Question

I am trying to detect touches inside a subview

In my main viewcontroller I am adding a subview called:SideBarForCategory, it takes 30% of the screen from the left – as a sidebar.

SideBarForCategory *sideBarForCategory = [[SideBarForCategory alloc] initWithNibName:@"SideBarForCategory" bundle:nil];  
[sideBarData addSubview:sideBarForCategory.view];

inside SideBarForCategory, I would like to test for touches

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event touchesForView:self.view] anyObject];

    CGPoint location = [touch locationInView:touch.view];
    NSLog(@"Map Touch %f",location.x);

}

The above code (touchesMoved) works perfectly on the main view (viewcontroller) but does not work inside my subview (SideBarForCategory) – why and how can I fix it?

Answer 1

Two possible solutions i can think of :

1. Either use GestureRecognizers (eg. UITapGestureRecognizer, UISwipeGestureRecognizer) and add those recognizers to your SideBarForCategory view.

2. Generic gesture handling : Create your own custom subclass of UIView for example MyView and add those touch methods inside it. Then create SideBarForCategory view as an instance of MyView.

Hope it works 🙂

Updated :
For second option :

#import <UIKit/UIKit.h>

@interface MyView : UIView
@end





@implementation MyView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
  // No need to invoke |touchesBegan| on super
  NSLog(@"touchesBegan");
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
  // invoke |touchesMoved| on super so that scrolling can be handled
  [super touchesMoved:touches withEvent:event];
  NSLog(@"touchesMoved");
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
  [super touchesEnded:touches withEvent:event];
  NSLog(@"touchesEnded");
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
  /* no state to clean up, so null implementation */
  NSLog(@"touchesCancelled");
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

@end

Update :
And then in your SideBarCategoryView class implementation , inside loadView()

self.view = [[MyView alloc] init];