Solve the viewController sizing mystery! Why do elements (UIImageView and Nav bar) change size when switching viewControllers? - ios

Question

So this is the code for my mapView:
self.mapView = [[MKMapView alloc] init];
self.mapView.frame = CGRectMake(0, 70 , self.view.bounds.size.width,
self.view.bounds.size.height);
When I push to this view controller from one viewcontroller it looks just fine. The navigation bar and map view are all in the correct spot; however, when I tried to create a button that go directly to the map Viewcontroller from ANOTHER viewController everything changed.
The map view has shrunk and the navigation bar is missing now..? Here's the new button from the other ViewController:
UIImage* image4 = [UIImage imageNamed:#"Near_me_carousel.png"];
_mapButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 18, 26, 26)];
[_mapButton setBackgroundImage:image4 forState:UIControlStateNormal];
[_mapButton addTarget:self action:#selector(MapButton)
forControlEvents:UIControlEventTouchUpInside];
[_mapButton setShowsTouchWhenHighlighted:YES];
[self.view addSubview:_mapButton];
Here's the method:
-(void) MapButton {
MapViewController *mapView = [[MapViewController alloc] init];
[self.navigationController presentViewController:mapView animated:YES completion:NULL];
}
I'm so confused as to why this is happening! Any ideas?

Answer 1

I don't know if this is really your problem, but here's a shot:
Inside your button method, you are calling your MapViewController modally. If the viewController itself does not have a UINavigationBar, of course it will not be displayed.
When you have a push transition, through a UINavigationController, a navigationBar is automatically added above of your view.
And here's the tricky part: when presented as a push transition, the 0 y value of the view's frame is the point just below the navigationBar. I. e., the navigationBar does not belong to your view.
And when presented through a modal transition (presentViewController:), the 0 y value is the top/left point of the window, even if you add a NavigationBar yourself.
Ilustrating:
The origin of it will be here if presented as a modal:
And here if presented if a push in a navigation stack:
Conclusion:
So, in your case, the y-value 70 in this code
self.mapView.frame = CGRectMake(0, 70 , self.view.bounds.size.width,
self.view.bounds.size.height);
will be different according to the transition style. In a modal, it will look like it's displaced 44 points to the top (size of the navigation bar)