UIGestureRecognizer in UIView Object - ios

Question

I have created a UIViewController, which contains a UIView object.
I want the UIView object response to a single tap by 1 finger, and also pinch by 2 fingers.
I have clicked the "User Interaction Enabled" and the "Multiple touch" options in the xib.
I create both UITapGestureRecognizer, and UIPinchGestureRecognizer inside the UIView function initWithFrame:, as it is the only entry point for the UIView object. But the object doesn't response to the UIGestureRecognizer objects. Why? Or, where is the best place to put the UIGestureRecognizer objects?
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
// single tap
UITapGestureRecognizer* singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleSingleTap:)];
singleTap.numberOfTapsRequired = 1;
singleTap.numberOfTouchesRequired = 1;
[self addGestureRecognizer: singleTap];
// 2 fingers pinch
UIPinchGestureRecognizer* doubleMove = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(handleDoubleMove:)];
[self addGestureRecognizer: doubleMove];
}
return self;
}

Answer 1

Your problem is that when you instantiate your custom view subclass in IB, initWithCoder: is called. If you had done it programmatically using initWithFrame: it would have worked properly.
Two ways you can fix this,
Move the gestures setup to a different method and call them in both initWithFrame: and initWithCoder:. I would recommend doing this if you intend to reuse this component and expose some kind of callbacks on gestures.
If you want to implement this once and have a lot of interacting with the controller element, add them in viewDidLoad.

Answer 2

I tried your code and it works for me.
Where are you setting the view? Maybe it has any other view in front, or its superview has userInteractionEnabled disabled.
I created a UIView subclass and added this code:
-(void) handleSingleTap:(UITapGestureRecognizer *)gr {
NSLog(#"handleSingleTap");
}
-(void) handleDoubleMove:(UIPinchGestureRecognizer *)gr {
NSLog(#"handleDoubleMove");
}
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
// single tap
UITapGestureRecognizer* singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleSingleTap:)];
singleTap.numberOfTapsRequired = 1;
singleTap.numberOfTouchesRequired = 1;
[self addGestureRecognizer: singleTap];
// 2 fingers pinch
UIPinchGestureRecognizer* doubleMove = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(handleDoubleMove:)];
[self addGestureRecognizer: doubleMove];
}
return self;
}
Then, in my controller:
-(void) viewDidLoad {
[super viewDidLoad];
MyView * myView = [[MyView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
myView.backgroundColor = [UIColor greenColor];
[self.view addSubview:myView];
[myView release];
}
And it works.

Answer 3

i think if you are working with .xib, initialization can also be done in
-(void)awakeFormNib;

Answer 4

Adding the GestureRecognizers is typically done in the viewDidLoad method of the UIViewController.