UIView will only animate once - ios

Question

I'm trying to animate an arrow spinning while my app downloads information. After each half spin, I want the app to check if the data has been downloaded yet. If not, the arrow should spin halfway again, with a short pause in between each spin.
-(void)animation {
[UIView animateWithDuration:0.7 delay:0 options:0 animations: ^{
imageView.transform = CGAffineTransformMakeRotation(180 * M_PI / 180);
} completion: ^(BOOL completed) {
if (completed && stillReloading) {
[self performSelector:#selector(animation) withObject:nil afterDelay:0.2];
}
}];
}
Even though the animation function is continually called, the image only rotates once. All calls made to the animation function after the first animation are ignored. Why is this? I don't want to set the repeat option on the animation as I do not know how many times the arrow will have the spin, and as I would like there to be a short pause between each spin.

Answer 1

This line
imageView.transform = CGAffineTransformMakeRotation(180 * M_PI / 180);
sets the angle to 180 degrees, and just that. The next time it's called same angle is used, so you see no animation.

Answer 2

If you want to rotate it again from its current position then you need to use a different method. CGAffineTransformMakeRotation makes a rotation from the identity transform. So what you end up with is this: Rotate to 180 degrees, rotate to 180 degrees, rotate to 180 degrees and the object never moves. Instead you need to use a method that applies the offset to the current transform. That is what the following method is for:
CGAffineTransformRotate(CGAffineTransform, CGFloat)
However, instead of applying it to CGAffineTransformIdentity as Saohooou's answer does, you should apply it to the current transform of your view.

Answer 3

Because you've made you view animate to angle (180 * M_PI / 180), it will never spring again if you set the same angle to it.
try this
CGFloat t = 180*M_PI / 180.0;
CGAffineTransform translateSpring = CGAffineTransformRotate(CGAffineTransformIdentity, t);
[UIView animateWithDuration:0.7 delay:0.0 options:nil animations:^{
imageView.transform = translateSpring;
} completion:^(BOOL completed) {
if (completed && stillReloading) {
//Use this method to let it spring back to its original angle
[UIView animateWithDuration:0.07 delay:0.0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
imageView.transform = CGAffineTransformIdentity;
} completion:NULL];
[self performSelector:#selector(animation) withObject:nil afterDelay:0.2];
}
}];
OR you can also set a dynamically update angle for your imageView to tranform into. See if it could help:)
Base on your problem, you can see my code, Here I use an animation to change the view back to its identity Transformation:
if (completed && stillReloading) {
//Use this method to let it spring back to its original angle
[UIView animateWithDuration:0.07 delay:0.0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
imageView.transform = CGAffineTransformIdentity;
} completion:NULL];
[self performSelector:#selector(animation) withObject:nil afterDelay:0.2];
}
// So if you want to transform it without getting seen, you can simply detele the animation code
if (completed && stillReloading) {
imageView.transform = CGAffineTransformIdentity;
[self performSelector:#selector(animation) withObject:nil afterDelay:0.2];
}

Answer 4

You will find that it is very difficult to get the arrow to rotate continuously clockwise in 180 degree increments. It will be simpler to rotate it in 90 degree increments.
You need to apply new rotation to the arrow's existing transform, to add more rotation each time.
-(void)animateArrowRotation {
[UIView animateWithDuration:0.35 delay:0 options:0 animations: ^{
imageView.transform = CGAffineTransformRotate(imageView.transform, M_PI_2);
} completion: ^(BOOL completed) {
if (completed && stillReloading) {
[self animateArrowRotation];
}
}];
}