如何在iPhone中检测UIPickerView的选择指示器上的触摸？

Question

I am working on UIPickerview control in iPhone app.I want to detect touch on selection indicator of UIPickerView.Please help me.Now i am using the following code

UITapGestureRecognizer *gestureRecognizer = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(pickerViewTapGestureRecognized:)];
 [self.picker addGestureRecognizer:gestureRecognizer];

-(void)pickerViewTapGestureRecognized:(UITapGestureRecognizer *)gestureRecognizer
{
CGPoint touchpoint = [gestureRecognizer locationInView:gestureRecognizer.view.superview];
CGRect frame = self.picker.frame;
CGRect selectorFrame = CGRectInset(frame, 0.0, self.picker.bounds.size.height * 0.85/2.0);
if (CGRectContainsPoint(selectorFrame, touchpoint)) {

  }
}

Answer 1

From here: Responding to touchesBegan in UIPickerView instead of UIView

Subclassing UIpickerView is the right way to do it. But you've to override the - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event method. This is the method called whenever you touch the screen and it returns the view that will react to the touch. In other words the view whose touchesBegan:withEvent: method will be called.

The UIPickerView has 9 subviews! In the UIPickerView class implementation - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event won't return self (this means the touchesBegan:withEvent: you write in the subclass won't be called) but will return a subview, exactly the view at index 4 (an undocumented subclass called UIPickerTable).

The trick is to make the - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event method to return self so you have control over the touchesBegan:withEvent:, touchesMoved:withEvent: and touchesEnded:withEvent: methods.