碰撞检测（CGRectIntersectRect）

Question

我有两个图像：第一个图像大小是50x85，第二个图像大小是50x113。当我触摸屏幕图像上升，显示第二个图像，当我释放屏幕图像下降，第一个图像显示。现在的问题是，当我触摸屏幕碰撞发生的时间早于未触摸屏幕时。

我怎样才能使第二张图像在底部约30px不会发生碰撞，但图像仍然会在那里？

---

编辑：下面是一些代码：

-(void)AstronautMove 
{ 
    [self Collision]; 
    Astronaut.center = CGPointMake(Astronaut.center.x, Astronaut.center.y + Y); 
} 

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    Y = -10; 
    x.image = [UIImage imageNamed:@"y.png"]; 
} 

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    Y = 17; 
    x.image = [UIImage imageNamed:@"x.png"]; 
} 

-(void)Collision 
{ 
    if (CGRectIntersectsRect(Astronaut.frame, Landingarea.frame)) { 
     [self EndGame]; 
     AstronautFire.hidden = YES; 
     RedBorder.hidden = NO; 
     AstronautCrashed.hidden = NO; 
    } 

    if (CGRectIntersectsRect(AstronautFire.frame, Landingarea.frame)) { 
     [self EndGame]; 
     AstronautFire.hidden = YES; 
     RedBorder.hidden = NO; 
     AstronautCrashed.hidden = NO; 
    } 
} 

我只是移动框架上下。底部是着陆区。当宇航员和着陆区域框架碰触时，会发生碰撞。但是，当我将宇航员向上移动时，会显示更大的图像（50x113），而当我将宇航员向下移动时，会显示更小的图像（50x85）。当我靠近着陆区域时，我会按下去显示更大的图像并发生碰撞。

Answer 1

从代码示例中，确实很难遵循你想要做的事情。值得注意的是，目前还不清楚你是如何（或者甚至是如何）制作各种观点的动画。

无论您是否在进行动画制作，从您的代码示例中不清楚AstronautMove被调用的位置。您是否打算从touchesBegan和touchesEnded拨打电话？但根据迄今已分享的内容，我没有看到你打电话AstronautMove，因此看不到你可能如何检测碰撞。

就我个人而言，我原以为你会想动画动画的意见（它会呈现更现实和有吸引力的意见移动）。然后，当动画正在进行时，请继续检查是否有碰撞。在如何“继续检查”方面，您可以使用NSTimer或者更好的方法是使用CADisplayLink（每次屏幕更新时调用方法的机制）。

例如，你可以这样做：

@interface ViewController() 

@property (nonatomic, strong) UIView *view1; 
@property (nonatomic, strong) UIView *view2; 

@property (nonatomic, strong) CADisplayLink *displayLink; 

@end 

@implementation ViewController 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    UIView *view1 = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 50, 50)]; 
    view1.backgroundColor = [UIColor lightGrayColor]; 
    [self.view addSubview:view1]; 
    self.view1 = view1; 

    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(50, 150, 50, 50)]; 
    view2.backgroundColor = [UIColor darkGrayColor]; 
    [self.view addSubview:view2]; 
    self.view2 = view2; 
} 

#pragma mark - Handle touches 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [self startAnimationTo:CGPointMake(50, 250) collisionChecking:YES]; 
} 

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [self startAnimationTo:CGPointMake(50, 50) collisionChecking:NO]; 
} 

#pragma mark - Handle starting and stopping of animation 

- (void)startAnimationTo:(CGPoint)point collisionChecking:(BOOL)collisionChecking 
{ 
    if (collisionChecking) 
     [self startDisplayLink]; 

    [UIView animateWithDuration:2.0 delay:0.0 options:0 animations:^{ 
     CGRect frame = self.view1.frame; 
     frame.origin = point; 
     self.view1.frame = frame; 
    } completion:^(BOOL finished) { 
     // in case we never have collision, let's make sure we stop the display link 
     if (collisionChecking) 
      [self stopDisplayLink]; 
    }]; 
} 

- (void)stopAnimation 
{ 
    CALayer *layer = self.view1.layer.presentationLayer; 

    [self.view1.layer removeAllAnimations]; 
    self.view1.frame = layer.frame; 
    [self stopDisplayLink]; 
} 

#pragma mark - Handle the display link & check for collisions 

- (void)startDisplayLink 
{ 
    self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(checkForCollision:)]; 
    [self.displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; 
} 

- (void)stopDisplayLink 
{ 
    [self.displayLink invalidate]; 
    self.displayLink = nil; 
} 

- (void)checkForCollision:(CADisplayLink *)displayLink 
{ 
    // Note, when checking for collision while an animation is underway, the `frame` of the 
    // view represents the final location of the view, not the current location. To get the 
    // current location, one has to grab the `presentationLayer`. So, we're going to get the 
    // `presentationLayer` of each of the views and use those to determine a collision. 

