ios - 渐变颜色在非英语语言的 UILabel 中被截断

Question

我想为 UILabel 中的文本设置渐变颜色，但发现如果文本是非英语语言，渐变颜色会被截断。这是错误吗？

代码如下:

- (void)viewDidLoad {
    [super viewDidLoad];
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 100, 0, 0)];
    label.font = [UIFont boldSystemFontOfSize:30];
    label.text = @"Your Name";
    [label sizeToFit];

    UIImage *gradientImage = [self.class gradientImageWithSize:label.frame.size beginColor:UIColor.redColor endColor:UIColor.yellowColor];

    label.textColor = [UIColor colorWithPatternImage:gradientImage];
    [self.view addSubview:label];
}

+ (UIImage *)gradientImageWithSize:(CGSize)size beginColor:(UIColor *)beginColor endColor:(UIColor *)endColor {
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.colors = @[(__bridge id)beginColor.CGColor, (__bridge id)endColor.CGColor];
    gradientLayer.startPoint = CGPointMake(0, 0.5);
    gradientLayer.endPoint = CGPointMake(1, 0.5);
    gradientLayer.frame = CGRectMake(0, 0, size.width, size.height);

    UIGraphicsBeginImageContext(gradientLayer.bounds.size);
    [gradientLayer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

只需将 label.text 替换为:

label.text = @"你的名字";

Or

label.text = @"君の名は";

然后它发生了。有谁知道为什么吗？

Answer 1

我认为这是 UIKit 的错误。当标签没有英文字符时，图 block 的大小会出错。

如果你想屏蔽标签上的渐变颜色，只需为你的标签使用屏蔽 View 。

objective-c

- (void)viewDidLoad {
    [super viewDidLoad];

    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 100, 0, 0)];
    label.font = [UIFont boldSystemFontOfSize:30];
    label.text = @"君の名は";
    [label sizeToFit];


    UIView *gradientView = [[UIView alloc] initWithFrame:label.frame];
    label.frame = gradientView.bounds;

    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.frame = gradientView.bounds;
    gradientLayer.colors = @[(__bridge id)UIColor.redColor.CGColor, (__bridge id)UIColor.yellowColor.CGColor];
    gradientLayer.startPoint = CGPointMake(0, 0.5);
    gradientLayer.endPoint = CGPointMake(1, 0.5);

    [gradientView.layer addSublayer:gradientLayer];
    [gradientView addSubview:label];
    [gradientView setMaskView:label];
}

swift

override func viewDidLoad() {
    super.viewDidLoad()

    let label = UILabel(frame: CGRect(x: 10, y: 100, width: 0, height: 0))
    label.text = "君の名は"
    label.font = UIFont.boldSystemFont(ofSize: 30)
    label.sizeToFit()

    let gradientView = UIView(frame: label.frame)
    label.frame = gradientView.bounds
    let gradientLayer = CAGradientLayer()
    gradientLayer.frame = gradientView.bounds
    gradientLayer.colors = [UIColor.red.cgColor, UIColor.yellow.cgColor]
    gradientLayer.startPoint = CGPoint(x: 0, y: 0.5)
    gradientLayer.endPoint = CGPoint(x: 1, y: 0.5)

    gradientView.layer.addSublayer(gradientLayer)
    gradientView.addSubview(label)
    gradientView.mask = label

    self.view.addSubview(gradientView)
}