Comments on: A UIPickerView with labels

By: JeffW

JeffW — Mon, 19 Jul 2010 19:26:46 +0000

I’m working on a iOS 4.0 app, when I try to use a LabledPickerView I get an EXE_BAD_ACCESS at this line:

if ([self.delegate respondsToSelector:@selector(pickerView:didSelectRow:inComponent:)])
[self.delegate pickerView:self didSelectRow:[self selectedRowInComponent:component] inComponent:component];

Has this code been broken by an Apple update, or am I doing something wrong?

Thanks!

By: Jeff

Jeff — Sat, 05 Sep 2009 03:02:55 +0000

This is great stuff!

I did notice, however, that its calling ‘didSelectRow’ upon creation (or at least when added to view). I haven’t narrowed it down exactly but has anyone else seen this?

By: Kare

Kare — Thu, 23 Jul 2009 23:27:54 +0000

You’re right. I fixed it so that method is no longer required. Well spotted.

By: Michael

Michael — Fri, 17 Jul 2009 05:52:25 +0000

Thanks for this useful little class! It’s strange that the iPhone HIG recommends doing exactly this, yet doesn’t suggest how to do it, nor do the APIs seem to support it easily!

By the way, I noticed that this class always tries to send a pickerView:didSelectRow:inComponent: message to its delegate, which crashes the app if the delegate doesn’t implement that method. The regular UIPickerView doesn’t do this, and indeed that method is listed as “optional” in the UIPickerViewDelegate protocol reference.

Otherwise, very nice work. Thanks again!

By: Kare

Kare — Fri, 05 Jun 2009 23:09:36 +0000

Cleaned up the code a bit, should have been done long time ago obviously. And removed some completely unnecessary reloading of views.

By: Kare

Kare — Wed, 22 Apr 2009 16:54:20 +0000

I finally got around to updating mySettings with Michael’s changes. Now just add something similar to this to your delegate and the labels will update automatically when a new row is selected:

// called when the wheel stops
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
        if (component == 0) {
                [(LabeledPickerView *)pickerView updateLabel:(row==1 ? @"min" : @"mins") forComponent:0];
        } else if (component == 1) {
                [(LabeledPickerView *)pickerView updateLabel:(row==1 ? @"sec" : @"secs") forComponent:1];
        }
}

The latest version can be found here: LabeledPickerView.h, LabeledPickerView.m.

By: Michael Kaye

Michael Kaye — Mon, 30 Mar 2009 22:33:23 +0000

sorry! In fact you only want to update the label if the label value has changed:

- (void) upDateLabel:(NSString *)labeltext forComponent:(NSUInteger)component {
UILabel *theLabel = (UILabel*)[self viewWithTag:component];

// Update label if it doesn’t match current label
if (theLabel.text != labeltext) {
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.75];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
theLabel.alpha = 0.00;
theLabel.text = labeltext;
theLabel.alpha = 1.00;
[UIView commitAnimations];
}

}

By: Michael Kaye

Michael Kaye — Mon, 30 Mar 2009 22:26:27 +0000

In fact Apple animates the label change so you could do this to replicate what apple does (not sure about the timings though!:

- (void) upDateLabel:(NSString *)labeltext forComponent:(NSUInteger)component {
UILabel *theLabel = (UILabel*)[self viewWithTag:component];

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.75];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
theLabel.alpha = 0.00;
theLabel.text = labeltext;
theLabel.alpha = 1.00;
[UIView commitAnimations];
}

By: Michael Kaye

Michael Kaye — Mon, 30 Mar 2009 22:18:01 +0000

Ok done…I needed to cast the viewWithTag to a UILabel of course,

I’m sure there is a better way to do this but for the moment using the component as the tag is the easiest way because nothing else in your code needs to be modified. Also it makes it very easy to find the label view regardless of where it is added.

So please go ahead and add this in.

Thanks again.

//add the following line

- (void)didMoveToWindow {
…
label.tag = component;
…
}

// Update method
- (void) upDateLabel:(NSString *)labeltext forComponent:(NSUInteger)component {
UILabel *theLabel = [self viewWithTag:component];
theLabel.text = labeltext;
//[theLabel setNeedsDisplay];
}

Obviously the best place to call the update method is in the pickerView didSelectRow method for the component being updated. i.e. [thePicker upDateLabel:NSLocalizedString(@"minute", @"") forComponent:1];

Thanks again for doing all the hard work.

Regards, Michael

By: Michael Kaye

Michael Kaye — Mon, 30 Mar 2009 22:09:15 +0000

Hi Kare,

Turns out it was a bug in another bit of code….so everything is working now (you don’t even need setNeedsDisplay).

I still have the warning though….which I’m trying to sort now. When I do I’ll come back to you.

Thanks, Michael.