Overriding highlighted selection in UIPickerView

Question

I have a custom UIPickerView where I use:

-(UIView *)pickerView:(UIPickerView *)pickerView
       viewForRow:(NSInteger)row
     forComponent:(NSInteger)component 
      reusingView:(UIView *)view

to populate the picker with UILabels. Is there a way to disable the behavior of highlighting the selected row when touched?

I think this is a property of the underlying UITableViewCell inherent in the UIPickerView and I can't find a way to change it.

Answer 1

You need to make sure your custom view has the following properties:

1. It needs to be sized to the same dimensions that the UIPickerView expects based on your delegate methods -- pickerView:rowHeightForComponent: and pickerView:widthForComponent:. The default height is 44 if you're not specifying a custom height.
2. The background color must be [UIColor clearColor].
3. The view must capture all touches.

The one gotcha when using UILabel instances as the custom view is that UILabel defaults userInteractionEnabled to NO (UIView, on the other hand, defaults this property to YES).

Based on these requirements, the example code from Halle can be rewritten as follows. This example also correctly reuses previously created views, which is needed for fast scrolling performance.

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

  UILabel *pickerRowLabel = (UILabel *)view;
  if (pickerRowLabel == nil) {
    // Rule 1: width and height match what the picker view expects.
    //         Change as needed.
    CGRect frame = CGRectMake(0.0, 0.0, 320, 44);
    pickerRowLabel = [[[UILabel alloc] initWithFrame:frame] autorelease];
    // Rule 2: background color is clear. The view is positioned over
    //         the UIPickerView chrome.
    pickerRowLabel.backgroundColor = [UIColor clearColor];
    // Rule 3: view must capture all touches otherwise the cell will highlight,
    //         because the picker view uses a UITableView in its implementation.
    pickerRowLabel.userInteractionEnabled = YES;
  }
  pickerRowLabel.text = [pickerDataArray objectAtIndex:row];  

  return pickerRowLabel;
}

Answer 2

Setting the userInteractionEnabled property of UILabel to YES fixes the highlighting issue, but it also disables the UIPickerView from autoscrolling to select the row that has been touched.

If you want to disable the highlighting behavior, but maintain the UIPickerView's default autoscrolling functionality, call the setShowSelection function in the UITableCell instances contained in the UIPickerView. A way of doing this is to subclass the UILabel class similar to the following:

PickerViewLabel.h -

#import <UIKit/UIKit.h>

@interface PickerViewLabel:UILabel 
{
}

@end

PickerViewLabel.m -

#import "PickerViewLabel.h"

@implementation PickerViewLabel

- (void)didMoveToSuperview
{
 if ([[self superview] respondsToSelector:@selector(setShowSelection:)])
 {
  [[self superview] performSelector:@selector(setShowSelection:) withObject:NO];
 }
}

@end

Then, where you had previously been returning an instance of UILabel in pickerView:viewForRow:forComponent:reusingView:, return an instance of PickerViewLabel. As an example, using the code from Doug, you would replace all the cases of 'UILabel' with 'PickerViewLabel'. Just remember to remove the pickerRowLabel.userInteractionEnabled = YES; line.