touchesShouldBegin:(NSSet *)touches withEvent: inContentView: not get called

[wwzhdo]

inherited a class from UIScrollView, according to doc,
(BOOL)touchesShouldBeginNSSet *)touches withEventUIEvent *)event inContentViewUIView *)view should be called when user tap the screen, but it never happens, anything wrong with the code?

@interface Piano2View : UIScrollView {
}

@end

@implementation Piano2View

- (id)initWithFrame: (CGRect)frame {
if (self = [super initWithFrame:frame]) {
// Initialization code
}
return self;
}

//Overridden by subclasses to customize the default behavior when a finger touches down in displayed content.

- (BOOL)touchesShouldBegin: (NSSet *)touches withEvent: (UIEvent *)event inContentView: (UIView *)view
{
UITouch* touch = [[event touchesForView:self] anyObject];
CGPoint location = [touch locationInView:self];

return YES;

}