动力特效总结：
UIGravityBehavior 重力特效UICollisionBehavior 边界碰撞特效UIAttachmentBehavior 吸附特效UISnapBehavior 瞬移特效UIPushBehavior 推力特效1，先来一个完整的demo
@interface ViewController () { UIDynamicAnimator *_animator; UIView *_headerView; UIAttachmentBehavior *_leaderAttach; } @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // 1. 定义小圆球的frame CGFloat width = 20; CGFloat height = width; CGFloat startX = 100; CGFloat y = 0; // 创建一个可变数组用来存放小圆球 NSMutableArray *roundArrM = [NSMutableArray array]; // 2. 循环创建小圆球 for (NSInteger i = 0; i < 9; i ++) { // 2.1 实例化并设置frame CGFloat x = startX + i * width; UIView *roundV = [[UIView alloc] init]; // 2.2 设置小球颜色 roundV.backgroundColor = [UIColor colorWithRed:arc4random_uniform(256) / 255.0 green:arc4random_uniform(256) / 255.0 blue:arc4random_uniform(256) / 255.0 alpha:1.0]; // 2.3 设置圆角 roundV.layer.cornerRadius = 10; // 最后一个需要设置为大球 if (i == 8) { width = 40; height = width; roundV.layer.cornerRadius = 20; _headerView = roundV; } roundV.frame = CGRectMake(x, y, width, height); // 2.4 添加到当前view [self.view addSubview:roundV]; // 2.5 添加到数组中 [roundArrM addObject:roundV]; } // 3. 创建仿真者 UIDynamicAnimator *animater = [[UIDynamicAnimator alloc] initWithReferenceView:self.view]; _animator = animater; // 4. 添加重力行为 UIGravityBehavior *gravity = [[UIGravityBehavior alloc] initWithItems:roundArrM]; [animater addBehavior:gravity]; // 5. 添加边缘碰撞检测 UICollisionBehavior *collision = [[UICollisionBehavior alloc] initWithItems:roundArrM]; collision.translatesReferenceBoundsIntoBoundary = YES; [animater addBehavior:collision]; // 6. 添加多元素的附着行为 for (NSInteger i = 0; i < roundArrM.count - 1; i++) { // 给每个元素都添加一个一个附着行为，并添加到仿真者 UIAttachmentBehavior *attachment = [[UIAttachmentBehavior alloc] initWithItem:roundArrM[i] attachedToItem:roundArrM[i + 1]]; [animater addBehavior:attachment]; } // 7. 添加手势识别器 UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panAction:)]; [self.view addGestureRecognizer:pan]; } - (void)panAction:(UIPanGestureRecognizer *)pan { // 获取触摸点 CGPoint loc = [pan locationInView:self.view]; if (pan.state == UIGestureRecognizerStateBegan) { // 与headerView建立附着关系 _leaderAttach = [[UIAttachmentBehavior alloc] initWithItem:_headerView attachedToAnchor:loc]; [_animator addBehavior:_leaderAttach]; } else if (pan.state == UIGestureRecognizerStateChanged) { // 如果拖拽正在进行，就转换附着点 _leaderAttach.anchorPoint = loc; } else if (pan.state == UIGestureRecognizerStateEnded) { // 如果拖拽结束，就移除附着行为 [_animator removeBehavior:_leaderAttach]; } }2，瞬移的demo
@interface Test5ViewController () { UIDynamicAnimator *_animator; UIView *_roundV; UISnapBehavior *_snapBehavior; } @end @implementation Test5ViewController - (void)viewDidLoad { [super viewDidLoad]; self.view.backgroundColor = [UIColor whiteColor]; UIView *roundV = [[UIView alloc]initWithFrame:CGRectMake(WIDTH/2, 0, 40, 40)]; [self.view addSubview:roundV]; _roundV = roundV; UIView *subView = [[UIView alloc]initWithFrame:CGRectMake(WIDTH/2-40, 0, 30, 30)]; [self.view addSubview:subView]; subView.backgroundColor = [UIColor greenColor]; subView.layer.cornerRadius = 15.0f; roundV.backgroundColor = [UIColor redColor]; roundV.layer.cornerRadius = 20; UIDynamicAnimator *animator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view]; //一定要生成实例变量或者属性，否则不会访问setter方法，使视图无法实现动力效果 _animator = animator; //添加手势 UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(panAction:)]; [self.view addGestureRecognizer:pan]; // Do any additional setup after loading the view. } -(void)panAction:(UIPanGestureRecognizer*)pan{ //获取手势的位置坐标 CGPoint local = [pan locationInView: self.view]; if (pan.state == UIGestureRecognizerStateBegan) { _snapBehavior = [[UISnapBehavior alloc]initWithItem:_roundV snapToPoint:local]; //阻尼系数 _snapBehavior.damping = 0.7; [_animator addBehavior:_snapBehavior]; }else if(pan.state == UIGestureRecognizerStateChanged){ _snapBehavior.snapPoint = local; }else if(pan.state == UIGestureRecognizerStateEnded) { [_animator removeBehavior:_snapBehavior]; } }