[英]Why is viewWillDisappear called at the wrong time when using manual view containment?
这就是我使用包含API的方式。 根据文档是正确的。
[self.childViewController willMoveToParentViewController:nil];
[UIView animateWithDuration:0.25 animations:^{
self.childViewController.view.frame = ... // View Animation
} completion:^(BOOL finished) {
[self.childViewController.view removeFromSuperview]; // triggers `viewWillDisappear`
[self.childViewController removeFromParentViewController];
}];
我希望在动画开始之前viewDidDisappear
viewWillDisappear
,并在动画完成后viewDidDisappear
。 但是,在动画完成后,它们都会快速连续调用。
移动[self.childViewController.view removeFromSuperview];
到动画块修复了这个,但代码看起来错了:
[self.childViewController willMoveToParentViewController:nil];
[UIView animateWithDuration:0.25 animations:^{
self.childViewController.view.frame = ... // View Animation
[self.childViewController.view removeFromSuperview]; // triggers `viewWillDisappear`
} completion:^(BOOL finished) {
[self.childViewController removeFromParentViewController];
}];
有谁知道在正确的时间调用viewWillDisappear
的正确方法是什么?
答案是使用– beginAppearanceTransition:animated:
& endAppearanceTransition
如果要实现自定义容器控制器,请使用此方法告诉子项其视图将要显示或消失。 不要直接调用viewWillAppear:,viewWillDisappear:,viewDidAppear:或viewDidDisappear :.
更正后的代码:
[self.childViewController willMoveToParentViewController:nil];
[self.childViewController beginAppearanceTransition:NO animated:YES];
[UIView animateWithDuration:0.25 animations:^{
self.childViewController.view.frame = ...
} completion:^(BOOL finished) {
[self.childViewController.view removeFromSuperview];
[self.childViewController removeFromParentViewController];
[self.childViewController endAppearanceTransition];
}];
您没有通知childViewController已移动到parentViewController。
[yourViewController didMoveToParentViewController:self]
并在[self.childViewController willMoveToParentViewController:nil];
你没有提到谁将成为parentViewController。 指示添加childViewController的时间是一个很好的做法。 然后iOS应该知道何时触发viewWillDisappear
您正在通知viewController将移动到parentViewController,但如果您指明parentViewController是您的代码将按预期工作,则您不会指示whoViewController是谁。
当视图准备好离开parentView时,ViewWillDissappear将被触发。 这将在您的parentViewController或viewController的下一个willLayoutSubviews执行中发生,具体取决于viewControllers的层次结构
[UIView animateWithDuration:0.25 animations:^{
[self.childViewController.view removeFromSuperview];
self.childViewController.view.frame = ... // View Animation
[self.view addSubView:self.childViewController.view];
} completion:^(BOOL finished) {
[self.childViewController didMoveToParentViewController:self];
// triggers `viewWillDisappear`
[self.childViewController removeFromParentViewController];
}];
试试吧
这是一个Swift版本。 它将beginAppearanceTransition
置于动画关闭中,因此您可以获得类似UINavigationController
行为:您可以在子视图控制器的viewWillDisappear
调整可动画视图属性并自动获取动画。
let animator = UIViewPropertyAnimator(duration: 0.5, dampingRatio: 1) {
childViewController.willMove(toParentViewController: self)
childViewController.beginAppearanceTransition(false, animated: true)
childViewController.view.frame = ... // View Animation
}
animator.addCompletion { _ in
childViewController.view.removeFromSuperview()
childViewController.endAppearanceTransition()
childViewController.removeFromParentViewController()
}
animator.startAnimation()
注意endAppearanceTransition
必须被调用后view.removeFromSuperview
否则系统将发送重复的viewWillDisappear
viewDidDisappear
方法给您的孩子视图控制器。
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