ios动力特效，最重要的一点 属性保持（写了动力特效但是没效果的原因就在这里）

@property (nonatomic, strong) UIDynamicItemBehavior *square1PropertiesBehavior;

@property (nonatomic, strong) UIDynamicItemBehavior *square2PropertiesBehavior;

@property (nonatomic, strong) UIDynamicAnimator *animator;

@property(nonatomic,strong)UIDynamicAnimator*dy;

@end

 

@implementation ViewController

 

- (void)viewDidLoad {

    [super viewDidLoad];

    UIView * apple = [[UIView alloc] initWithFrame:CGRectMake(40,40, 40, 40)];

 

    apple.backgroundColor = [UIColor redColor];

 

    [self.view addSubview:apple];

 

    UIDynamicAnimator *animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];

    UIGravityBehavior *gravityBeahvior = [[UIGravityBehavior alloc] initWithItems:@[apple]];

    UICollisionBehavior *collisionBehavior = [[UICollisionBehavior alloc] initWithItems:@[apple]];

    UIDynamicItemBehavior*behavior = [[UIDynamicItemBehavior alloc] initWithItems:@[apple]];

    //behavior.elasticity = ;

    collisionBehavior.translatesReferenceBoundsIntoBoundary = YES;

    [animator addBehavior:gravityBeahvior];

    [animator addBehavior:collisionBehavior];

    [animator addBehavior:behavior];

 

    self.dy = animator; //属性保持才能有动画效果

 

}

 

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}