is there a way to update (i.e. moving around) a MKOverlay that is already added to the MKMapView. Removing a old one and adding a new one is terrible (slow).
i.e i would like to trigger the background function that is calling this function when an overlay moves on the screen:
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
(with MKAnnotions its a little better i think, but i cant use MKPolyline, MKPolygon, etc. and the whole information is reduced to a single point)
MKOverlayView has the following methods which force MapKit to re-render the given mapRect:
- (void)setNeedsDisplayInMapRect:(MKMapRect)mapRect
- (void)setNeedsDisplayInMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale
If you’re using a timer (or periodical HTTP request or some sort of other method for determining that your overlay should be updated), calling one of the above methods on the overlayView will cause it to re-render that spot on the map (i.e. -canDrawMapRect:zoomScale: will be called again, and then -drawMapRect:zoomScale:inContext: will be called if the former returns YES).
Update:
If you’re not sure what mapRect you need to re-render, you might be able to use the MKMapRectWorld constant as the mapRect — which I believe would cause the overlay across the entire map to reload (once visible).
Use MKAnnotations. You can change the coordinate of them. Just disable any touch-related stuff. You would need your own drawing code to draw the annotations, OpenGL would probably do the trick. Nobody would know the difference.
I actually had to force the overlay view to invalidate the path, to clear out the old path before setting up a new one. [polygonView invalidatePath]. Telling the map view that it needs a display refresh was insufficient for me.
This seems to force the map to refresh overlays. Probably annotations as well.
[self.mapView setCenterCoordinate:self.mapView.centerCoordinate];
Swift 3+ update, this worked for me, thanks #zenchemical for the inspiration.
DispatchQueue.main.async {
self.map.add(overlay, level: .aboveRoads)
self.map.setCenter(self.map.centerCoordinate, animated: false)
}
Side note, I can't help feeling that this shouldn't be necessary and there is a more appropriate solution, however, I haven't found it. Even though the add command is dispatched to the main queue, the overlay reproducibly does not render until I move the map.
there is a problem with raw setNeedsDisplay if the bounding rectangle of the polygon changes then MKMapView would not update whole rectangle correctly,and secondly,MKPolygon/MKPolygonRenderer's polygon is not updatable,and the problem with add/remove pipeline is if there is too much request to update the MapView it can get slower in the pipeline, I currently use a 30Hz thread loop if there is an update in polygon i do add/remove
Related
i have UISwipeGestureRecognizer that detects if the user has swiped. i also draw the users touches using the touches moved method found in the tutorial below.
http://www.ifans.com/forums/showthread.php?t=132024
My issue is the gesture seems to override my drawing. is it possible to do both or is there a better way of doing this?
Thanks
Dan
All of the touches methods get overridden when you invoke a gestureRecognizer. You can view it here in the explanation. It may be best to just write your own code to recognize a gesture if you need all of the touch events for drawing updates. If you still want to use a gestureRecognizer, you can use the locationInView: method to find the location of the touch, and then pass those points to your draw method.
I would also think about using OpenglES instead, as it isa bit easier, and you can do more things. There's a great sample project about it here. Hope that helps!
I'm currently using CADisplayLink to show an OpenGL animation which works great. Sometimes, however a parameter changes and I need to redraw the view immediately and can't wait until the next frame is requested by CADisplayLink. If I don't do that, I get one frame wrong which looks really bad in my case.
So, how can I force a redraw of an EAGLView without interfering with the CADisplayLink stuff?
If your CADisplayLink is calling method drawFrame, for example, then just call drawFrame yourself when you need to. No reason you need to wait for CADisplayLink if you don't want to.
Your question suggests that you're storing your data in your view rather than in a data object. You should be able to change your data at any time, and your view should update when its needed to display. Move the data to a model object, and have the EAGLView draw itself based on the data when requested from the CADisplayLink rather than redrawing itself when the data changes.
I'm trying to detect animations and other screen updates as they happen inside a UIWebView. I would like to get the rectangles of areas in the UIWebView that have been modified since the last refresh.
