iPhone - flipping views shows a white background

Question

I am using the flip animation to animate between two views in my viewcontroller. The problem is that the background shows a white blank background while the animation is tak

Answer 1

I think your issue might be that the UIWindow is shown during the animation. To fix this issue, set the background color of your main window. You can do this in code or in IB.

Answer 2

You begin by creating a fake main view, and set its background to black:

// Create the main view
    UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    contentView.backgroundColor = [UIColor blackColor];
    self.view = contentView;
    [contentView release]; 

Then, you create your front and back views, and add them to your main view:

// create front and back views
UIView *frontView = ...
UIView *backView = ...

If you are using IB, skip the previous step and add directly your views

// add the views
    [self.view addSubview:backView];
    [self.view addSubview:frontView];

Now do the flip animation as usual.

EDIT: Probably it does not work because in your code you are adding the frontView below the toolbar. Add first the backView, then the frontView and finally the toolbar using the addSubview: method. Then, use the following code to animate the flip:

- (IBAction) flipView{
    // Start Animation Block
    CGContextRef context = UIGraphicsGetCurrentContext();
    [UIView beginAnimations:nil context:context];
    [UIView setAnimationTransition: UIViewAnimationTransitionFlipFromLeft forView:self.view cache:YES];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    [UIView setAnimationDuration:1.0];

    // Animations
    [self.view exchangeSubviewAtIndex:0 withSubviewAtIndex:1];

    // Commit Animation Block
    [UIView commitAnimations];

}

Since the code performs [self.view exchangeSubviewAtIndex:0 withSubviewAtIndex:1]; the order in which you add the subviews is relevant.