iphone - Hiding/ Showing UIPickerView

Question

I Have an a touchesEnded event that checks for when a UITextField is pressed. What I would like it to do is is hide/show a UIPickerView. How can this be done?

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [[event allTouches] anyObject];
    if (CGRectContainsPoint([self.textField frame], [touch locationInView:self.view]))
    {
        NSString * error = @"Touched the TextField";
        UIAlertView * errorAlert = [[UIAlertView alloc] initWithTitle:@"Selection!" message:error delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [errorAlert show];
        //Want to show or hide UIPickerView
    }
}

I already have an allocated UIPickerView when touches occur

@interface ThirdViewController : UIViewController <UITextFieldDelegate,UIPickerViewDelegate> {
    IBOutlet UIPickerView *pickerView;
}

Answer 1

Toggling the "hidden" property will do the trick, but will also give a very abrupt reveal.

One way to avoid this is to get the picker to slide up from the bottom of the screen by embedding it inside a UIActionSheet.

Here's an example:

    UIActionSheet *sheet = [[UIActionSheet alloc] initWithTitle:nil 
delegate:nil cancelButtonTitle:nil destructiveButtonTitle:nil otherButtonTitles:nil];

    CGRect pickerFrame = CGRectMake(0, 0, 0, 0);
    UIPickerView *pickerView = [[UIPickerView alloc] initWithFrame:pickerFrame];
    pickerView.showsSelectionIndicator = YES;
    pickerView.dataSource = self;
    pickerView.delegate = self;
    [sheet addSubview:pickerView];
    [pickerView release];

    [sheet showInView:view];
    [sheet setBounds:CGRectMake(0, 0, 320, 415)];
    self.actionSheet = sheet; // assuming you have setup a property to hold the action sheet
    [sheet release];

When you've finished with the picker, dismiss it:

[self.actionSheet dismissWithClickedButtonIndex:0 animated:YES];

This approach can also be used to incorporate buttons in a bar above the picker ("Done", "Previous", "Next" etc) - there's a good explanation of how to do it here.