title: How to Show and Hide UIPickerView like iOS Keyboard?
body: <p>I have this code to hide UIPickerView by default:</p>
  
  <pre><code>- (void)viewDidLoad
  {
      [super viewDidLoad];
      [_memberList setAlpha:0];
  }
  </code></pre>
  
  <p>and this code to show UIPickerView when a button tapped :</p>
  
  <pre><code>- (IBAction)buttonChooseMember {    
      [UIView animateWithDuration:0.6 delay:0. options:UIViewAnimationOptionCurveEaseInOut animations:^{
          [_memberList setAlpha:1];
      } completion:nil];
  }
  </code></pre>
  
  <p>and the last thing is this, to hide keyboard when user tap anywhere :</p>
  
  <pre><code>- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
      for (UIView * txt in self.view.subviews){
          if ([txt isKindOfClass:[UITextField class]]) {
              [txt resignFirstResponder];
          }else if ([txt isKindOfClass:[UIPickerView class]]) {
              [UIView animateWithDuration:0.6 delay:0. options:UIViewAnimationOptionCurveEaseInOut animations:^{
                  [_registerMLMList setAlpha:0];
              } completion:nil];
          }
      }
  }
  </code></pre>
  
  <p>but all of this just give me 'appear' animation, because it's only changing Alpha value from 0 to 1 (and vice versa). not slide-up or slide-down just like iOS keyboard.</p>
  
  <p>I tried to use this animation below to have iOS keyboard look and feel on my UIPickerView :</p>
  
  <pre><code>- (IBAction)hidePicker {
  
      UIPickerView *pickerView = [[UIPickerView alloc] init]; // default frame is set
      float pvHeight = pickerView.frame.size.height;
      float y = _screen.bounds.size.height - (pvHeight * -2); // the root view of view controller
      [UIView animateWithDuration:0.5f delay:0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
          self.picker.frame = CGRectMake(0 , y, pickerView.frame.size.width, pvHeight);
      } completion:nil];
  }
  
  - (IBAction)showPicker {
      UIPickerView *pickerView = [[UIPickerView alloc] init]; // default frame is set
      float pvHeight = pickerView.frame.size.height;
      float y = _screen.bounds.size.height - (pvHeight); // the root view of view controller
      [UIView animateWithDuration:0.5f delay:0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
          self.picker.frame = CGRectMake(0 , y, pickerView.frame.size.width, pvHeight);
      } completion:nil];
  }
  </code></pre>
  
  <p>I like this animation, it looks like iOS keyboard animation, but the problem with this animation is... when my app is loaded, the UIPickerView is already shows up. how to hide it when it loads up for the first time?</p>
  
  <p>thank you.</p>