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problem with collision of two images
HI everyone I'm french so scuse me for my english: SO I have two images(flakeView and viewToRotate) one that is moving, the other static in the center of the screen.What I want is : if flakeView and viewToRotate collide : do something. But the problem is that they intersects before they actually touch and I don't know where is the problem.
here is the code:
UIImageView *flakeView = [[UIImageView alloc] initWithImage:flakeImage];
// use the random() function to randomize up our flake attributes
int startX = round(random() % 480);
// set the flake start position
flakeView.center = CGPointMake(startX, -20.0);
flakeView.alpha = 1;
CGRect frame = CGRectMake(startX, -20.0, 30, 30);
flakeView.frame = frame;
// put the flake in our main view
[self.view addSubview:flakeView];
[UIView beginAnimations:nil context:flakeView];
// set up how fast the flake will fall
[UIView setAnimationDuration:7 ];
// set the postion where flake will move to
flakeView.center = viewToRotate.center;
// set a stop callback so we can cleanup the flake when it reaches the
// end of its animation
[UIView setAnimationDelegate:self];
[UIView commitAnimations];
if (CGRectIntersectsRect(flakeView.frame, viewToRotate.frame) == 1){
//do something
}
}
How can I solve this please ?
Are you saying that CGRectIntersectsRect is true before the images touch?
If the graphic within the UIImageView is smaller than the frame the UIImageViews will, in fact, touch and even intersect before the visible images touch. I wonder if that's your problem.
If so, the solution would be to use as much of the frame as possible.
The other condition is that you have a non-rectangular shape inside your UIImageView. If you have the image of circle then CGRectIntersectsRect can return true when the circles are not touching (but their frames do).
The solution to the above is to either supplement CGRectIntersectsRect with code to check the bounds of the image being portrayed or to create your own collision detection code (my preference) to deal with the unique cases surrounding your shape.
Related
Well here is my problem:
I have two images : flakeImage and ViewToRotate. What I want is that if flakeImage touches ViewToRotate, ViewToRotate.alpha=0.5; but when FlakeImage appears on the screen ViewToRotate.alpha=0.5; without touching it. I think it's a problem with my view beacause I have :
UIImageView* flakeView = [[UIImageView alloc] initWithImage:flakeImage];
here is the code :
UIImageView* flakeView = [[UIImageView alloc] initWithImage:flakeImage];
// use the random() function to randomize up our flake attributes
int startY = round(random() % 320);
// set the flake start position
flakeView.center = CGPointMake(490, startY);
flakeView.alpha = 1;
// put the flake in our main view
[self.view addSubview:flakeView];
[UIView beginAnimations:nil context:flakeView];
// set up how fast the flake will fall
[UIView setAnimationDuration:7 ];
// set the postion where flake will move to
flakeView.center = viewToRotate.center;
// set a stop callback so we can cleanup the flake when it reaches the
// end of its animation
[UIView setAnimationDelegate:self];
[UIView commitAnimations];
How can I solve this please ?
if someone could help me it would be very cool.
I have a bit of sophomoric experience with this, having written http://itunes.apple.com/us/app/balls/id372269039?mt=8. If you check that app out, you will see a bit of the same problem. This topic is a pretty deep rabbit hole. WHen I started that app, I didn't even know how to write a decent game loop. You will need that first because you need to do precise time-step calculations. AFA the collisions, you update your model and view separately, so if you update the model and objects overlap, you need to back them up until they don't collide and then update your view with the result. If you plan to have a lot of colliding objects, you may hit a wall using UIViews. To complicate things more, if your objects are round, CGRectIntersectsRect won't exactly work. That complicates the math a bit, but it's not too bad. With my app, I found it quite difficult to get the physics to look realistic. THe problem became that ball A and B overlap, so you back them up, then they now intersect other balls, etc, etc. This link is a good starting point, but there are quite a few examples of code out there that "almost" work.
