UIDynamic Animation是iOS 7引入的一个动态库，用来模拟现实世界的物理模型，用掉落的蘑菇暂看看其基本的特性。
mushroom.gif
#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) UIDynamicAnimator *animator;
@property (nonatomic, strong) UIGravityBehavior *gravityBeahvior;
@property (nonatomic, strong) UICollisionBehavior *collisionBehavior;
@property (nonatomic, strong) UIDynamicItemBehavior *itemBehavior;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
UIGestureRecognizer *gesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];
[self.view addGestureRecognizer:gesture];
[self setUpDownMushroom];
}
- (void)dealloc {
[self.animator removeAllBehaviors];
}
- (void)setUpDownMushroom {
// 相当于一个容器，为下面动画提供上下文
self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
// 重力
self.gravityBeahvior = [[UIGravityBehavior alloc] init];
// 碰撞
self.collisionBehavior = [[UICollisionBehavior alloc] init];
// 碰撞边界为可碰撞边界
self.collisionBehavior.translatesReferenceBoundsIntoBoundary = YES;
// 物体属性
self.itemBehavior = [[UIDynamicItemBehavior alloc] init];
self.itemBehavior.elasticity = 0.7; // 改变弹性
self.itemBehavior.friction = 0.5; // 摩擦
self.itemBehavior.resistance = 0.5; // 阻力
[self.animator addBehavior:self.gravityBeahvior];
[self.animator addBehavior:self.collisionBehavior];
[self.animator addBehavior:self.itemBehavior];
}
- (void)tapped:(UITapGestureRecognizer *)gesture {
UIImage *image = [UIImage imageNamed:@"mushroom"];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
[self.view addSubview:imageView];
CGPoint tappedPosition = [gesture locationInView:gesture.view];
imageView.center = tappedPosition;
[self.gravityBeahvior addItem:imageView];
[self.collisionBehavior addItem:imageView];
[self.itemBehavior addItem:imageView];
}
@end
简单了解下，上述用到的三大类：
- UIDynamicAnimator，封装了底层 iOS 物理引擎，为动力项提供物理相关的功能和动画。（animator）
- UIDynamicBehavior，动力行为，为动力项提供不同的物理行为（gravityBeahvior、collisionBehavior、itemBehavior）
- UIDynamicItem，动力项，相当于现实世界中的一个基本物体（imageView）
三个类对应的关系
此处作为抛砖引玉，什么是 UIKit Dynamics 这篇博文非常详细，要用到这块的时候，可一步一步的去了解。
PS：场景来自：【iOS开发范例实战宝典.进阶篇】。
