动态更改UILabel字体大小

Question

动态更改UILabel字体大小

213

我目前有一个 UILabel：

factLabel = [[UILabel alloc] initWithFrame:CGRectMake(20, 100, 280, 100)];
factLabel.text = @"some text some text some text some text";
factLabel.backgroundColor = [UIColor clearColor];
factLabel.lineBreakMode = UILineBreakModeWordWrap;
factLabel.numberOfLines = 10;
[self.view addSubview:factLabel];

在我的iOS应用的整个生命周期中，factLabel 会获取许多不同的值。有些是有多个句子的，有些只有5或6个单词。

我该如何设置 UILabel 来使字体大小随着文本内容的变化而自动调整，以便始终适合我定义的范围？

- CodeGuy

2

对于2016年，我真的相信唯一“好”的解决方案是使用“使用自动收缩”方法。使UILabel框实际大小，使字体填充UILabel，选择自动收缩，设置一个标题巨大的字体大小（300），并确保在最小/最大模拟器上进行测试。（因此，目前为止是4s / PadPro。）完整的解释：https://dev59.com/X1sW5IYBdhLWcg3wSVqM#35154493 这是今天唯一真正的解决方案。 - Fattie

12个回答

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- videolist · Answer 1

这是一个实现动态字体大小变化的UILabel子类的完整代码：

@interface SNTextLayer : CATextLayer

@end

@implementation SNTextLayer

- (void)drawInContext:(CGContextRef)ctx {
    // We override this to make text appear at the same vertical positon as in UILabel
    // (otherwise it's shifted tdown)
    CGFloat height = self.bounds.size.height;
    float fontSize = self.fontSize;
    // May need to adjust this somewhat if it's not aligned perfectly in your implementation
    float yDiff = (height-fontSize)/2 - fontSize/10;

    CGContextSaveGState(ctx);
    CGContextTranslateCTM(ctx, 0.0, yDiff);
    [super drawInContext:ctx];
     CGContextRestoreGState(ctx);
}

@end

@interface SNAnimatableLabel ()

@property CATextLayer* textLayer;

@end

@interface SNAnimatableLabel : UILabel

- (void)animateFontToSize:(CGFloat)fontSize withDuration:(double)duration;

@end



@implementation SNAnimatableLabel


- (void)awakeFromNib {
    [super awakeFromNib];
    _textLayer = [SNTextLayer new];
    _textLayer.backgroundColor = self.backgroundColor.CGColor;
    _textLayer.foregroundColor = self.textColor.CGColor;
    _textLayer.font = CGFontCreateWithFontName((CFStringRef)self.font.fontName);
    _textLayer.frame = self.bounds;
    _textLayer.string = self.text;
    _textLayer.fontSize = self.font.pointSize;
    _textLayer.contentsScale = [UIScreen mainScreen].scale;
    [_textLayer setPosition: CGPointMake(CGRectGetMidX(_textLayer.frame), CGRectGetMidY(_textLayer.frame))];
    [_textLayer setAnchorPoint: CGPointMake(0.5, 0.5)];
    [_textLayer setAlignmentMode: kCAAlignmentCenter];
    self.textColor = self.backgroundColor;
    // Blend text with background, so that it doens't interfere with textlayer text
    [self.layer addSublayer:_textLayer];
    self.layer.masksToBounds = NO;
}

- (void)setText:(NSString *)text {
    _textLayer.string = text;
    super.text = text;
}

- (void)layoutSubviews {
    [super layoutSubviews];
    // Need to enlarge the frame, otherwise the text may get clipped for bigger font sizes
    _textLayer.frame = CGRectInset(self.bounds, -5, -5);
}

- (void)animateFontToSize:(CGFloat)fontSize withDuration:(double)duration {
    [CATransaction begin];
    [CATransaction setAnimationDuration:duration];
    _textLayer.fontSize = fontSize;
    [CATransaction commit];
}

- aaroncatlin · Answer 2

这个解决方案适用于多行文本：

在阅读了几篇文章之后，我需要一个函数，可以自动缩放文本并调整行数，以最好地适应给定标签的大小。因此，我编写了一个函数。（例如，短字符串可以很好地适合一行，并使用大量标签框架，而长字符串会自动分成2或3行，并相应地调整大小）

请随意重复使用它并根据需要进行调整。确保在viewDidLayoutSubviews完成后调用它，以便设置初始标签框架。

+ (void)setFontForLabel:(UILabel *)label withMaximumFontSize:(float)maxFontSize andMaximumLines:(int)maxLines {
    int numLines = 1;
    float fontSize = maxFontSize;
    CGSize textSize; // The size of the text
    CGSize frameSize; // The size of the frame of the label
    CGSize unrestrictedFrameSize; // The size the text would be if it were not restricted by the label height
    CGRect originalLabelFrame = label.frame;

    frameSize = label.frame.size;
    textSize = [label.text sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize: fontSize]}];

    // Work out the number of lines that will need to fit the text in snug
    while (((textSize.width / numLines) / (textSize.height * numLines) > frameSize.width / frameSize.height) && (numLines < maxLines)) {
        numLines++;
    }

    label.numberOfLines = numLines;

    // Get the current text size
    label.font = [UIFont systemFontOfSize:fontSize];
    textSize = [label.text boundingRectWithSize:CGSizeMake(frameSize.width, CGFLOAT_MAX)
                                        options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                     attributes:@{NSFontAttributeName : label.font}
                                        context:nil].size;

    // Adjust the frame size so that it can fit text on more lines
    // so that we do not end up with truncated text
    label.frame = CGRectMake(label.frame.origin.x, label.frame.origin.y, label.frame.size.width, label.frame.size.width);

    // Get the size of the text as it would fit into the extended label size
    unrestrictedFrameSize = [label textRectForBounds:CGRectMake(0, 0, label.bounds.size.width, CGFLOAT_MAX) limitedToNumberOfLines:numLines].size;

    // Keep reducing the font size until it fits
    while (textSize.width > unrestrictedFrameSize.width || textSize.height > frameSize.height) {
        fontSize--;
        label.font = [UIFont systemFontOfSize:fontSize];
        textSize = [label.text boundingRectWithSize:CGSizeMake(frameSize.width, CGFLOAT_MAX)
                                            options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                         attributes:@{NSFontAttributeName : label.font}
                                            context:nil].size;
        unrestrictedFrameSize = [label textRectForBounds:CGRectMake(0, 0, label.bounds.size.width, CGFLOAT_MAX) limitedToNumberOfLines:numLines].size;
    }

    // Set the label frame size back to original
    label.frame = originalLabelFrame;
}