Question

I would like to set up a global UITouch handler to debug all UITouch event that is going through the system and which view is the target, etc. How can I achieve this?

Answer 1

Make a subclass of UIApplication that overrides the sendEvent: method:

@interface MyApplication : UIApplication
@end

@implementation MyApplication

- (void)sendEvent:(UIEvent *)event {
    if (event.type == UIEventTypeTouches) {
        NSLog(@"Touch event: %@", event);
    }
    [super sendEvent:event];
}

@end

Pass the name of this subclass to UIApplicationMain in main.m:

#import <UIKit/UIKit.h>
#import "AppDelegate.h"
#import "MyApplication.h"

int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv,
            NSStringFromClass([MyApplication class]),
            NSStringFromClass([AppDelegate class]));
    }
}