Question

Objective: To get a UIView, which is a small magnifying glass, to be placed above the navigation controller. It’s exactly like the loupe in the Notes program.

I have partly accomplished this task with the following code:

MyAppDelegate *app = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
[[[[app navigationController] view] superview] addSubview:_loupe];

This allows the loupe to be displayed above the navigation controller. Note: The _loupe variable contains an instance of a UIView that will magnify the view.

This code works perfectly when in Portrait. When I change the orientation to Landscape, however, the coordinates of the _loupe appear to still be in portrait mode.

Through lots of trial and error and hours of head banging I realized that the UINavigationController, which is added as the rootViewController of the application, never updates its coordinates when the orientation changes. ALL other views, including the RootViewController (the default class created when creating a new application in XCode) has their coordinates updated.

I tried to rectify this by subclassing the UINavigationController with my own controller to make it so the shouldAutorotateToInterfaceOrientation: gets called by the navigation controller instead of the RootViewController. I was hoping that the reason it didn’t rotate is because it wasn’t the controller requesting the orientation. Nothing.

I’ve also rotated the _loupe view with the following:

CGAffineTransform transform = _loupe.transform;
transform = CGAffineTransformMakeRotation([self degreesToRadians:90.0]);
_loupe.transform = transform;
_loupe.bounds = CGRectMake(0, 0, 480, 320);
_loupe.frame = CGRectMake(0, 0, 80, 80);

This makes the UIView, underneath the touch, magnified right side up. Originally, the UIView underneath was rotated -90 when changing the orientation to the left. So I’m almost there… but the coordinates are still screwed up.

I’ve also tried changing the _loupe.bounds to CGRectMake(0, 480, 480, 320) believing that changing the origin might match the underlying coordinate system. No dice.

My last resort was doing a transform on the actual UITouch x/y points.

    CGPoint point = [touch locationInView:self];
    CGAffineTransform transform = CGAffineTransformRotate([_loupe transform], [self degreesToRadians:90.0]);
    CGPoint tPoint = CGPointApplyAffineTransform(point, transform);

No dice. However, this does make the loupe displayed near the visible area. What I’m finding is that moving the touch on the x axis moves the loupe on the y axis and moving the touch on the y axis moves the loupe on the x axis. So now it’s completely inverted.

In short, I just want an easy way to display a magnifying glass above the navigation controller without all of this rigmarole.

Edit

I got a little closer by converting the point to the loupe’s view.

CGPoint tPoint = [self convertPoint:point toView:_loupe];

This makes the loupe flicker a lot… it also appears to move the loupe on both the x & y axis (vertically) no matter the direction I move the touch. Getting much closer though!

Answer 1

Resolution

This is it:

CGPoint tPoint = [self convertPoint:point toView:[[[app navigationController] view] superview]];

All I had to do was convert the CGPoint, created from the UITouch event, to that of the coordinate space of the navigation controller’s superview (which the loupe is part of).