子UIPageViewController转全屏模态展示时视图尺寸为0不显示问题

• 子控制器移除流程不符合UIKit规范，生命周期方法调用顺序错误，导致外观转场回调失衡，出现Unbalanced calls to begin/end appearance transitions警告
• 提前手动调用didMoveToParentViewController:nil打乱了UIPageViewController的内部布局触发逻辑，其内部contentView无法获取正确的尺寸，最终frame变为0

1. 先在类扩展中声明保存原始布局上下文的属性 #

@interface MyPageViewController ()
@property (nonatomic, weak) UIViewController *originalParentViewController;
@property (nonatomic, weak) UIView *originalSuperview;
@property (nonatomic, assign) CGRect originalFrame;
// 使用AutoLayout布局可额外声明保存原约束
// @property (nonatomic, copy) NSArray *originalConstraints;
@end

2. 修正点击手势的处理逻辑 #

严格遵循UIKit子控制器的移除规范，同时给视图添加初始尺寸避免布局失效：

- (void)handleTapGesture {
    // 保存原始状态，用于dismiss后恢复
    self.originalParentViewController = self.parentViewController;
    self.originalSuperview = self.view.superview;
    self.originalFrame = self.view.frame;

    // 标准子控制器移除流程：先调用willMove，再移除视图，最后移除父控制器关联
    [self willMoveToParentViewController:nil];
    [self.view removeFromSuperview];
    [self removeFromParentViewController];
    // removeFromParentViewController会自动触发didMoveToParentViewController:nil，无需手动调用

    // 给视图设置初始全屏frame，适配模态转场的布局上下文
    self.view.frame = [UIScreen mainScreen].bounds;
    self.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

    self.modalPresentationStyle = UIModalPresentationFullScreen;
    [self.originalParentViewController presentViewController:self animated:YES completion:nil];
}

3. 补充dismiss后恢复原位置的逻辑 #

- (void)handleFullScreenDismiss {
    [self dismissViewControllerAnimated:YES completion:^{
        // 按标准流程将控制器插回原父层级
        [self.originalParentViewController addChildViewController:self];
        self.view.frame = self.originalFrame;
        [self.originalSuperview addSubview:self.view];
        [self didMoveToParentViewController:self.originalParentViewController];

        // 清空临时保存的状态
        self.originalParentViewController = nil;
        self.originalSuperview = nil;
    }];
}

内容的提问来源于stack exchange，提问作者ashipma