How to animate a button change in UINavigationBar?

Question

I am calling the -(void)setEditing:(BOOL)editing animated:(BOOL)animated method in my code to swap between two buttons on the RHS of my navigation bar.

-(void)setEditing:(BOOL)editing animated:(BOOL)animated {  
  [super setEditing:editing animated:animated];  

  // Toggle ‘+’ and ‘Add To Order’ button.    

  if( editing ) {
    self.navigationItem.rightBarButtonItem = self.addItemButton;  
  }  
  else {           
    self.navigationItem.rightBarButtonItem = self.addToOrderButton;  
  } 
}

Where self.addItemButton and self.addToOrderButton are ivars containing predefined UIBarButtonItems, setup in awakefromNib.

The button in self.addToOrderButton is significantly wider then the one in self.addItemButton, so I’d like their to be a subtle animation between the two widths when the change in editing state is triggered (by tapping a standard editButtonItem on the LHS of the navigation.

If I surround the whole if:else with [UIView beginAnimations:nil context:NULL]; and [UIView commitAnimations]; the button change does animate, but with their positions—flying into place individually from the top left—rather than in place and just animating their widths.

How I animate the navigation bar elements so that each individual one (the RHS button, the title) animate in more appropriate, restrained ways?

lxt · Accepted Answer · 2011-02-15 17:05:57Z

78

self.navigationItem.rightBarButtonItem = self.addToOrderButton;

There are specific methods you can use to animate the right and left bar button items:

 [self.navigationItem setRightBarButtonItem: self.addToOrderButton animated:YES];

...which will animate it for you. If you need everything to animate (including the title) you can also use the setItems:animated: method of your navigation bar (pass it in an array of the navigation items you'd like to display)

answered Feb 15, 2011 at 17:05

lxt

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7 Comments

creednmd Over a year ago

I’ve accepted the answer, as that does exactly what you describe and works okay. Many thanks. As an aside, is there a method to tweak the actual animation that's occurring? As presented here, that does a cross-fade—which is fine—but a combination of cross-fade for the text and animated move of the button LHS for the ‘frame’ would be even better.

lxt Over a year ago

There's no direct method in the SDK, no. You could probably implement something yourself, but it would be non-trivial (something like overriding the method with a category and replacing it with your own transition).

creednmd Over a year ago

Sounds like something that I would need to study the docs on; thanks for getting me on the right track though.

richy Over a year ago

also if you don't know you can use: [self.navigationItem setLeftBarButtonItem:nil animated:YES]; this can be used in combination with: [self.navigationItem setHidesBackButton:NO animated:YES];

Andrii Chernenko Over a year ago

Before you try to use setItems:animated:, be aware that it cannot be used on the navigationController's navigationBar. You'll get slapped with the following exception: Cannot call setItems:animated: directly on a UINavigationBar managed by a controller.

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