UIScrollView SetZoomScale not work - ios

Question

after read some other cuestions about it i've tried:
on ViewController.m
DelegateScrollView ScrollView;
-(void)viewDidLoad
{
[super viewDidLoad];
ScrollView = [[DelegateScrollView alloc] initWithFrame:CGRectMake(0,- self.view.frame.size.height, self.view.frame.size.width, self.view.frame.size.height)];
ScrollView.delegate = ScrollView;
ScrollView.scrollEnabled = YES;
ScrollView.backgroundColor = [UIColor blackColor ];
ScrollView.maximumZoomScale = 5.0f;
ScrollView.minimumZoomScale = 1.0f;
[self.view addSubview:ScrollView];
[ScrollView setZoomScale:2 animated:YES];
}
DelegateScrollView.h:
#interface ChildDelegateScrollView : UIScrollView <UIScrollViewDelegate>
#end
and zoom never happends also i've tried this in ViewController.h: #interface ViewController : UIViewController <UIScrollViewDelegate> then set delegate like this ScrollView.delegate = self; and not work, how is the way to set correctly a delegate to a ScrollView?

Answer 1

This line from the UIScrollView class reference seems to be relevant:
For zooming and panning to work, the delegate must implement both viewForZoomingInScrollView: and scrollViewDidEndZooming:withView:atScale:
I was able to get a UILabel on a UIScrollView to zoom using this UIViewController code:
#import "ViewController.h"
#interface ViewController () <UIScrollViewDelegate> {
UIScrollView *_scrollView;
}
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0, 0.0, self.view.frame.size.width, self.view.frame.size.height)];
scrollView.delegate = self;
scrollView.scrollEnabled = YES;
scrollView.backgroundColor = [UIColor blackColor];
scrollView.maximumZoomScale = 5.0f;
scrollView.minimumZoomScale = 1.0f;
scrollView.contentSize = CGSizeMake(scrollView.frame.size.width, scrollView.frame.size.height);
[self.view addSubview:scrollView];
_scrollView = scrollView;
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(50.0, 50.0, 100.0, 25.0)];
label.backgroundColor = [UIColor grayColor];
label.textAlignment = NSTextAlignmentCenter;
label.text = #"Test";
[_scrollView addSubview:label];
}
- (void)viewDidAppear:(BOOL)animated
{
[_scrollView setZoomScale:4.0 animated:YES];
}
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return _scrollView.subviews.firstObject;
}
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
}
#end