Resetting the Zoom on a UIPageViewController - ios

Question

I am building up a simple application that is made up of a UITableViewController with languages and when a specific cell is clicked, a UIPageViewController is brought up to represent the images for that selected language. The user can scroll through the images and everything works as desired. The next step was to build a zooming capability into the UIPageViewController so the user could zoom into the images with a pinch gesture.
I have achieved this with the following code:
- (void)viewDidLoad
{
[super viewDidLoad];
self.leafletImages = [NSMutableArray arrayWithObjects:[[ImageModel alloc] initWithImageName:#"3facts-chinese-page1.jpg"], [[ImageModel alloc] initWithImageName:#"3facts-chinese-page2.jpg"], [[ImageModel alloc] initWithImageName:#"3facts-chinese-page3.jpg"], [[ImageModel alloc] initWithImageName:#"3facts-chinese-page4.jpg"], [[ImageModel alloc] initWithImageName:#"3facts-chinese-page5.jpg"], [[ImageModel alloc] initWithImageName:#"3facts-chinese-page6.jpg"], nil];
// Lots of code for the building up of the UIPageViewController
LeafletImageSizeViewController *imageViewController = [[LeafletImageSizeViewController alloc] init];
imageViewController.model = [_modelArray objectAtIndex:0];
NSArray *viewControllers = [NSArray arrayWithObject:imageViewController];
[self.pageViewController setViewControllers:viewControllers
direction:UIPageViewControllerNavigationDirectionForward
animated:NO
completion:nil];
// Gesture
UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(pinchDetected:)];
[self.view addGestureRecognizer:pinchRecognizer];
pinchRecognizer.delegate=self;
}
The class creating the image and the size is:
- (void)useThreeFactsSize
CGRect insetFrame;
insetFrame = CGRectMake(310, 70, self.view.frame.size.width-615, self.view.frame.size.height-85);
_imageView = [[UIImageView alloc] initWithFrame:insetFrame];
[_imageView setAutoresizingMask:UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight];
[_imageView setImage:[UIImage imageNamed:_model.imageName]];
[[self view] addSubview:_imageView];
[self.view setBackgroundColor:[UIColor clearColor]];
}
The pinchDetection method is:
-(void)pinchDetected:(UIPinchGestureRecognizer *)pinchRecognizer
{
CGFloat scale = pinchRecognizer.scale;
self.pageViewController.view.transform = CGAffineTransformScale(self.pageViewController.view.transform, scale, scale);
pinchRecognizer.scale = 1.0;
}
Now, I can zoom into the images of the UIPageViewController without any issues and it works really well.
What I want to do however is two things:
Not allow the image to be zoomed out beyond the original scale
Create a double tap gesture to bring the image back to it's original scale
With feature 1, the user can zoom into the image, but also completely zoom out of the image which shrinks the image and the UIPageViewController pageIndicators. There's no reason the user should be able to zoom out of the image, so I'd like to allow the user to zoom in to any scale, but not to zoom out beyond what the original size of the image on screen in the UIPageViewController.
With feature 2, I'd like to implement a gesture to double tap the screen and for the zoomed image to go back to it's original scale (like the Photos.app).
Update
With reference to the answer, I have updated the question to reflect how I'm going about doing the images. With point 2 and the double tap gesture, the following code almost works:
- (void)scrollViewTwoFingerTapped:(UITapGestureRecognizer *)recognizer
{
NSLog(#"Double Tap");
self.pageViewController.view.transform = CGAffineTransformIdentity;
}
What it's currently doing is if I zoom in with a pinch and pan around, and then double tap, it centres the image to the point of where I tapped, so sometimes the borders are being shown, etc, rather than making the image centre to where it's supposed to be.
For point 1:
if (pinchRecognizer.scale > 1) {
CGFloat scale = pinchRecognizer.scale;
self.pageViewController.view.transform = CGAffineTransformScale(self.pageViewController.view.transform, scale, scale);
pinchRecognizer.scale = 1.0;
}
If I have self.imageview, it doesn't work because it's nil and even if I make a call to the class setting the size, it's nil as well.
I suspect I have a number of things wrong with my code!
For reference, I have panning working with:
- (void)panGestureDetected:(UIPanGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];
if (state == UIGestureRecognizerStateBegan || state == UIGestureRecognizerStateChanged)
{
CGPoint translation = [recognizer translationInView:recognizer.view];
[recognizer.view setTransform:CGAffineTransformTranslate(recognizer.view.transform, translation.x, translation.y)];
[recognizer setTranslation:CGPointZero inView:recognizer.view];
}
else if(state==UIGestureRecognizerStateEnded){
UIView *imageView = recognizer.view;
UIView *container = imageView.superview;
CGFloat targetX = CGRectGetMinX(imageView.frame);
CGFloat targetY = CGRectGetMinY(imageView.frame);
if(targetX>0){
// targetX = 0;
}else if(CGRectGetMaxX(imageView.frame)<CGRectGetWidth(container.bounds)){
targetX = CGRectGetWidth(container.bounds)-CGRectGetWidth(imageView.frame);
}
if(targetY>0){
// targetY = 0;
}else if(CGRectGetMaxY(imageView.frame)<CGRectGetHeight(container.bounds)){
// targetY = CGRectGetHeight(container.bounds)-CGRectGetHeight(imageView.frame);
}
// imageView.frame = CGRectMake(targetX, targetY, CGRectGetWidth(imageView.frame), CGRectGetHeight(imageView.frame));
[UIView animateWithDuration:0.3 animations:^{
imageView.frame = CGRectMake(targetX, targetY, CGRectGetWidth(imageView.frame), CGRectGetHeight(imageView.frame));
}];
}
}
That's working very well at the moment, but there's definitely a conflict with everything else.
I'd really appreciate any guidance in the right direction on this.

Answer 1

1.) To not allow the image to be zoomed out beyond it's original scale you first just need to check if the scale you're about to set it to is greater than 1 or not. If it's less than one, you don't want to rescale your image as that would mean it gets smaller. So...
#IBAction func doPinch(sender: UIPinchGestureRecognizer) {
if sender.scale > 1 {
let transform = CGAffineTransformMakeScale(sender.scale, sender.scale)
imageView.transform = transform
}
}
2.) You seem to be changing the view's frame to try and change it's scale, but you never adjusted the view's frame yourself in the first place. You're adjusting the view's transform. That means in order to return it to it's original size you must remove whatever transform you put on it. To do this you put it back to it's identity. So...
#IBAction func doDoubleTap(sender: UITapGestureRecognizer) {
imageView.transform = CGAffineTransformIdentity
}
My code samples are in Swift but you should be able to adjust it to Objective-C yourself. Also, you seem to be adjusting the transform/scale of the entire page view itself. I would suggest you change the scale of only the image view. That makes more sense as that's actually what you're trying to zoom into.