Closing a UIpicker in an iphone app - objective-c

Question

I'm new to the iphone dev. The app I'm making uses the picker to input value from the user. I have managed to make the picker hidden until the user hits the button. I used the mypicker.alpha = 0; in viewdidload so the the picker is invisible when the program starts. When the user hits the start button it executes the code mypicker.alpha=1;. I want the picker to close after the user chooses a value. How do I do that? anyone have any hints or tutorials ? I looked at few but they were confusing! Also how do I make the picker appear from the bottom up ? (like the keyboard !)

Answer 1

One method I recently started using is to put a shade button behind the picker, a large transparent black button the size of the screen, color black with alpha=0.3 ([UIColor colorWithWhite:0 alpha:0.3f] I think it was). This just puts a transparent "shade" over the rest of the screen except for the picker, similar to how it looks when you use UIAlertView. Then hook up the button so that it sends resignFirstResponder to the picker. Now when the user is done picking, they just tap anywhere outside the picker in the shaded area, and the button resigns the picker, and the picker can be slid down and the button faded out with an animation.
The picker slide up/down animation can be done and I have the code for it at home but don't have access to it right now. You can make it appear just like the keyboard and send the same notifications that the keyboard sends.

Answer 2

Don't use:
mypicker.alpha = 1;
mypicker.alpha = 0;
You should use:
mypicker.hidden = YES;
mypicker.hidden = NO;
in order to show or hide the picker.
In order to make it appear from the bottom, you can use block animations. I would use:
The .h file:
#interface viewController : UIViewController <UIPickerViewDelegate, UIPickerViewDataSource> {
BOOL shouldMoveDown;
IBOutlet UIPickerView * picker;
}
- (IBAction)movePicker;
The .m file:
#pragma mark - View lifecycle
- (void)viewDidLoad; {
[super viewDidLoad];
picker.hidden = YES;
shouldMoveDown = NO;
picker.userInteractionEnabled = NO;
}
- (IBAction)movePicker; {
if(shouldMoveDown){
[UIView animateWithDuration:1.0
animations:^{
CGRect newRect = picker.frame;
newRect.origin.y += 236; // 480 - 244 (Height of Picker) = 236
picker.frame = newRect;
}
completion:^(BOOL finished){
[UIView animateWithDuration:1.0
animations:^{
picker.hidden = YES;
shouldMoveDown = NO;
picker.userInteractionEnabled = NO;
}
completion:^(BOOL finished){
;
}];
}];
}
else{
picker.hidden = NO;
//picker.frame = CGRectMake(picker.frame.origin.x, 480, picker.frame.size.width, picker.frame.size.height);
[UIView animateWithDuration:1.0
animations:^{
CGRect newRect = picker.frame;
newRect.origin.y -= 236; // 480 - 244 (Height of Picker) = 236
picker.frame = newRect;
}
completion:^(BOOL finished){
[UIView animateWithDuration:1.0
animations:^{
shouldMoveDown = YES;
picker.userInteractionEnabled = YES;
}
completion:^(BOOL finished){
;
}];
}];
}
}
#pragma mark -
#pragma mark Picker Delegate Methods
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)thePickerView; {
return 1;
}
- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component; {
return 1;
}
- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component; {
return #"1";
}
- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component; {
}
Obviously you can set the picker up any way you would like to. You can also alter the speed at which this happens too! Hope this helps!