UIKit力学行为包括了:重力(UIGravityBehavior),碰撞(UICollisionBehavior),吸附(UIAttachmentBehavior),推(UIPushBehavior),甩(UISnapBehavior)和行为限制(UIDynamicItemBehavior).

- (void)viewDidAppear:(BOOL)animated {

    [super viewDidAppear:animated];

    _animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];

    //重力行为

    _gravity = [[UIGravityBehavior alloc] initWithItems:@[_box]];

    [_animator addBehavior:_gravity];

    //碰撞行为

    _collision = [[UICollisionBehavior alloc]

                  initWithItems:@[_box]];

    [_collision addBoundaryWithIdentifier:@"barrier" fromPoint:_barrier.frame.origin

                                  toPoint:CGPointMake(_barrier.frame.origin.x + _barrier.frame.size.width, _barrier.frame.origin.y)];

    _collision.translatesReferenceBoundsIntoBoundary = YES;

    _collision.collisionDelegate = self;

    [_animator addBehavior:_collision];

    UIDynamicItemBehavior* itemBehaviour = [[UIDynamicItemBehavior alloc] initWithItems:@[_box]];

    itemBehaviour.elasticity = 0.5;

    [_animator addBehavior:itemBehaviour];

}

- (void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier atPoint:(CGPoint)p {

    if (!_firstContact)

    {

        _firstContact = YES;

        //设置吸附行为

        self.attach = [[UIAttachmentBehavior alloc] initWithItem:_attachmentPoint attachedToItem:_box];

        [self.animator addBehavior:self.attach];

        //设置推行为

        UIPushBehavior* push = [[UIPushBehavior alloc] initWithItems:@[_box] mode:UIPushBehaviorModeInstantaneous];

        //        [push setAngle:-M_PI/4 magnitude:5.0f]; //右上角45度

        CGVector pushDirection = {0.5, -0.5}; //setAngle: magnitude:替代方法

        [push setPushDirection:pushDirection];

        [push setMagnitude:5.0f];

        [_animator addBehavior:push];

    }

}

另一个我个人认为比較实用,就是甩行为

- (void)viewDidAppear:(BOOL)animated {

    [super viewDidAppear:animated];

    _animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];

}

- (IBAction)handleSnapGesture:(UITapGestureRecognizer*)gesture

{

    CGPoint point = [gesture locationInView:self.view];

    // 移除甩行为

    [_animator removeBehavior:_snap];

    _snap = [[UISnapBehavior alloc] initWithItem:_box snapToPoint:point];

    [self.animator addBehavior:_snap];

}

另一个就是类似桌面随手腕角度改变视图位移的方法

//设置山在X轴的偏移范围-50.0~50.0

    UIInterpolatingMotionEffect *mountainEffectX;

    mountainEffectX = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x"

                                                              type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];

    mountainEffectX.maximumRelativeValue = @50.0;

	mountainEffectX.minimumRelativeValue = @-50.0;

    [self.mountain addMotionEffect:mountainEffectX];

    //设置树在X轴的偏移范围-100.0~100.0

    UIInterpolatingMotionEffect *treeEffectX;

    treeEffectX = [[UIInterpolatingMotionEffect alloc] initWithKeyPath:@"center.x"

                                                                      type:UIInterpolatingMotionEffectTypeTiltAlongHorizontalAxis];

    treeEffectX.maximumRelativeValue = @100.0;

	treeEffectX.minimumRelativeValue = @-100.0;

    [self.tree addMotionEffect:treeEffectX];