AutoLayout And Animation

 1 #import "ViewController.h"
 2 
 3 @interface ViewController ()
 4 @property (weak, nonatomic) IBOutlet UIView *animationView;
 5 
 6 @property (nonatomic, assign) BOOL isForwadAnimation;
 7 @end
 8 
 9 @implementation ViewController
10 
11 - (void)viewDidLoad {
12     [super viewDidLoad];
13     // Do any additional setup after loading the view, typically from a nib.
14     self.isForwadAnimation = NO;
15 }
16 
17 // 点击view时改变animationView约束中与Top的间距
18 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
19 {
20     if(self.isForwadAnimation)
21     {
22         [self replaceTopConstrainOnView:self.animationView contant:20];
23     }
24     else
25     {
26         [self replaceTopConstrainOnView:self.animationView contant:200];
27     }
28     // 启动动画
29     [self animateConstraints];
30     self.isForwadAnimation = !self.isForwadAnimation;
31 }
32 
33 // 改变约束的值
34 - (void)replaceTopConstrainOnView:(UIView *)view contant:(float)contant
35 {
36     [self.view.constraints enumerateObjectsUsingBlock:^(NSLayoutConstraint *constraint, NSUInteger idx, BOOL *stop) {
37         if(constraint.firstItem == view && constraint.firstAttribute == NSLayoutAttributeTop)
38         {
39             constraint.constant = contant;
40         }
41     }];
42 }
43 
44 // 利用UIView的类方法做动画
45 - (void)animateConstraints
46 {
47     [UIView animateWithDuration:2.0 animations:^{
48         [self.view layoutIfNeeded];
49     }];
50 }