Proper way to hide status bar on iOS, with animation and resizing root view

Question

Consider a view controller that needs to slide out (or hide) the status bar when a button is clicked.

- (void) buttonClick:(id)sender
{
    [[UIApplication sharedApplication] setStatusBarHidden:YES
                                            withAnimation:UIStatusBarAnimationSlide];
}

The above effectively hides the status bar, but does not resize the root view appropriately, leaving a 20 pixel gap on top.

What I expected is the root view to expand over the space that was previously used by the status bar (animated, with the same duration than the status bar animation).

What's the proper way of doing this?

(I'm aware there are plenty of similar questions, but I couldn't find any about hiding the status bar on demand as opposed to hiding it to display a new view controller)

The "brute force" approach

Obviously, the following works...

[[UIApplication sharedApplication] setStatusBarHidden:YES
                                        withAnimation:UIStatusBarAnimationSlide];
[UIView animateWithDuration:0.25 animations:^{
    CGRect frame = self.view.frame;
    frame.origin.y -= 20;
    frame.size.height += 20;
    self.view.frame = frame;
}];

...but has disadvantages:

• Hardcodes the duration of the slide animation
• Hardcodes the height of the status bar
• The root view origin stays at (0,-20). I like my frames to start at (0,0) whenever possible.

What I already tried

• Made sure the autoresize mask of the root view has UIViewAutoresizingFlexibleTopMargin and UIViewAutoresizingFlexibleHeight.
• Called [self.view setNeedsLayout] after hiding the status bar.
• Called [self.view setNeedsDisplay] after hiding the status bar.
• Set wantsFullScreenLayout to YES before and after hiding the status bar.

Answer 1

This works fine and has nothing hard coded.

CGRect appFrame = [[UIScreen mainScreen] applicationFrame];

[[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation:UIStatusBarAnimationSlide];
[UIView animateWithDuration:0.25 animations:^{
    self.navigationController.navigationBar.frame = self.navigationController.navigationBar.bounds;
    self.view.window.frame = CGRectMake(0, 0, appFrame.size.width, appFrame.size.height);
}];