CGRect has a intersection function. The frames of UIViews are CGRects.
if (CGRectIntersectsRect(view1.frame, view2.frame) == 1)
NSLog(#"The views intersect");
else
NSLog(#"The views do not intersect");
The problem I foresee is that if the rects have lots of whitespace, they will appear to intersect before they actually touch
Secondly, you should switch up to block animations. It's strongly encouraged
UIImageView* flakeView = [[[UIImageView alloc] initWithImage:flakeImage] autorelease];
// use the random() function to randomize up our flake attributes
int startY = round(random() % 320);
// set the flake start position
flakeView.center = CGPointMake(490, startY);
flakeView.alpha = 1;
// put the flake in our main view
[self.view addSubview:flakeView];
[UIView animateWithDuration:.7
animations:^ {
// set the postion where flake will move to
flakeView.center = viewToRotate.center;
};
Did this all from memory, no idea if there are errors.
Circular Collision:
a^2 + b^2 < c^2 means they collide
if(pow(view2.frame.origin.x - view1.frame.origin.x, 2) +
pow(view2.frame.origin.y - view1.frame.origin.y, 2) <
pow(view1.frame.size.width/2, 2))
{
//collision
}
else
{
//no collision
}
Again, all from memory, check for errors on your own
I have 4 views and i am drawing circles inside these views.The user is able to move these views.How can i get the position of each view?
If your views are instance variables in your class you can use view.frame or view.center but your question is quite low on details so I'm just shooting in the dark.
CGPoint origin = view.origin;
CGPoint center = view.center;
CGRect frame = view.frame;
All these things can be used to get what you want.
CoreAnimation is a pretty easy thing, but:
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:30];
MyImageView.frame = CGRectOffset(MyImageView.frame, 100, 0);
[UIView commitAnimations];
I want to move the ImageView by 100 Pixel veeeery slowly. Therefore all positioning values are double I expect the Layoutsystem to position the items with subpixel accuracy.
Butt when I watch this animation i see the ImageView "jumping" pixelwise instead of a smooth traveling.
Any ideas to come to a real subpixelpositioning?
I also tried to set the position with a timer and recalculate the frame-values, but same effect.
Update:
In an other part of my App I use the Accelerometer to update the position of a ImageView, and do basicly calculate the position ad size of the graphic an then do:
MyImageView.frame = newCGRect;
I get around 60 Updates/s from the Accelerometer and added the LowPass-Filter from the Accelerometer example from Apple.
Here the positioning is perfect?!?!
Why does this do not happen with CoreAnimation?
Thanks for any help.
Try using CGAffineTransformTranslate(MyImageView.transform, 100, 0) instead of CGRectOffset.
Reference here:
http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/CGAffineTransform/Reference/reference.html
If you use CABasicAnimation in QuartzCore framework, you can smoothen your animation using "CAMediaTimingFunction". Built-in alternatives worked for me but as far as I know you can define your own timing functions as well.
CABasicAnimation *starShineAnimation = [CABasicAnimation animationWithKeyPath:#"transform.rotation"];
starShineAnimation.removedOnCompletion = NO;
starShineAnimation.fillMode = kCAFillModeForwards;
starShineAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
....
My goal is simple; I want to create a program that displays an UIImage, and when swiped from bottom to top, displays another UIImage. The images here could be a happy face/sad face. The sad face should be the starting point, the happy face the end point. When swiping your finger the part below the finger should be showing the happy face.
So far I tried solving this with the frame and bounds properties of the UIImageview I used for the happy face image.
What this piece of code does is wrong, because the transition starts in the center of the screen and not the bottom. Notice that the origin of both frame and bounds are at 0,0...
I have read numerous pages about frames and bounds, but I don't get it. Any help is appreciated!
The loadimages is called only once.
- (void)loadImages {
sadface = [UIImage imageNamed:#"face-sad.jpg"];
happyface = [UIImage imageNamed:#"face-happy.jpg"];
UIImageView *face1view = [[UIImageView alloc]init];
face1view.image = sadface;
[self.view addSubview:face1view];
CGRect frame;
CGRect contentRect = self.view.frame;
frame = CGRectMake(0, 0, contentRect.size.width, contentRect.size.height);
face1view.frame = frame;
face2view = [[UIImageView alloc]init];
face2view.layer.masksToBounds = YES;
face2view.contentMode = UIViewContentModeScaleAspectFill;
face2view.image = happyface;
[self.view addSubview:face2view];
frame = CGRectMake(startpoint.x, 0, contentRect.size.width, contentRect.size.height);
face2view.frame = frame;
face2view.clipsToBounds = YES;
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint movepoint = [[touches anyObject] locationInView: self.view];
NSLog(#"movepoint: %f %f", movepoint.x, movepoint.y);
face2view.bounds = CGRectMake(0, 0, 320, 480 - movepoint.y);
}
The UIImages and UIImageViews are properly disposed of in the dealloc function.
