我正在编写一个自定义UIStoryboardSegue，它会在perform方法的两个视图控制器（源和目标）中触发动画。以下是：
- (void)perform
{
UIViewController * sourceViewController = [self sourceViewController];
UIViewController * destinationViewController = [self destinationViewController];
//
UIView * sourceView = sourceViewController.view;
UIView * destinationView = destinationViewController.view;
[sourceView addSubview:destinationView];
id <HyTransition> presentingTransition = [self presentingTransitionForViewController:destinationViewController];
id <HyTransition> dismissingTransition = [self dismissingTransitionForViewController:sourceViewController];
[presentingTransition performWithTransitionContext:self.presentingContext];
[dismissingTransition performWithTransitionContext:self.dismissingContext];
}
每个视图控制器都返回一个id <HyTransition>类型的对象，该对象负责制作动画。在这种情况下，我返回HyTransitionWithCallback，这是一个子类。然后我动画一些约束：
- (id <HyTransition>)presentingTransition
{
__weak HyPresentationViewController * weakSelf = self;
return [HyTransitionWithCallback transitionWithCallback:^(__weak HyTransitionContext * context) {
[weakSelf.pageControlBottomConstraint setConstant:-weakSelf.view.frame.size.height];
[weakSelf.loginButtonBottomConstraint setConstant:-weakSelf.view.frame.size.height];
[weakSelf.view layoutIfNeeded];
[UIView animateWithDuration:0.4f
delay:1.0f
usingSpringWithDamping:1.0f
initialSpringVelocity:0.0f
options:UIViewAnimationOptionCurveEaseIn
animations:^{
[weakSelf.pageControlBottomConstraint setConstant:56.0f];
[weakSelf.loginButtonBottomConstraint setConstant:8.0f];
[weakSelf.view layoutIfNeeded];
}
completion:^ (BOOL finished) {
if (finished) {
[context setTransitionFinished:YES];
}
}];
}];
}
正在调用此方法，但动画根本没有运行。我甚至尝试将延迟设置为10.0f，但立即调用completion块（finished设置为YES），当视图显示时，约束位于其最终位置（56.0f和8.0f）。
我的第一个猜测是动画过早触发，但我不能在perform方法中为目标视图设置动画效果吗？似乎这个方法在viewWillAppear之前被调用，这就是为什么我说它可能过早被调用。
编辑：在动画之前，viewWillAppear:不仅被称为，而且viewDidAppear:也是如此。我想这个动画毕竟不会被触发，但这也意味着我不知道动画为什么不运行。
编辑：好的，所以我让动画工作，但不是我想要的那个。此代码有效：
- (id <HyTransition>)presentingTransition
{
__weak HyPresentationViewController * weakSelf = self;
return [HyTransitionWithCallback transitionWithCallback:^(__weak HyTransitionContext * context) {
[weakSelf.pageControlBottomConstraint setConstant:100.0f];
[weakSelf.loginButtonBottomConstraint setConstant:100.0f];
[weakSelf.view setNeedsUpdateConstraints];
[UIView animateWithDuration:5.4f
animations:^ {
[weakSelf.view layoutIfNeeded];
}
completion:^ (BOOL finished) {
if (finished) {
[context setTransitionFinished:YES];
}
}];
}];
}
这激发了他们自然位置的约束，但我想要完全相反。也就是说，首先我想错放约束，然后将它们动画到它们的位置。这就是我所拥有的：
- (id <HyTransition>)presentingTransition
{
__weak HyPresentationViewController * weakSelf = self;
return [HyTransitionWithCallback transitionWithCallback:^(__weak HyTransitionContext * context) {
[weakSelf.pageControlBottomConstraint setConstant:100.0f];
[weakSelf.loginButtonBottomConstraint setConstant:100.0f];
[weakSelf.view setNeedsUpdateConstraints];
[weakSelf.view layoutIfNeeded];
[weakSelf.pageControlBottomConstraint setConstant:56.0f];
[weakSelf.loginButtonBottomConstraint setConstant:8.0f];
[weakSelf.view setNeedsUpdateConstraints];
[UIView animateWithDuration:5.4f
animations:^ {
[weakSelf.view layoutIfNeeded];
}
completion:^ (BOOL finished) {
if (finished) {
[context setTransitionFinished:YES];
}
}];
}];
}
这不起作用;它没有再动画。
编辑：这很奇怪......请使用以下代码：
- (id <HyTransition>)presentingTransition
{
__weak HyPresentationViewController * weakSelf = self;
return [HyTransitionWithCallback transitionWithCallback:^(__weak HyTransitionContext * context) {
[weakSelf.pageControlBottomConstraint setConstant:100.0f];
[weakSelf.loginButtonBottomConstraint setConstant:100.0f];
[weakSelf.view setNeedsUpdateConstraints];
[weakSelf.view updateConstraints];
[weakSelf.pageControlBottomConstraint setConstant:56.0f];
[weakSelf.loginButtonBottomConstraint setConstant:8.0f];
[weakSelf.view setNeedsUpdateConstraints];
[UIView animateWithDuration:5.4f
animations:^ {
[weakSelf.view layoutIfNeeded];
}
completion:^ (BOOL finished) {
if (finished) {
[context setTransitionFinished:YES];
}
}];
}];
}
动画运行，但根本不是我所期待的。页面控件什么都不做，按钮动画字体大小！按钮的文字从非常小到标准尺寸...这必须是伏都教xD