display done button on UIPickerview

I have written the following code in the viewDidLoad method:

categoryPickerView=[[UIPickerView alloc]init];categoryPickerView.alpha = 0;[self.view addSubview:categoryPickerView];categoryPickerView.delegate=self;categoryPickerView.tag=1;

and called this method to hide picker view

- (IBAction)hidePickerView:(id)sender {    [UIView beginAnimations:nil context:nil];    [UIView setAnimationDuration:0.6];    CGAffineTransform transfrom = CGAffineTransformMakeTranslation(0, 200);    categoryPickerView.transform = transfrom;    categoryPickerView.alpha = categoryPickerView.alpha * (-1) + 1;    [UIView commitAnimations];}

My problem is that I want to display a "Done" button on a picker view and the picker view should hide on button click.