Constrain cameraOverlayView to center of screen

Question

I'm using zBAR QR Reader in an iPad app im creating and I've added a custom crosshair overlay to the ZBarReaderViewController . I've managed to get the overlay into the center, however when the device rotates, the overlay obviously goes off center.

I've had a search around in regards to programmatically constraining the view but none of the suggestions have worked. I've tried every possible combination with UIViewAutoResizingMask and I've tried heaps of different setups with the [NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:] method.

Here's my code:

self.readerqr = [ZBarReaderViewController new];

int readerPointX = ((self.view.bounds.origin.x) + (self.view.bounds.size.width / 2.0));
int readerPointY = ((self.view.bounds.origin.y) + (self.view.bounds.size.height / 2.0) -60);

self.readerqr.readerDelegate = self;
self.readerqr.showsHelpOnFail = NO;

CGRect viewFrame = CGRectMake(readerPointX, readerPointY, 200, 200);

self.crossHair = [[UIImageView alloc] initWithFrame:viewFrame];

self.crossHair.image = [UIImage imageNamed:@"qr.png"];

[self.readerqr setCameraOverlayView:self.crossHair];

constraint = [NSLayoutConstraint constraintWithItem:self.crossHair
                                          attribute:NSLayoutAttributeHeight
                                          relatedBy:NSLayoutRelationEqual
                                             toItem:nil
                                          attribute:NSLayoutAttributeNotAnAttribute
                                         multiplier:1
                                           constant:200];

[self.crossHair addConstraint:constraint];

constraint = [NSLayoutConstraint constraintWithItem:self.crossHair
                                          attribute:NSLayoutAttributeWidth
                                          relatedBy:NSLayoutRelationEqual
                                             toItem:nil
                                          attribute:NSLayoutAttributeNotAnAttribute
                                         multiplier:1
                                           constant:200];
[self.crossHair addConstraint: constraint];

What is the proper way to set this up so my overlay will always be in the center of the screen regardless of orientation change? Any help would be great, thanks.

Answer 1

This question might not be relevant anymore, but still hope this code helps someone. First of all, when using autolayout you do not need to deal with frames. Secondly, try this code

self.readerqr = [ZBarReaderViewController new];

self.readerqr.readerDelegate = self;
self.readerqr.showsHelpOnFail = NO;

self.crossHair = [[UIImageView alloc] init];
self.crossHair.translatesAutoresizingMaskIntoConstraints = NO;
self.crossHair.image = [UIImage imageNamed:@"qr.png"];

[self.readerqr setCameraOverlayView:self.crossHair];

[self.readerqr addConstraint:[NSLayoutConstraint constraintWithItem:self.crossHair
                                                          attribute:NSLayoutAttributeHeight
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:nil
                                                          attribute:NSLayoutAttributeNotAnAttribute
                                                         multiplier:1
                                                           constant:200]];

[self.readerqr addConstraint: [NSLayoutConstraint constraintWithItem:self.crossHair
                                                           attribute:NSLayoutAttributeWidth
                                                           relatedBy:NSLayoutRelationEqual
                                                              toItem:nil
                                                           attribute:NSLayoutAttributeNotAnAttribute
                                                          multiplier:1
                                                            constant:200]];

[self.readerqr addConstraint:[NSLayoutConstraint constraintWithItem:self.crossHair
                                                          attribute:NSLayoutAttributeCenterX
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.readerqr
                                                          attribute:NSLayoutAttributeCenterX
                                                         multiplier:1
                                                           constant:0]];
[self.readerqr addConstraint:[NSLayoutConstraint constraintWithItem:self.crossHair
                                                          attribute:NSLayoutAttributeCenterY
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.readerqr
                                                          attribute:NSLayoutAttributeCenterY
                                                         multiplier:1
                                                           constant:0]];