-[CustomWindow hitTest:withEvent:] implementation to forward events - iphone

Question

I have a custom window (that should be on top of everything, including the keyboard) to show an overlay thing, something like the overlay you see when pressing the volume up/down buttons in the device.
So I made a custom window OverlayWindow so far everything works fine and windows in the back are receiving their events normally. However hitTest:withEvent: is called several times and sometimes it even returns nil. I wonder if that is normal/correct? If not how can I fix that?
// A small (WIDTH_MAX:100) window in the center of the screen. If it matters
const CGSize screenSize = [[UIScreen mainScreen] bounds].size;
const CGRect rect = CGRectMake(((int)(screenSize.width - WIDTH_MAX)*0.5),
　　　　　　　((int)(screenSize.height - WIDTH_MAX)*0.5), WIDTH_MAX, WIDTH_MAX);
overlayWindow = [[CustomWindow alloc] initWithFrame:rect];
overlayWindow.windowLevel = UIWindowLevelStatusBar; //1000.0
overlayWindow.hidden = NO; // I don't need it to be the key (no makeKeyAndVisible)
　
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
// Find the front most window (with the highest window level) and
// call this method on that window. It should will make the event be
// forwarded to it
// Situation1: This method is called twice (or even more, it depend
// on the number of windows the app has) per event: Why? Is this the
// *normal* behaviour?
NSLog(#" ");
NSLog(#"Point: %# Event: %p\n", NSStringFromCGPoint(point), event);
UIView *view = nil;
if (CGRectContainsPoint(self.bounds, point)) {
NSLog(#"inside window\n");
NSArray *wins = [[UIApplication sharedApplication] windows];
__block UIWindow *frontMostWin = nil;
[wins enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLog(#"win: %#\n", obj);
if ([obj windowLevel] >= [frontMostWin windowLevel] && obj != self) {
frontMostWin = obj;
}
}];
NSLog(#"frontMostWindow:%#\n finding a new view ...\n", frontMostWin);
CGPoint p = [frontMostWindow convertPoint:point fromWindow:self];
view = [frontMostWindow hitTest:p withEvent:event];
// Situation2: sometimes view is nil here, Is that correct?
}
NSLog(#"resultView: %#\n", view);
return view;
}
EDIT:
Also I've noticed that
if hitTest:withEvent: always returns nil it works too. This is only when I call overlayWindow.hidden = NO;
if I call [overlayWindow makeKeyAndVisible] returning nil in hitTest:withEvent: does not always work. It looks like a key window requires a proper implementation of the hit testing method?
Am I missing something about event forwarding here?

Answer 1

Do frontMostWindow means frontMostWin?
It looks like even if we use only one UIWindow, hitTest:withEvent: will be executed on it at least 2 times. So, I guess it is normal.
You can receive null at
view = [frontMostWindow hitTest:p withEvent:event];
due to following reasons:
frontMostWindow is null itself (as example, if you have only one window)
p is ouside frontMostWindow bounds (as example, when frontMostWindow is keyboard and your touch is somewhere else)
frontMostWindow have property userInteractionEnabled set to NO;

Answer 2

hitTest:withEvent: being call several times is normal. This is probably because you only display a UILabel or UIImageView on the overlayed window and thus touches are automatically forwareded.
However I think you don't really need another OverlayWindow, instead you might consider a UIView on the top of the keyWindow. This should make your application cleaner...

Answer 3

I did face the same problem.
I tried to solve it based your post and another solution was found.
This code implemented in uiwindow overlaying on the top.
This code will pass events through the under window when area has no view.
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
NSLog(#" ");
NSLog(#"Point: %# Event: %p\n", NSStringFromCGPoint(point), event);
UIView *view = nil;
UIView *resultView = [super hitTest:point withEvent:event];
if (resultView == self) {
NSLog(#"touched in transparent window !!");
return nil;
}
NSLog(#"touched in view!!");
return resultView;
}
After all, Thanks. Your post is very helpful.