//// ViewController.m// 圖片折疊//// Created by llkj on 2017/8/31.// Copyright © 2017年 LayneCheung. All rights reserved.//#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIImageView *topImageV;@property (weak, nonatomic) IBOutlet UIImageView *buttomImageV;@property (nonatomic, weak) CAGradientLayer *gradientL;@end@implementation ViewController- (void)viewDidLoad {  [super viewDidLoad];  //1.讓上不圖片只顯示上半部分  self.topImageV.layer.contentsRect = CGRectMake(0, 0, 1, 0.5);  //2.讓下不圖片只顯示下半部分  self.buttomImageV.layer.contentsRect = CGRectMake(0, 0.5, 1, 0.5);  self.topImageV.layer.anchorPoint = CGPointMake(0.5, 1);  self.buttomImageV.layer.anchorPoint = CGPointMake(0.5, 0);  //設置漸變層  CAGradientLayer *gradidentL = [CAGradientLayer layer];  gradidentL.frame = self.buttomImageV.bounds;  gradidentL.opacity = 0;  gradidentL.colors = @[(id)[UIColor clearColor].CGColor, (id)[UIColor blackColor].CGColor];  self.gradientL = gradidentL;  [self.buttomImageV.layer addSublayer:gradidentL];}//這里也可以手動給大的ImageView添加一個UIPanGestureRecognizer手勢- (IBAction)pan:(UIPanGestureRecognizer *)pan {  //獲取移動的偏移量  CGPoint transP = [pan translationInView:pan.view];  //讓上部圖片開始旋轉  CGFloat angle = transP.y * M_PI / 200;  //近大遠小效果  CATransform3D transform = CATransform3DIdentity;  //眼睛離屏幕的距離(透視效果)  transform.m34 = -1 / 300.0;  self.gradientL.opacity = transP.y * 1 / 200.0;  self.topImageV.layer.transform = CATransform3DRotate(transform, -angle, 1, 0, 0);  if (pan.state == UIGestureRecognizerStateEnded) {    self.gradientL.opacity = 0;    //上部圖片復位    //usingSpringWithDamping:彈性系數    [UIView animateWithDuration:0.5 delay:0 usingSpringWithDamping:0.5 initialSpringVelocity:0 options:UIViewAnimationOptionCurveLinear animations:^{      self.topImageV.layer.transform = CATransform3DIdentity;    } completion:^(BOOL finished) {    }];  }}@end