objective-c : UIKit Dynamics 기초 (view, barrier, gravity, collision, elasticity, attachmentBehavior)

snippet.m

//UIKit Dynamics 기초 (view, barrier, gravity, collision, elasticity, attachmentBehavior)
//ViewController.m
//.m

#import "ViewController.h"

//UICollisionBehaviorDelegate : receive notifications when items collide
@interface ViewController () <UICollisionBehaviorDelegate> {
    //ivars
    UIDynamicAnimator* _animator;
    UIGravityBehavior* _gravity;
    UICollisionBehavior* _collision;
    BOOL _firstContact;
}

@end

@implementation ViewController

#define debug 1

- (void)viewDidLoad
{
    if (debug==1) {NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));}
    [super viewDidLoad];
    
    //square view
	UIView* square = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)]; //x,y,width,height
    square.backgroundColor = [UIColor grayColor];
    [self.view addSubview:square];
    
    //add an immovable barrier view
    UIView* barrier = [[UIView alloc] initWithFrame:CGRectMake(0, 300, 130, 20)];
    barrier.backgroundColor = [UIColor redColor];
    [self.view addSubview:barrier];
    
    //add gravity
    _animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view]; //UIKit physics engine
    _gravity = [[UIGravityBehavior alloc] initWithItems:@[square]];
    [_animator addBehavior:_gravity];
    
    //add Invisible boundaries and collision behavior
    _collision = [[UICollisionBehavior alloc] initWithItems:@[square]];
    _collision.collisionDelegate = self; //receive notifications when items collide
    
    // add a boundary that coincides with the top edge
    CGPoint rightEdge = CGPointMake(barrier.frame.origin.x +
                                    barrier.frame.size.width,
                                    barrier.frame.origin.y);
    [_collision addBoundaryWithIdentifier:@"barrier" fromPoint:barrier.frame.origin toPoint:rightEdge];
    _collision.translatesReferenceBoundsIntoBoundary = YES; //use the bounds of the reference view
    [_animator addBehavior:_collision];
    
    //block code (dynamic behavior's action property)
    //스퀘어 뷰의 경로 로그로 찍어보기
    _collision.action = ^{
//      NSLog(@"behavior's action property : %@, %@",
//            NSStringFromCGAffineTransform(square.transform),
//            NSStringFromCGPoint(square.center));
    };
    
    //creates an item behavior, associates it with the square
    UIDynamicItemBehavior* itemBehaviour = [[UIDynamicItemBehavior alloc] initWithItems:@[square]];
    itemBehaviour.elasticity = 0.6; 
    [_animator addBehavior:itemBehaviour];
}


#pragma mark - collision behavior delegate methods

- (void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier atPoint:(CGPoint)p
{
    if (debug==1) {NSLog(@"Running %@ '%@'", self.class, NSStringFromSelector(_cmd));}
    NSLog(@"Boundary contact occurred - %@", identifier);
    
    //changes the background color of the colliding item to yellow, and then fades it back to gray again
    UIView *view = (UIView *)item;
    view.backgroundColor = [UIColor yellowColor];
    
    [UIView animateWithDuration:0.3 animations:^{
        view.backgroundColor = [UIColor grayColor];
    }];
    
    //attachment behavior between the barrier and the square
    if (!_firstContact) {
        _firstContact = YES;
        
        UIView* square = [[UIView alloc] initWithFrame:CGRectMake(30, 0, 100, 100)];
        square.backgroundColor = [UIColor grayColor];
        [self.view addSubview:square];
        
        [_collision addItem:square];
        [_gravity addItem:square];
        UIAttachmentBehavior* attach = [[UIAttachmentBehavior alloc]
                                        initWithItem:view
                                        attachedToItem:square];
        [_animator addBehavior:attach];
    }
}

@end