Managing events on a custom UIControl

Question

I am subclassing UIControl to compose a custom control that contains different standard controls.

For this discussion let's assume that my custom UIControl contains a UIButton only.

What I would like to achieve is that clicking anywhere in the custom UIControl generates a click event for that custom UIControl. The standard behavior is that the UIButton will process and consume (i.e. not forward) the click event.

As subclassing UIButton is discouraged, I can't really find a straightforward way of achieving this.

Any suggestions?

Answer 1

I came up with a simple solution that doesn't need subclassing of the UIButton.

In the action method defined for the UIButton's TouchUpInside control event, I have added the following line of code:

[self sendActionsForControlEvents:UIControlEventTouchUpInside];

This results in the TouchUpInside control event being called, when clicking anywhere in the custom UIControl.

Answer 2

UIButton is designed to process touch events. You can either set userInteractionEnabled to NO to have the button not accept any touches, or you can use addTarget:action:forControlEvents: on the button to have it call a method on your class when the button is touched.

BTW, where is subclassing UIButton discouraged?

Answer 3

Often I find useful user interaction related tasks in UIResponder class, which is the super class of UIControl - UIButton. Read about – touchesBegan:withEvent:, – touchesMoved:withEvent:, – touchesEnded:withEvent:, – touchesCancelled:withEvent: in http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIResponder_Class/Reference/Reference.html You may find ways to customize user interaction for your UIButton. By the way, I don't think there will be any problem subclassing UIButton, no matter what you've heard, as long as your implementation is correctly added to the super class implementation, or does responsibly override it altogether.

Answer 4

UIViews have a method called -hitTest:withEvent: that the event system uses to crawl the view hierarchy and dispatch events to subviews. If you want a parent view to gobble up all events that might otherwise be dispatched to its subviews, just override the parent's -hitTest:withEvent: with something like the following:

-(UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
  if(CGRectContainsPoint([self bounds], point)){
    return self;
  }
  return [super hitTest:point withEvent:event];
}