I think really what I'm looking for is for a way to "trap" the calls that UIWebView makes to setNeedsDisplayInRect. Is there a way to do that? Can I somehow subclass UIWebView's underlying CALayer object in a way that would allow me to catch those calls as they come in from UIWebView?
There's no good way of doing that. You can try grabbing a snapshot of the UIWebView's CALayer and comparing it to the previous snapshot, but I've had a lot of trouble getting reliable snapshots of UIWebViews.
Use an Objective-C category (#implementation CALayer (MyCALayer)) - like you're already doing based on your update - to trap the calls going from UIWebView to CALayer.
Then, use Method Swizzling to relay your category overrides to the original CALayer object.
I have a Map View defined in IB and it is set to show the user location.
In my app, in -viewDidAppear, I query self.mapView.userLocation.location.coordinate and it comes back with insane values such as:
latitude: 4.8194501961644877e-49
longitude: 2.2993313035571993e-59
However, the next time -viewDidAppear is called (after I've simply moved to another tabbed view and then back to this one) the userLocation property holds exactly the correct values for my current location.
It seems that at the time of my initial call, the userLocation property has not been initialised but despite having read Apple's documentation I can't see any caveats where it says that this property is only valid after doing xxx.
Is there something that has to happen before userLocation is valid to use or should I just use CLLocationManager and ask it instead?
Thanks in advance for any help.
Sadly, Thomas' suggestion didn't help. What I have since discovered is:
If showsUserLocation is NO, then userLocation is never set correctly and -MapView:didUpdateUserLocation: is never called, consequently I never ever get a sensible location value.
So, to get the user's location I have to set showsUserLocation to YES, however that then means that after all my annotations have been added to the view (without including the user's location) I then calculate the required span to encompass them all and display them all at the right zoom level. After I do that though, the view jumps sideways as the Map View then automatically displays the user's location as the blue blob! As it was never included in the annotations to work out the zoom level I can't incorporate it into my calculations. Aaargh!
Note that when showsUserLocation is YES, then -MapView:didUpdateUserLocation: is called, but only after I've calculated all the coordinates of my annotations, not before!
I'm assuming it hasn't finished finding the user location - it has to work this out and it may take a while.
Instead of using it in viewDidLoad use THIS delegate method:
- (void)mapView:(MKMapView *)myMapView didUpdateUserLocation:(MKUserLocation *)userLocation;
You will need to set your mapview delegate to self. :)
Same is often true of Core Location. You'll get the last location lingering it its buffer, sometimes, or a super-broad throw-the-dart-at-the-map kind of location...
Best bet is to check the .horizontalAccuracy property of the location object and toss any that are too vague. It's good practice to just chuck the first one too.
for didUpdateUserLocation to be called you have to have...
mapView.showsUserLocation = TRUE;
I'm displaying a MKMapView with MKAnnotations some of which are selected and showing their Annotation.
I am trying to grab an image of the displayed map and annotations using the -renderInContext.
90% of the time the Map, MKPinAnnotationView's and selected annotations are correctly captured.
The other 10% of the time the image is missing something, usually the MKPinAnnotationViews or their annotations if selected.
I've added code to deal with the Map itself loading it's map data.
But I haven't been able to track down something that would indicate to me that all of the visible MKPinAnnotationView's have been drawn
and if selected their annotations displayed??
the closest hint I've come across is the addObserver, although I haven't figured out what could be observed that would tell me when all of the drawing is done.
Thoughts?
ok I'm an idiot...
I finally tracked down the problem. In my viewForAnnotation routine in the MKMapView Delegate protocol I wasn't correctly setting values for reused MKPinAnnotationView's.
So some of the time I would reuse a view that had .canShowCallout set to YES and other times I'd reuse a view that had .canShowCallout set to NO.
.<
Try using the MKMapViewDelegate didAddAnnotationViews method.
If in that method, the drawing is still not ready for your requirements, you could then in there call your capturing method with performSelector:withObject:afterDelay:.