is there a uipickerview delegate method like scrollviewDidScroll?

Question

I have a customized UIPickerview and I do not want to use a datepicker. I want to implement the feature where when a user scrolls down/up the hours, the AM/PM component switches while the hour is scrolling. This means that I need to switch it before pickerView didSelectRow is called. Is there a way to do this?

Thanks

Answer 1

Use following method,

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
     // put your logic here.
}

Above method is from UIPickerViewDelegate, If user selects any element using pickerview, this method is automatically triggered.

Hope it helps to you.

Edit :

I think you should use following method for detecting - in which direction user is scrolling ?

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    NSLog(@"scrolling to row is %@",[NSString stringWithFormat:@"index_%i",row]);
    return [NSString stringWithFormat:@"index_%i",row];
}

whenever user is scrolling up/down above method is triggered automatically which is similar to UITableView. Remember UIPickerView is using UIPickerTableView which is private, so we can not detect the scrolling the way you want to have.

Let me explain the detecting the direction in pickerview.

Example. Visible rows are index_4,index_5,index_6,index_7. Now if user is scrolling down index_8 will be called. Similarly if user is scrolling to up index_3 will be called.

I hope this trick will solve your problem. Even-though let me know your feedback on this.

Answer 2

There is a trick to detect this but there is no delegate method/ property to detect if its scrolling or not

1. take a property as isScrolling
2. set isScrolling to true in func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? or equivalent method
3. set isScrolling to false in func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)

hope this helps, BTW this is what is explained in all the above mentioned answers

Answer 3

have to use this two UIPickerView delegate method for event:

DID END SCROLL:

- (void)pickerView:(UIPickerView *)pV didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    NSLog(@"pickerView didSelectRow %zd",row);
    // DID END SCROLL: CALL YOUR HEANDLER METHOD!!
}

WILL START SCROLLING:

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view{
    // WILL START SCROLLING: CALL YOUR HEANDLER METHOD!!
    UILabel* label = (UILabel*)view;
    if (!label){
        label = [UILabel new];
        [label setFrame:frame];
        [label setBackgroundColor:[UIColor clearColor]];
        [label setFont:[UIFont fontWithName:FONT_QUICKSAND_BOLD size:12]];
        [label setTextAlignment:NSTextAlignmentRight];
        [label setLineBreakMode:NSLineBreakByTruncatingMiddle];
        [label setTextColor:UIColorFromRGB(0X2692ff)];
        }
    //Update labeltext here
    [label setText:[NSString stringWithFormat:@"row %zd",row]];
    return label;
}

obviosly except for the building of UIPickerview (firstTIME!); so u have to implement a fake didendscroll event when you finish to build you piker or ignore first willstart scroll for the visible piker row