    CALayer *layer1 = self.view1.layer.presentationLayer; 
    CALayer *layer2 = self.view2.layer.presentationLayer; 

    if (CGRectIntersectsRect(layer1.frame, layer2.frame)) { 
     [self stopAnimation]; 
    } 
} 

@end 

或者，在搭载iOS 7，您可以使用UIKit的动态动画的意见运动，识别程序使用UICollisionBehavior和分配collisionDelegate碰撞：

@interface ViewController() <UICollisionBehaviorDelegate> 

@property (nonatomic, strong) UIView *view1; 
@property (nonatomic, strong) UIView *view2; 

@property (nonatomic, strong) UIDynamicAnimator *animator; 
@property (nonatomic, strong) UISnapBehavior *snap; 

@end 

@implementation ViewController 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    UIView *view1 = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 50, 50)]; 
    view1.backgroundColor = [UIColor lightGrayColor]; 
    [self.view addSubview:view1]; 
    self.view1 = view1; 

    UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(50, 150, 50, 50)]; 
    view2.backgroundColor = [UIColor darkGrayColor]; 
    [self.view addSubview:view2]; 
    self.view2 = view2; 

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

    // create behavior that will detect collisions, calling the `UICollisionBehaviorDelegate` 
    // methods if and when collisions are detected 

    UICollisionBehavior *collision = [[UICollisionBehavior alloc] initWithItems:@[view1, view2]]; 
    collision.translatesReferenceBoundsIntoBoundary = YES; 
    collision.collisionDelegate = self; 
    [self.animator addBehavior:collision]; 

    // in this example, I'm going to fix `view2` where it is, so it doesn't move when 
    // `view1` collides with it 

    UIAttachmentBehavior *attachment = [[UIAttachmentBehavior alloc] initWithItem:self.view2 attachedToAnchor:self.view2.center]; 
    [self.animator addBehavior:attachment]; 

    // finally, let's specify that neither view1 nor view2 should rotate when 
    // snapping, colliding, etc. 

    UIDynamicItemBehavior *noRotate = [[UIDynamicItemBehavior alloc] initWithItems:@[view1, view2]]; 
    noRotate.allowsRotation = NO; 
    [self.animator addBehavior:noRotate]; 
} 

- (void)addSnap:(CGPoint)point 
{ 
    [self removeSnap]; 

    self.snap = [[UISnapBehavior alloc] initWithItem:self.view1 snapToPoint:point]; 
    [self.animator addBehavior:self.snap]; 
    [self.animator updateItemUsingCurrentState:self.view1]; 
} 

- (void)removeSnap 
{ 
    if (self.snap) { 
     [self.animator removeBehavior:self.snap]; 
     self.snap = nil; 
    } 
} 

#pragma mark - Handle touches 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [self addSnap:CGPointMake(75, 225)]; 
} 

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    [self addSnap:CGPointMake(75, 75)]; 
} 

#pragma mark - UICollisionBehaviorDelegate 

// you can use these to be informed when there is a collision 

- (void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier atPoint:(CGPoint)p 
{ 
    NSLog(@"%s", __FUNCTION__); 

    [self removeSnap]; 
} 

- (void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id<UIDynamicItem>)item1 withItem:(id<UIDynamicItem>)item2 atPoint:(CGPoint)p 
{ 
    NSLog(@"%s", __FUNCTION__); 

    [self removeSnap]; 
} 
@end 

或者，对于游戏，SpriteKit可能会更好。你可以谷歌“SpriteKit的例子”，你可能会发现很多很好的介绍SpriteKit。

我知道上述两个例子都不是你正在做的事情，但希望它能说明一些用于识别碰撞的技术，这些技术可以适用于你的应用。