I have a UIPanGestureRecognizer attached to a map view in my window (and recognizing gesture simulateously so I can receive events when the map pans). However for some reason I can't figure out, [UIPanGestureRecognizer translationInView:] always returns coordinates relative to the origin of the pan. In fact it behaves identically regardless of what view parameter I pass to it, even nil!
I can't figure out why it's not telling me coordinates relative to the view I pass in.
self.mapViewPan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(pan:)];
self.mapViewPan.delegate = self;
[self.mapView addGestureRecognizer:self.mapViewPan];
*
- (void)pan:(UIPanGestureRecognizer*)sender {
CGPoint translatedPoint = [sender translationInView:self.view];
NSLog(#"%f, %f", translatedPoint.x, translatedPoint.y);
}
Nevermind, I seem to have misunderstood what translationInView: actually represents. It appears to be relative to the origin of the touch regardless (which makes me wonder what its parameter actually affects).
It turns out what I really want is locationInView::
CGPoint touchPoint = [sender locationInView:self.view];
This returns the location of the touch in the view's coordinates.
Is there any reason you're not using the MKMapViewDelegate methods for this?
mapView:regionDidChangeAnimated: should let you get the map region when it scrolls.
Related
I am working on an iOS map app and it includes interactive map. The interactive map is a subclass of UIImageView and placed on a scrollView. My view hierarchy is shown below:
When user taps some part of the map, ViewController performs animated segue (like zoom-in to that area of the map). I can start segue from any point of the screen, but to do this properly, I need exact coordinates of user's tap relative to the screen itself. As ImageView is put at the top of ScrollView, it uses different coordinate system, larger than screen size. No matter, which area of map has ben tapped, what matters is the tapped CGPoint on the screen (physical).
ImageView uses its own code to get coordinates of a tap:
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[super touchesEnded:touches withEvent:event];
// cancel previous touch ended event
[NSObject cancelPreviousPerformRequestsWithTarget:self];
CGPoint touchPoint = \
[[touches anyObject] locationInView:self];
NSValue* touchValue =\
[NSValue
valueWithCGPoint:touchPoint];
// perform new one
[self
performSelector:#selector(_performHitTestOnArea:)
withObject:touchValue
afterDelay:0.1];
}
And the case if I place gesture recognizer, it works, but ImageView can't get any touches and, therefore, call segue.
The code for gesture recognizer, I attempted to use:
UITapGestureRecognizer *rec = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(tapRecognized:)];
[someView addGestureRecognizer:rec];
[rec release];
// elsewhere
- (void)tapRecognized:(UITapGestureRecognizer *)recognizer
{
if(recognizer.state == UIGestureRecognizerStateRecognized)
{
CGPoint point = [recognizer locationInView:recognizer.view];
// again, point.x and point.y have the coordinates
}
}
So, is there any way to get two coordinates in different reference systems?, or to make these recognizers work simultaneously without interfering each other?
Solved
I use this code to convert touched point from one view's reference system to
CGPoint pointInViewCoords = [self.parentView convertPoint:self.imageView.touchPoint fromView:self.imageView];
Where self.parentView is "View" on hierarchy image - with the size of the screen.
How would you properly determine if a point is inside a rotated CGRect/frame?
The frame is rotated with Core Graphics.
So far I've found an algorithm that calculates if a point is inside a triangle, but that's not quite what I need.
The frame being rotated is a regular UIView with a few subviews.
Let's imagine that you use transform property to rotate a view:
self.sampleView.transform = CGAffineTransformMakeRotation(M_PI_2 / 3.0);
If you then have a gesture recognizer, for example, you can see if the user tapped in that location using locationInView with the rotated view, and it automatically factors in the rotation for you:
- (void)handleTap:(UITapGestureRecognizer *)gesture
{
CGPoint location = [gesture locationInView:self.sampleView];
if (CGRectContainsPoint(self.sampleView.bounds, location))
NSLog(#"Yes");
else
NSLog(#"No");
}
Or you can use convertPoint:
- (void)handleTap:(UITapGestureRecognizer *)gesture
{
CGPoint locationInMainView = [gesture locationInView:self.view];
CGPoint locationInSampleView = [self.sampleView convertPoint:locationInMainView fromView:self.view];
if (CGRectContainsPoint(self.sampleView.bounds, locationInSampleView))
NSLog(#"Yes");
else
NSLog(#"No");
}
The convertPoint method obviously doesn't need to be used in a gesture recognizer, but rather it can be used in any context. But hopefully this illustrates the technique.
Use CGRectContainsPoint() to check whether a point is inside a rectangle or not.
Essentially, what I want to do is to move a view around to follow the user's pan. This works fine as long as the same pan object is being used. The problem comes when the user releases and than starts another pan.
According to the documentation, the value in translationInView is relative to the position at the start of the pan.
