Add a 0.5 point height subview to UINavigationBar not show in iOS7

I have a class inherit from UINavigationBar and I want to add a separator line as its subview to separate the navigation bar and the navigation content.

The line's height is defined as following.

#define SEPERATOR_LINE_HEIGHT (1.0f / [UIScreen mainScreen].scale)

My code:

@interface MyPopNavigationBar : UINavigationBar

@end



@implementation MyPopNavigationBar {

    UIView *separatorLine;

}



- (id)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self) {

        self.clipsToBounds = YES;

        self.translucent = NO;



        separatorLine = [[UIView alloc] initWithFrame:CGRectMake(0, CGRectGetHeight(self.bounds) - SEPERATOR_LINE_HEIGHT, CGRectGetWidth(self.bounds), SEPERATOR_LINE_HEIGHT)];

        separatorLine.backgroundColor = [UIColor redColor];

        separatorLine.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin;

        [self addSubview:separatorLine];

    }

    return self;

}

This works well in both iOS 6 and iOS 8 (all Retina), but I can't see my separatorLine in iOS 7 (Retina, too)!

iOS 6 & 8:

iOS 7:

Besides, when I tried to set the separator line height to exact 1, it shows in all iOS versions.

separatorLine = [[UIView alloc] initWithFrame:CGRectMake(0, CGRectGetHeight(self.bounds) - 1, CGRectGetWidth(self.bounds), 1)];

What's wrong?

Answers

Solved this by myself. It's the autoresizingMask's fault 😂. I strongly suspect this a bug of iOS7.

I print the recursiveDescription in lldb, only to find the height of separatorLine is autoresized to zero in iOS7! In contrast, the value is 0.5 in iOS8.

So, remove this line:

separatorLine.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin;

And set the frame in layoutSubviews method of MyPopNavigationBar again to make it correct:

- (void)layoutSubviews {

    [super layoutSubviews];

    separatorLine.frame = CGRectMake(0, CGRectGetHeight(self.bounds) - SEPERATOR_LINE_HEIGHT, CGRectGetWidth(self.bounds), SEPERATOR_LINE_HEIGHT);

}

Then the line displays in all iOS versions.