Marcin Swierczynski's blog

A few days ago, I had to implement a UIPickerView based select list with toolbar above it. The toolbar had to have a button to close the picker. The whole solution had to be very similar to the one used in a mobile version of Safari browser. How to do that?

The clue of the problem is contained in just two properties of UIResponder class: inputView and inputAccessoryView. The first one contains a view which will be displayed if its owner will become a first responder. For example, for UITextFields it’s a keyboard by default. The second one in turn, represents a view which will be displayed before (ie. above) the view pointed by inputView property.

So now it should be quite easy:

UIResponder *firstResponder; // use your future first responder

UIPickerView *pickerView = [[UIPickerView alloc] init];
pickerView.showsSelectionIndicator = YES;

firstResponder.inputView = pickerView;
[pickerView release];

UIToolbar *toolbar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, 320, 40)];
toolbar.barStyle = UIBarStyleBlackTranslucent;

firstResponder.inputAccessoryView = toolbar;
[toolbar release];

Unfortunately, it isn’t. Both inputView and inputAccessoryView are readonly properties, so we’ve to redeclare them in a subclass:

@property (readwrite, retain) UIView *inputView;
@property (readwrite, retain) UIView *inputAccessoryView;

What is the best, we aren’t limited to use this feature on UITextFields only. Because of fact that UIView inherits from UIResponder, we can attach this behaviour to all views, for example to a button or a table cell. To do that we have to override canBecomeFirstResponder method in our subclass. For example, the UIButton subclass implementation can look like this:

@implementation CustomButton //it's UIButton subclass

@synthesize inputView, inputAccessoryView;

- (BOOL) canBecomeFirstResponder {
    return YES;
}

- (void)dealloc {
	[inputView release];
	[inputAccessoryView release];
	[super dealloc];
}

@end