So my strategy for handling this was to add two properties to my view so I can tell whether the same pan object is being used and what the reference location is. The self object is the object being moved. It is a UIView subclass.
CGPoint originalPoint;
if (pan == self.panObject) {
//If the pan object is the same as the one in the property, use the saved value as the reference point.
originalPoint = CGPointMake(self.panStartLocation.x, self.panStartLocation.y);
} else {
//If the pan object is DIFFERENT, set the originalPoint from the existing center.
//self.center is in self.superview's coordinate system.
originalPoint = CGPointMake(self.center.x, self.center.y);
self.panStartLocation = CGPointMake(originalPoint.x, originalPoint.y);
self.panObject = pan;
}
CGPoint translation = [pan translationInView:self.superview];
self.center = CGPointMake(originalPoint.x+translation.x, originalPoint.y+translation.y);
This scheme doesn't work because each pan object apparently is the same object. I've spent a bit of time in the debugger verifying this, and that seems to be true. I thought the pan object would be different for each touch. So since this doesn't work, what is the alternative?
I solved it. Here is the corrected code:
CGPoint originalPoint;
if (pan.state == UIGestureRecognizerStateBegan) {
originalPoint = CGPointMake(self.center.x, self.center.y);
self.panStartLocation = CGPointMake(originalPoint.x, originalPoint.y);
} else {
originalPoint = CGPointMake(self.panStartLocation.x, self.panStartLocation.y);
}
CGPoint translation = [pan translationInView:self.superview];
self.center = CGPointMake(originalPoint.x+translation.x, originalPoint.y+translation.y);
EDIT: A better approach is to take advantage of the fact that the gesture recognizer allows you to set the translation:
[sender setTranslation:CGPointMake(0.0, 0.0) inView:self.pieceBeingMoved];
Do this when you move your item, and then the new translation next time will be relative to the position you just moved to.
UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(pan:)];
[self addGestureRecognizer:panRecognizer];
- (void)pan:(UIPanGestureRecognizer *)gesture {
NSLog(#"%f", [gesture translationInView:self].x);
}
The above code will log the relative position of my current pan, but how can I get the absolute position for the view I'm in?
I'm simply just wanting to slide a UIImageView to wherever the user's finger is.
translationInView gives you the pan translation (how much x has changed) and not the position of the pan in the view (the value of x). If you need the position of the pan, you have to use the method locationInView.
You can find the coordinates relatively to the view as follows:
- (void)pan:(UIPanGestureRecognizer *)gesture {
NSLog(#"%f", [gesture locationInView:self].x);
}
Or relatively to the superview:
- (void)pan:(UIPanGestureRecognizer *)gesture {
NSLog(#"%f", [gesture locationInView:self.superview].x);
}
Or relatively to the window:
- (void)pan:(UIPanGestureRecognizer *)gesture {
NSLog(#"%f", [gesture locationInView:self.window].x);
}
Swift 5
Use the method .location() that returns a CGPoint value. [documentation]
For example, relative location of your gesture to self.view:
let relativeLocation = gesture.location(self.view)
print(relativeLocation.x)
print(relativeLocation.y)
I think a simple way of something like this is to get the x and y of the touch and tracking it, once it has 2 points (say X:230 Y:122) you set the scroll of the UIScroll view to the x and y.
I have an image that I would like to set up to respond to several different gesture responders. So for example, if one part of the picture is touched I would like one selector to be called, and another selector for a different part of the picture.
I looked at the UIGestureRecognizer and UITapGestureRecognizer classes, but I couldn't find a way to specify the image zones to be associated with them. Is this at all possible in iOS? And if so what classes should I look into using?
The easiest solution is to lay invisible views over the image and put the gesture recognizers on them.
If that's not feasible you'll have to look at the locationInView in the gesture recognizer's tap handler and figure out what you want to do based on where the user tapped.
Use the locationInView: property to determine where your tap occurred and then conditionally invoke a method. You can do this by setting up some CGRects that correspond to your hit areas. Then use the CGRectContainsPoint() function to determine if the tap landed in one of the hit areas.
Your tap gesture recognizer action may look something like this:
- (void)tapGestureRecognized:(UIGestureRecognizer *)recognizer
{
// Specify some CGRects that will be hit areas
CGRect firstHitArea = CGRectMake(10.0f, 10.0f, 44.0f, 44.0f);
CGRect secondHitArea = CGRectMake(64.0f, 10.0f, 44.0f, 44.0f)
// Get the location of the touch in the view's coordinate space
CGPoint touchLocation = [recognizer locationInView:recognizer.view];
if (CGRectContainsPoint(firstHitArea, touchLocation))
{
[self firstMethod];
}
else if (CGRectContainsPoint(secondHitArea, touchLocation))
{
[self secondMethod];
}
}