单行UILabel拥抱不适用于自动收缩

Question

I've a UILabel with the following properties:

• A very big font
• Fixed left margin to superview
• Fixed right margin to superview
• Centered vertically
• Autoshrinks to a minimum font size to avoid truncating the text as much as possible.
• Single line
• Vertical hugging priority set to Required (1000)

The problem I'm having is that the label doesn't vertically hug the text , as you can see in the image bellow there's a lot of space on top and bellow the text.

I uploaded the sample project here .

Thanks!

Answer 1

试试下面的代码：

[self.myLabel setAutoresizingMask:UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleWidth]; 

Answer 2

I was able to achieve the desired effect with a workaround. It's not the perfect solution and doesn't work on all cases but it did solve my issue at least.

SUMMARY

The workaround works as follows:

1. Find the actual font (the font that is being actually used by the label).
2. Calculate the text height with the actual font.
3. Use UIViews 's - (UIEdgeInsets)alignmentRectInsets ( reference ) to modify alignment rect that is used by Autolayout to position views based on the actual text height.

With all this, I was able to go from this:

to this:

PROBLEMS

• Need to set baseline to center
• Only implemented for exceeding height (doesn't work for right and left margins)
• Only for single line labels

CODE

Declared a UILabel subclass as follows

@implementation HuggingLabel

- (UIEdgeInsets)alignmentRectInsets
{
    if (self.numberOfLines != 1)
    {
        if ([super respondsToSelector:@selector(alignmentRectInsets)])
            return [super alignmentRectInsets];
        else
            return UIEdgeInsetsZero;
    }

    UIFont *fontThatFitsBounds = [self fontThatFitsBounds];
    CGSize textSize = [self.text sizeWithAttributes:@{
                                                      NSFontAttributeName : fontThatFitsBounds
                                                      }];
    CGSize actualSize = self.bounds.size;

    CGFloat exceedingWidth = actualSize.width = textSize.width;
    CGFloat exceedingHeight = actualSize.height - textSize.height;
    CGFloat exceedingHeightTop = exceedingHeight / 2.0f;
    CGFloat exceedingHeightBottom = MAX(0.0f, exceedingHeight / 2.0f + fontThatFitsBounds.descender);

    UIEdgeInsets insets = UIEdgeInsetsMake(
                                           exceedingHeightTop,
                                           0.0f,
                                           exceedingHeightBottom,
                                           0.0f
                                           );

    return insets;
}

- (UIFont *)fontThatFitsBounds
{
    CGSize currentSize = CGSizeZero;
    CGFloat fontSizeThatFits = self.font.pointSize + 1.0f;

    do {

        fontSizeThatFits = fontSizeThatFits - 1.0f; //try with one point smaller size

        NSDictionary *attributes = [self stringAttributesWithFontOfSize:fontSizeThatFits];
        currentSize = [self.text sizeWithAttributes:attributes];

    } while (currentSize.width > self.bounds.size.width ||
             currentSize.height > self.bounds.size.height);

    return [self.font fontWithSize:fontSizeThatFits];
}

- (NSDictionary *)stringAttributesWithFontOfSize:(CGFloat)fontSize
{
    NSMutableParagraphStyle * paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineBreakMode = self.lineBreakMode;
    paragraphStyle.alignment = self.textAlignment;

    NSDictionary *attributes = @{
                                 NSFontAttributeName : [self.font fontWithSize:fontSize],
                                 NSParagraphStyleAttributeName : paragraphStyle
                                 };

    return attributes;
}

@end

Demo project can be downloaded for here