enable pinch to zoom in viewcontroller - ios

Question

I want users to be able to use pinch to zoom in my app which uses Storyboard and programmatically generated buttons and labels to produce a View within a Viewcontroller. In the View's Attribute inspector I have checked both User Interaction Enabled and Multiple Touch. But no pinch to zoom seems to work.
The code which creates the important part of the View is as follows.
- (void)viewDidLoad
{
[super viewDidLoad];
NSInteger xPipsOrigin = 0;
NSInteger xPipsStep = 22.0;
NSString* cards = #"AKQJT98765432";
NSInteger yPipsOrigin = 100;
if (UI_USER_INTERFACE_IDIOM()== UIUserInterfaceIdiomPhone){
xPipsOrigin = 0;
xPipsStep = 22.0;
xPipsStep = 34.0;
}
else{
xPipsOrigin = 100;
xPipsStep = 40.0;
}
NSInteger xPipsCurrent = xPipsOrigin;
self.countCards = 0;
self.cardList = [NSMutableArray arrayWithCapacity:0];
yPipsOrigin = 100;
xPipsCurrent = xPipsOrigin;
for( int x=0;x<[cards length]; x++ ){
[cards substringWithRange:NSMakeRange(x,1)];
UIButton *b= [UIButton buttonWithType:UIButtonTypeRoundedRect];
xPipsCurrent += xPipsStep;
[b setTitle:[cards substringWithRange:NSMakeRange(x,1)] forState:UIControlStateNormal];
[b setTitle:#" " forState:UIControlStateDisabled];
[b setFrame:CGRectMake(xPipsCurrent, yPipsOrigin, 20, 20)];
[b setEnabled:YES];
[b setUserInteractionEnabled:YES];
[self.view addSubview:b];
[b addTarget:self action:#selector(spadeButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
}
xPipsCurrent = xPipsOrigin + xPipsStep/2;
for( int x=0;x<[cards length]-1; x++ ){
xPipsCurrent += xPipsStep;
UILabel *lab = [[UILabel alloc] initWithFrame:CGRectMake( 0, 0, 20, 20)];
lab.text = #"\u2660";
lab.backgroundColor = [UIColor clearColor];
lab.center = CGPointMake(xPipsCurrent+10, yPipsOrigin+10);
[self.view addSubview:lab];
}
}
How can I enable Pinch to Zoom in this app?

Answer 1

If you want to enable pinch to zoom on a UIView you have to wrap it into a UIScrollView first

Answer 2

Whilst you can use User Interaction Enabled and try do it that way, it'll be easier to add a UIGestureRecogniser to your UIView. That way it handles most of the setup code for you, and when it detects a pinch triggers a method.
Basic example in Objective-C:
UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(handlePinchGesture:)];
[self.view addGestureRecognizer:pinchGesture];
- (void)handlePinchGesture:(id)sender
{
NSLog(#"Recieved pinch");
UIPinchGestureRecognizer *senderGR = (UIPinchGestureRecognizer *)sender;
NSLog(#"Scale is: %f", senderGR.scale);
}
And in Swift:
let pinchGestureRecognizer = UIPinchGestureRecognizer.init(target: self, action: #selector(ViewController.handlePinchGesture(_:)))
self.view.addGestureRecognizer(pinchGestureRecognizer)
func handlePinchGesture(sender:AnyObject) {
print("Received pinch")
let senderGR = sender as! UIPinchGestureRecognizer
print("Scale is \(senderGR.scale)")
}