Indeed, you seem to be confused about frames and bounds. In fact, they are easy. Always remember that any view has its own coordinate system. The frame, center and transform properties are expressed in superview's coordinates, while the bounds is expressed in the view's own coordinate system. If a view doesn't have a superview (not installed into a view hierarchy yet), it still has a frame. In iOS the frame property is calculated from the view's bounds, center and transform. You may ask what the hell frame and center mean when there's no superview. They are used when you add the view to another view, allowing to position the view before it's actually visible.
The most common example when a view's bounds differ from its frame is when it is not in the upper left corner of its superview: its bounds.origin may be CGPointZero, while its frame.origin is not. Another classic example is UIScrollView, which frequently modifies its bounds.origin to make subviews scroll (in fact, modifying the origin of the coordinate system automatically moves every subview without affecting their frames), while its own frame is constant.
Back to your code. First of all, when you already have images to display in image views, it makes sense to init the views with their images:
UIImageView *face1view = [[UIImageView alloc] initWithImage: sadface];
That helps the image view to immediately size itself properly. It is not recommended to init views with -init because that might skip some important code in their designated initializer, -initWithFrame:.
Since you add face1view to self.view, you should really use its bounds rather than its frame:
face1view.frame = self.view.bounds;
Same goes for the happier face. Then in -touchesMoved:… you should either change face2view's frame to move it inside self.view or (if self.view does not contain any other subviews besides faces) modify self.view's bounds to move both faces inside it together. Instead, you do something weird like vertically stretching the happy face inside face2view. If you want the happy face to slide from the bottom of self.view, you should initially set its frame like this (not visible initially):
face2view.frame = CGRectOffset(face2view.frame, 0, CGRectGetHeight(self.view.bounds));
If you choose to swap faces by changing image views' frames (contrasted with changing self.view's bounds), I guess you might want to change both the views' frame origins, so that the sad face slides up out and the happy face slides up in. Alternatively, if you want the happy face to cover the sad one:
face2view.frame = face1view.frame;
Your problem seems to have something to do with the face2view.bounds in touchesMoved.
You are setting the bounds of this view to the rect, x:0, y:0, width:320, height:480 - y
x = 0 == left on the x axis
y = 0 == top on the y axis
So you are putting this image frame at the upper left corner, and making it fill the whole view. That's not what you want. The image simply becomes centered in this imageView.
This is quite the iPhone quandry. I am working on a library, but have narrowed down my problem to very simple code. What this code does is create a 50x50 view, applies a rotation transform of a few degrees, then shifts the frame down a few times. The result is the 50x50 view is now much larger looking.
Here's the code:
// a simple 50x50 view
UIView *redThing = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 50, 50)];
redThing.backgroundColor = [UIColor redColor];
[self.view addSubview:redThing];
// rotate a small amount (as long as it's not 90 or 180, etc.)
redThing.transform = CGAffineTransformRotate(redThing.transform, 0.1234);
// move the view down 2 pixels
CGRect newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height);
redThing.frame = newFrame;
// move the view down another 2 pixels
newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height);
redThing.frame = newFrame;
// move the view down another 2 pixels
newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height);
redThing.frame = newFrame;
// move the view down another 2 pixels
newFrame = CGRectMake(redThing.frame.origin.x, redThing.frame.origin.y + 2, redThing.frame.size.width, redThing.frame.size.height);
redThing.frame = newFrame;
So, what the heck is going on? Now, if I move the view by applying a translation transform, it works just fine. But that's not what I want to do and this should work anyway.
Any ideas?
From the UIView documentation:
If the transform property is also set, use the bounds and center properties instead; otherwise, animating changes to the frame property does not correctly reflect the actual location of the view.
Warning: If the transform property is not the identity transform, the value of this property is undefined and therefore should be ignored.
In other words, I would be wary of the frame property when a transform is set.