We don’t add UIPickerView as subview. There is a trick to achieve this.

Create a dummy UITextField

This text field is not visible to user, is a hidden field

ViewController.m

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#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) UITextField *pickerViewTextField;
@end
@implementation ViewController
@synthesize pickerViewTextField = _pickerViewTextField;
- (void)viewDidLoad
{
[super viewDidLoad];
// set the frame to zero
self.pickerViewTextField = [[UITextField alloc] initWithFrame:CGRectZero];
[self.view addSubview:self.pickerViewTextField];
UIPickerView *pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 0, 0)];
pickerView.showsSelectionIndicator = YES;
pickerView.dataSource = self;
pickerView.delegate = self;
// set change the inputView (default is keyboard) to UIPickerView
self.pickerViewTextField.inputView = pickerView;
// add a toolbar with Cancel & Done button
UIToolbar *toolBar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
toolBar.barStyle = UIBarStyleBlackOpaque;
UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(doneTouched:)];
UIBarButtonItem *cancelButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(cancelTouched:)];
// the middle button is to make the Done button align to right
[toolBar setItems:[NSArray arrayWithObjects:cancelButton, [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil], doneButton, nil]];
self.pickerViewTextField.inputAccessoryView = toolBar;
...
}

Trigger the picker view when click on UIButton

ViewController.m

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...
- (IBAction)someButtonTouched:(UIButton *)sender
{
[self.pickerViewTextField becomeFirstResponder];
}

Add methods for bar buttons

ViewController.m

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- (void)cancelTouched:(UIBarButtonItem *)sender
{
// hide the picker view
[self.pickerViewTextField resignFirstResponder];
}
- (void)doneTouched:(UIBarButtonItem *)sender
{
// hide the picker view
[self.pickerViewTextField resignFirstResponder];
// perform some action
}

Add dataSource & delegate for UIPickerView

ViewController.m

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#pragma mark - UIPickerViewDataSource
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
return [yourItems count];
}
#pragma mark - UIPickerViewDelegate
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
NSString *item = [yourItems objectAtIndex:row];
return item;
}
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
// perform some action
}

Don’t forget to make your ViewController conform to the protocols

ViewController.h

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@interface ViewController : UIViewController <UIPickerViewDataSource, UIPickerViewDelegate>

You’re done :)