Question

I found this code online and am surprised that it basically does the opposite of what I want it to do. Here are the methods…

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view {
    UITableViewCell *cell = (UITableViewCell *)view;

    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
        [cell setBackgroundColor:[UIColor clearColor]];
        [cell setBounds: CGRectMake(0, 0, cell.frame.size.width -20 , 44)];
        cell.tag = row;
        UITapGestureRecognizer *singleTapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(toggleSelection:)];
        singleTapGestureRecognizer.numberOfTapsRequired = 1;
        [cell addGestureRecognizer:singleTapGestureRecognizer];
    }

    if ([selectedItems indexOfObject:[NSNumber numberWithInt:row]] != NSNotFound) {
        [cell setAccessoryType:UITableViewCellAccessoryCheckmark];
    } else {
        [cell setAccessoryType:UITableViewCellAccessoryNone];
    }
    cell.textLabel.text = @"Joe";

    return cell;
}

- (void)toggleSelection:(UITapGestureRecognizer *)recognizer {
    NSNumber *row = [NSNumber numberWithInt:recognizer.view.tag];
    NSUInteger index = [selectedItems indexOfObject:row];
    if (index != NSNotFound) {
        [selectedItems removeObjectAtIndex:index];
        [(UITableViewCell *)(recognizer.view) setAccessoryType:UITableViewCellAccessoryNone];
    } else {
        [selectedItems addObject:row];
        [(UITableViewCell *)(recognizer.view) setAccessoryType:UITableViewCellAccessoryCheckmark];
    }
}

The result is a simple checkmark by each UIPickerView item. This is great and all, but by default all of the elements of the PickerView are selected, which means they display a checkmark (I want none of them to be selected, except the ones I choose specifically in my code). Can you possible edit my methods and try to figure out how to do what I’m doing.

Also how am I going to be able to see the elements the user selected in my code. Help!

Answer 1

Judging from this block, there’s an array being stored called selectedItems, and it contains NSNumber objects corresponding to the rows.

if ([selectedItems indexOfObject:[NSNumber numberWithInt:row]] != NSNotFound) {
    [cell setAccessoryType:UITableViewCellAccessoryCheckmark];
} else {
    [cell setAccessoryType:UITableViewCellAccessoryNone];
}

If rowstarts checked, selectedItems must be initialised to contain an NSNumber object for every row. Try initialising it to be empty instead. To read what is selected, iterate through its content numbers.