Start animate UIView before complete? - iphone

Question

I'm using [UIView animateWithDuration:...] for animate sequence of UIImageView views. Like this:
[UIView animateWithDuration:1.0 animations:^{
imageView.frame = newImageRectPosition;
}completion:^(BOOL finished){
//animate next UIImageView
}];
I need animate 'next UIImageView' not on completion. I need animate 'next UIImageView' on the middle of previous animation, not on completion. Is it possible to do so?

Answer 1

You can setup two UIView animation blocks, one which has a delay of half the duration of the first animation:
[UIView animateWithDuration:1.0
animations:^{ ... }
completion:^(BOOL finished){ ... }
];
[UIView animateWithDuration:1.0
delay:0.5
options:UIViewAnimationCurveLinear
animations:^{ ... }
completion:^(BOOL finished) { ... }
];

Answer 2

There are many options you can use to achieve the effect you're after. One which comes to mind is the use of timers.
Use an NSTimer with a firing interval half of that of your animation, and get the timer to fire off another animation. As long as the two animations don't interfere with each other, you should be ok.
An example would be as so:
NSTimer* timer;
// Modify to your uses if so required (i.e. repeating, more than 2 animations etc...)
timer = [NSTimer scheduledTimerWithTimeInterval:animationTime/2 target:self selector:#selector(runAnimation) userInfo:nil repeats:NO];
[UIView animateWithDuration:animationTime animations:^{
imageView.frame = newImageRectPosition;
} completion:nil];
- (void)runAnimation
{
// 2nd animation required
[UIView animateWithDuration:animationTime animations:^{
imageView.frame = newImageRectPosition;
} completion:nil];
}
With a timer, this could scale up if you needed to do more than two animations, and it all holds together if you need to change the animation time later on.