How can I make an unclipped subview receive touch events?

Question

I have a small custom view that I use as a button. I make this happen with a simple UIButtonTypeCustom , which I include as a subview over the bounds of the view. Since the view is small, however, I want to increase the size of the hit target. This is easily done (one would think) by setting the frame of my button to be larger than the bounds of the custom view and setting clipsToBounds to NO. This works for the visual (the custom button draws outside the parent view) but it does not receive touchUpInside events on the area outside of the parent view. How do I make the button receive touchUpInside events?

- (id) initWithFrame: (CGRect) frame {
  if (self = [super initWithFrame: frame]) {
    self.backgroundColor = [UIColor clearColor];
    self.clipsToBounds = NO;

    // ... various image views and labels ...

    UIButton *touchArea = [UIButton buttonWithType: UIButtonTypeCustom];
    touchArea.backgroundColor = [UIColor colorWithRed: 1 green: 0 blue: 0 alpha: .3]; // so I can see the bounds
    CGRect touchAreaFrame = self.bounds;
    CGFloat checkboxHitTargetExtension = 7;
    touchAreaFrame.origin.y -= checkboxHitTargetExtension;
    touchAreaFrame.size.height += (checkboxHitTargetExtension * 2);
    touchArea.frame = touchAreaFrame;
    [self addSubview: touchArea];

    // ... add listeners etc ...
  }
  return self;
}

Answer 1

You can use pointInside:withEvent: to define whether or not a specific point is "inside" the View. See the UIView reference for more info.

http://developer.apple.com/library/ios/#documentation/uikit/reference/UIView_Class/UIView/UIView.html

Also checkout CGRectOffset its very handy for making a CGRect bigger.

Answer 2

使按钮不是视图的子项，而是视图的兄弟，并且位于它的顶部，然后按钮的触摸没有剪切问题。