
• pod "iCarousel"

关于iCarousel（牛逼第三方）这里就不多说，等笔者有机会深入研究源码在分享，

然后撒野别不管，把下面的代码拷贝到你的控制器实现文件中，运行

  1 /**
  2  *  iCarousel原理
  3  *
  4  *  @param <iCarouselDelegate <iCarouselDelegate description
  5  *  @param nonatomic          nonatomic description
  6  *  @param strong             strong description
  7  *
  8  *  @return
  9  */
 10
 11 /*
 12 iCarousel并不是一个UIScrollView 也并没有包含任何UIScrollView作为subView
 13 iCarousel通过UIPanGestureRecognizer来计算和维护scrollOffset这个变量
 14 iCarousel通过scrollOffset来驱动整个动画过程
 15 iCarousel本身并不会改变itemView的位置 而是靠修改itemView的layer.transform来实现位移和形变
 16 */
 17
 18 #import "iCocosController.h"
 19
 20 #import <iCarousel.h>
 21
 22 @interface iCocosController ()<iCarouselDelegate,iCarouselDataSource>
 23
 24 @property (nonatomic, strong) iCarousel *carousel;
 25 @property (nonatomic, assign) CGSize cardSize;
 26
 27 @end
 28
 29 @implementation iCocosController
 30
 31 - (void)viewDidLoad {
 32     [super viewDidLoad];
 33
 34     CGFloat cardWidth = [UIScreen mainScreen].bounds.size.width*5.0f/7.0f;
 35     self.cardSize = CGSizeMake(cardWidth, cardWidth*16.0f/9.0f);
 36     self.view.backgroundColor = [UIColor blackColor];
 37
 38     self.carousel = [[iCarousel alloc] initWithFrame:[UIScreen mainScreen].bounds];
 39     [self.view addSubview:self.carousel];
 40     self.carousel.delegate = self;
 41     self.carousel.dataSource = self;
 42     self.carousel.type = iCarouselTypeCustom;
 43     self.carousel.bounceDistance = 0.2f;
 44 }
 45
 46
 47 - (NSInteger)numberOfItemsInCarousel:(iCarousel *)carousel
 48 {
 49     return 15;
 50 }
 51 - (CGFloat)carouselItemWidth:(iCarousel *)carousel
 52 {
 53     return self.cardSize.width;
 54 }
 55 - (UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSInteger)index reusingView:(UIView *)view
 56 {
 57     UIView *cardView = view;
 58
 59     if ( !cardView )
 60     {
 61         cardView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.cardSize.width, self.cardSize.height)];
 62
 63         UIImageView *imageView = [[UIImageView alloc] initWithFrame:cardView.bounds];
 64         [cardView addSubview:imageView];
 65         imageView.contentMode = UIViewContentModeScaleAspectFill;
 66         imageView.backgroundColor = [UIColor whiteColor];
 67
 68         cardView.layer.shadowPath = [UIBezierPath bezierPathWithRoundedRect:imageView.frame cornerRadius:5.0f].CGPath;
 69         cardView.layer.shadowRadius = 3.0f;
 70         cardView.layer.shadowColor = [UIColor blackColor].CGColor;
 71         cardView.layer.shadowOpacity = 0.5f;
 72         cardView.layer.shadowOffset = CGSizeMake(0, 0);
 73
 74         CAShapeLayer *layer = [CAShapeLayer layer];
 75         layer.frame = imageView.bounds;
 76         layer.path = [UIBezierPath bezierPathWithRoundedRect:imageView.bounds cornerRadius:5.0f].CGPath;
 77         imageView.layer.mask = layer;
 78     }
 79
 80     return cardView;
 81 }
 82
 83 /**
 84  *  灵魂
 85  */
 86 //- (CATransform3D)carousel:(iCarousel *)carousel itemTransformForOffset:(CGFloat)offset
 87
 88 //- (UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSInteger)index reusingView:(UIView *)view
 89 //{
 90 //    UIView *cardView = view;
 91 //
 92 //    if ( !cardView )
 93 //    {
 94 //        cardView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.cardSize.width, self.cardSize.height)];
 95 //
 96 //        ...
 97 //        ...
 98 //
 99 //        //添加一个lbl
100 //        UILabel *lbl = [[UILabel alloc] initWithFrame:cardView.bounds];
101 //        lbl.text = [@(index) stringValue];
102 //        [cardView addSubview:lbl];
103 //        lbl.font = [UIFont boldSystemFontOfSize:200];
104 //        lbl.textAlignment = NSTextAlignmentCenter;
105 //    }
106 //
107 //    return cardView;
108 //}
109
110 - (CATransform3D)carousel:(iCarousel *)carousel itemTransformForOffset:(CGFloat)offset baseTransform:(CATransform3D)transform
111 {
112     NSLog(@"%f",offset);
113
114 //    return transform;
115 //    return CATransform3DTranslate(transform, offset * self.cardSize.width, 0, 0);
116     CGFloat scale = [self scaleByOffset:offset];
117     CGFloat translation = [self translationByOffset:offset];
118
119 //    return CATransform3DScale(CATransform3DTranslate(transform, translation * self.cardSize.width, 0, 0), scale, scale, 1.0f);
120     return CATransform3DScale(CATransform3DTranslate(transform, translation * self.cardSize.width, 0, offset), scale, scale, 1.0f);
121 }
122 - (void)carouselDidScroll:(iCarousel *)carousel
123 {
124     for ( UIView *view in carousel.visibleItemViews)
125     {
126         CGFloat offset = [carousel offsetForItemAtIndex:[carousel indexOfItemView:view]];
127
128         if ( offset < -3.0 )
129         {
130             view.alpha = 0.0f;
131         }
132         else if ( offset < -2.0f)
133         {
134             view.alpha = offset + 3.0f;
135         }
136         else
137         {
138             view.alpha = 1.0f;
139         }
140     }
141 }
142 //形变是线性的就ok了
143 - (CGFloat)scaleByOffset:(CGFloat)offset
144 {
145     return offset*0.04f + 1.0f;
146 }
147 //位移通过得到的公式来计算
148 - (CGFloat)translationByOffset:(CGFloat)offset
149 {
150     CGFloat z = 5.0f/4.0f;
151     CGFloat n = 5.0f/8.0f;
152
153     //z/n是临界值 >=这个值时 我们就把itemView放到比较远的地方不让他显示在屏幕上就可以了
154     if ( offset >= z/n )
155     {
156         return 2.0f;
157     }
158
159     return 1/(z-n*offset)-1/z;
160 }
161
162 @end

最后你会发现奇怪的现象，就是非常简单的实现了多任务