带有扩展导航栏的iOS过渡

Question

我正在为我的应用程序使用扩展的导航栏，将其高度增加了30点。 为此，我将UINavigationBar子类化，这是我的CustomNavigationBar.m：

CGFloat CustomNavigationBarHeightIncrease = 30.f;

@implementation CustomNavigationBar

- (CGSize)sizeThatFits:(CGSize)size {

  CGSize amendedSize = [super sizeThatFits:size];
  amendedSize.height += CustomNavigationBarHeightIncrease;

  return amendedSize;
}

- (id)initWithCoder:(NSCoder *)aDecoder {

  self = [super initWithCoder:aDecoder];

  if (self) {
    [self initialize];
  }

  return self;
}

- (id)initWithFrame:(CGRect)frame {

  self = [super initWithFrame:frame];

  if (self) {
      [self initialize];
  }

  return self;
}

- (void)initialize {

  [self setTransform:CGAffineTransformMakeTranslation(0, -(CustomNavigationBarHeightIncrease))];
}

- (void)layoutSubviews {
  [super layoutSubviews];

  NSArray *classNamesToReposition = @[@"_UINavigationBarBackground"];

  for (UIView *view in [self subviews]) {

      if ([classNamesToReposition containsObject:NSStringFromClass([view class])]) {

          CGRect bounds = [self bounds];
          CGRect frame = [view frame];
          frame.origin.y = bounds.origin.y + CustomNavigationBarHeightIncrease - 20.f;
          frame.size.height = bounds.size.height + 20.f;

          [view setFrame:frame];
      }
  }
}

@end

然后，在视图控制器的viewDidLoad中，设置导航项的titleView属性，如下所示：

self.navigationItem.title = @"";
UIImage* logoImage = [UIImage imageNamed:@"welcome"];
self.navigationItem.titleView = [[UIImageView alloc] initWithImage:logoImage];
self.navigationItem.titleView.contentMode = UIViewContentModeScaleAspectFill;
self.navigationItem.titleView.contentMode = UIViewContentModeBottom;

我的titleView框架的高度为80点。

到那时为止，一切正常，但是当我更改视图控制器时（在所使用的图像在视图控制器之间更改时）出现问题。 动画一开始，我的图像底部（以及titleView中的图像，而不是整个导航栏）就被我的额外高度裁剪了，过渡正确地进行了（嗯，只剩下了一点），并且完成后，将出现新图像的裁剪部分。

我希望很清楚，似乎我无法在添加的导航栏上看到任何动画。

感谢您的帮助，我真的不知道从哪里开始。

Answer 1

与其对UINavigationBar进行子类化，不如尝试对其进行自定义。 它将需要您在Interface Builder中设置约束以抵消Navigation Bar的大小，但这并不困难：

#pragma mark - Navigation Bar Setup

- (void)setupNavBar
{
    [self.navigationController setNavigationBarHidden:NO animated:YES];

    self.navigationController.navigationBar.barStyle = UIBarStyleBlackTranslucent;
    self.navigationController.navigationBar.barTintColor = [UIColor blackColor];

    [self.navigationController.navigationBar setBounds:CGRectMake(0, 0, self.view.frame.size.width, 80)];

// Customizing the back button in the Nav Bar

    self.navigationItem.hidesBackButton = YES;

    UIButton *backButton = [UIButton buttonWithType:UIButtonTypeCustom];
    backButton.frame = CGRectMake(0, 0, 30, 30);
    [backButton setImage:[UIImage imageNamed:@"backbtn"] forState:UIControlStateNormal];
    [backButton addTarget:self action:@selector(backButtonPressed) forControlEvents:UIControlEventTouchUpInside];

    UIBarButtonItem *leftButton = [[UIBarButtonItem alloc] initWithCustomView:backButton];
    self.navigationItem.leftBarButtonItem = leftButton;

    UIImage *title = [UIImage imageNamed:@"title_image"];
    UIImageView *titleImgView = [[UIImageView alloc] initWithImage:title];
    titleImgView.frame = CGRectMake(10, 15, 85, 24);

    UIView *titleView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 105, 50)];
    [titleView addSubview:titleImgView];

    self.navigationItem.titleView = titleView;
}

调用后退按钮的示例方法：

- (void)backButtonPressed
{
    for (UIViewController *vc in self.childViewControllers)
    {
        if ([vc isEqual:[PinningVC class]])
        {
            [vc removeFromParentViewController];
        }
    }

    [self.navigationController popViewControllerAnimated:NO];
}