iOS 11 - UINavigationItem titleView when using Large Titles mode

问题

I'm trying to understand either it's a bug or it's the expected behavior.

On iOS 10 and earlier we could set up a custom title, using navigationItem.titleView.
On iOS 11, when setting our navigationItem.largeTitleDisplayMode = .always and setting navigationItem.titleView = <Some cool UIButton> it's displaying both the normal navigation title bar and the large navigation title.

Illustration:

To sum up:

How can we use custom titleView on our Large Navigation Title?

EDIT : This is the expected result:

回答1:

I was able to replace the navigation bar big title with a custom view by using a subclass of UINavigationBar and manually changing the view hierarchy :

@interface MYNavigationBar : UINavigationBar

@end

@implementation MYNavigationBar

// ...

- (void)layoutIfNeeded
{
    [self setupTitle];
    [super layoutIfNeeded];
}

- (void)setupTitle
{
    // UINavigationBar
    // -> ...
    // -> _UINavigationBarLargeTitleView
    //   -> UILabel << Big Title Label
    //   -> UIView
    //     -> UILabel << Big Title Label animating from back button during transitions

    for (UIView *view in self.subviews) {
        NSString *className = NSStringFromClass(view.classForCoder);
        if ([className containsString:@"LargeTitleView"]) {
            for (UIView *view2 in view.subviews) {
                if ([view2 isKindOfClass:[UILabel class]]) {
                    [self convertLabel:(UILabel *)view2];
                }
                for (UIView *view3 in view2.subviews) {
                    if ([view3 isKindOfClass:[UILabel class]]) {
                        [self convertLabel:(UILabel *)view3];
                    }
                }
            }
        }
    }
}

- (void)convertLabel:(UILabel*)label
{
    // I kept the original label in the hierarchy (with the background color as text color)
    // and added my custom view as a subview. 
    // This allow the transformations applied to the original label to be also applied to mine.
}

Please note that Apple might reject your app because of this trick.

回答2:

I can't find any documentation on this, so I played a bit. It seems in iOS 11, you won't be able to get that title to be a button and display large at the left.

I don't know if this is a bug or the expected result, as it seems to be a new feature. The latest (iOS 11) Human Interface Guidelines (HIG) discuss the larger title label as being a way to give the user clear context. The HIG also discuss space between buttons. However, there's no discussion of using a button as the title.

To recreate, I set up a Single View project. I embedded the view controller in a navigation controller.

In ViewController.swift's viewDidLoad, I added this code:

    let titleButton = UIButton(type: .roundedRect)
    titleButton.setTitle("Hello Button!", for: UIControlState.normal)

    let navController = parent as! UINavigationController

    navController.navigationBar.topItem!.title = "Hello???"
    navController.navigationBar.topItem!.titleView = titleButton
    navController.navigationBar.prefersLargeTitles = true

This ends up looking something like your example.

IF I:

set .title to empty string, or remark the line out: navbar is stretched, and no title text shows (or title text set in Interface Builder shows)
remark out .prefersLargeTitles, or set it to false: the navbar is the normal height, the button displays, but no title text displays.
remark out the titleView line, AND:
- leave the .prefersLargeTitles set to true: the title text displays large at the left, and the navbar's height is stretched.
- set the .prefersLargeTitles to false: the title text displays in the top center, and the navbar is normal height.

Update: link to sample project on GitHub

来源：https://stackoverflow.com/questions/46437392/ios-11-uinavigationitem-titleview-when-using-large-titles-mode

标签

ios

navigationbar

ios11

uinavigationitem

titleview