How can I check if UIImageView is collided with any other view? - ios

Question

I have one UIImageView and number of UIImageView which are entering in screen after some time interval. I want to check if that one ImageView is collided with any others.
Please help me.

Answer 1

The general process for detecting collisions between rectangular shaped views is to use CGRectIntersectsRect() to see if the frames of two views intersect. So, if you have a NSMutableArray of UIImageView objects, you can perform a fast enumeration through them and look for the collision, something like:
for (UIView* view in self.imageViewsArray)
{
if (CGRectIntersectsRect(view.frame, viewToDetectCollisionWith.frame))
{
// do whatever you want when you detect the collision
}
}
Or, you can use the enumerateObjectsUsingBlock which uses fast enumeration, but gives you both the numeric index, idx, and the individual UIView objects in the array in a single statement:
[self.imageViewsArray enumerateObjectsUsingBlock:^(UIView *view, NSUInteger idx, BOOL *stop) {
if (CGRectIntersectsRect(view.frame, viewToDetectCollisionWith.frame))
{
// do whatever you want when you detect the collision
}
}];
Original answer:
If you're animating the UIImageView objects via the various automated animation techniques, you have to use something like CADisplayLink to check for collisions because iOS is taking care of the animation and you otherwise are not informed of the frame of the various views in the middle of an animation. The CADisplayLink informs your app every time the animation has progressed, so you get information about the location of views as the animation progresses. Sounds like you're not availing yourself of built in animation techniques, but rather using a NSTimer to manually adjust frames, so you might not need the below code. But if you ever pursue a more automated animation, you can use the following technique.
What you can do is use a CADisplayLink to get information about the screen while the animation is in progress:
#import <QuartzCore/QuartzCore.h>
CADisplayLink *displayLink = [CADisplayLink displayLinkWithTarget:self selector:#selector(displayLinkHandler)];
[displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
You might even want to store that in a class property so you can add it and remove it as the view appears and disappears:
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:#selector(displayLinkHandler)];
[self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[self.displayLink removeFromRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
self.displayLink = nil;
}
Then, you can start your animation. I'm just using the standard block-based animation to continually animate the changing of two image view frames, but you'll obviously do whatever is appropriate for your app:
[UIView animateWithDuration:4.0
delay:0.5
options:UIViewAnimationOptionAutoreverse | UIViewAnimationOptionRepeat
animations:^{
self.imageView1.frame = ... // I set the frame here
self.imageView2.frame = ... // I set the frame here
}
completion:nil];
Now I can detect when these two frames collide (i.e., whether their frames intersect) with this CADisplayLink handler which grabs the relevant presentationLayer properties to get the "in progress" frame coordinates:
- (void)displayLinkHandler
{
id presentationLayer1 = self.imageView1.layer.presentationLayer;
id presentationLayer2 = self.imageView2.layer.presentationLayer;
BOOL nowIntersecting = CGRectIntersectsRect([presentationLayer1 frame], [presentationLayer2 frame]);
// I'll keep track of whether the two views were intersected in a class property,
// and therefore only display a message if the intersected state changes.
if (nowIntersecting != self.wasIntersected)
{
if (nowIntersecting)
NSLog(#"imageviews now intersecting");
else
NSLog(#"imageviews no longer intersecting");
self.wasIntersected = nowIntersecting;
}
}
By the way, you may need to add Quartz 2D, the QuartzCore.framework, to your project. See the Project Editor Help.