ios - 查看将消失 : Determine whether view controller is being popped or is showing a sub-view controller

Question

我正在努力寻找解决此问题的好方法。在 View Controller 的 -viewWillDisappear: 方法中，我需要找到一种方法来确定是因为 View Controller 被推到导航 Controller 的堆栈上，还是因为 View Controller 正在消失因为它已被弹出。

目前我正在设置诸如 isShowingChildViewController 之类的标志，但它变得相当复杂。我认为我可以检测到它的唯一方法是在 -dealloc 方法中。

Answer 1

您可以使用以下内容。

- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];
  NSArray *viewControllers = self.navigationController.viewControllers;
  if (viewControllers.count > 1 && [viewControllers objectAtIndex:viewControllers.count-2] == self) {
    // View is disappearing because a new view controller was pushed onto the stack
    NSLog(@"New view controller was pushed");
  } else if ([viewControllers indexOfObject:self] == NSNotFound) {
    // View is disappearing because it was popped from the stack
    NSLog(@"View controller was popped");
  }
}

当然，这是可能的，因为 UINavigationController 的 View Controller 堆栈(通过 viewControllers 属性公开)在调用 viewWillDisappear 时已经更新。