How can I click a button behind a transparent UIView?

Asked 2010-06-15T15:51:41.153

203

Let's say we have a view controller with one sub view. the subview takes up the center of the screen with 100 px margins on all sides. We then add a bunch of little stuff to click on inside that subview. We are only using the subview to take advantage of the new frame ( x=0, y=0 inside the subview is actually 100,100 in the parent view).

Then, imagine that we have something behind the subview, like a menu. I want the user to be able to select any of the "little stuff" in the subview, but if there is nothing there, I want touches to pass through it (since the background is clear anyway) to the buttons behind it.

How can I do this? It looks like touchesBegan goes through, but buttons don't work.

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2 Answers

As far as I know, you are supposed to be able to do this by overriding the hitTest: method. I did try it but could not get it to work properly.

In the end I created a series of transparent views around the touchable object so that they did not cover it. Bit of a hack for my issue this worked fine.

answered 2010-06-15T16:10:08.030

I created a category to do this.

a little method swizzling and the view is golden.

The header

//UIView+PassthroughParent.h
@interface UIView (PassthroughParent)

- (BOOL) passthroughParent;
- (void) setPassthroughParent:(BOOL) passthroughParent;

@end

The implementation file

#import "UIView+PassthroughParent.h"

@implementation UIView (PassthroughParent)

+ (void)load{
    Swizz([UIView class], @selector(pointInside:withEvent:), @selector(passthroughPointInside:withEvent:));
}

- (BOOL)passthroughParent{
    NSNumber *passthrough = [self propertyValueForKey:@"passthroughParent"];
    if (passthrough) return passthrough.boolValue;
    return NO;
}
- (void)setPassthroughParent:(BOOL)passthroughParent{
    [self setPropertyValue:[NSNumber numberWithBool:passthroughParent] forKey:@"passthroughParent"];
}

- (BOOL)passthroughPointInside:(CGPoint)point withEvent:(UIEvent *)event{
    // Allow buttons to receive press events.  All other views will get ignored
    if (self.passthroughParent){
        if (self.alpha != 0 && !self.isHidden){
            for( id foundView in self.subviews )
            {
                if ([foundView alpha] != 0 && ![foundView isHidden] && [foundView pointInside:[self convertPoint:point toView:foundView] withEvent:event])
                    return YES;
            }
        }
        return NO;
    }
    else {
        return [self passthroughPointInside:point withEvent:event];// Swizzled
    }
}

@end

You will need to add my Swizz.h and Swizz.m

located Here

After that, you just Import the UIView+PassthroughParent.h in your {Project}-Prefix.pch file, and every view will have this ability.

every view will take points, but none of the blank space will.

I also recommend using a clear background.

myView.pas


                        
                        
                            answered 2012-06-20T03:03:22.537



        
        
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