用UILabel文本掩码显示UIView

Question

我试图将UIView添加到UILabel，以便文本是视图的掩码，使我能够执行诸如动画文本背景之类的操作（就像在幻灯片上解锁标签一样锁屏）。

我打算这样做的方式是使用视图的layer上的mask属性将其掩盖为文本的形状。但是，我找不到一种方法将UILabel的文本形状设置为CALayer。

这甚至可能吗？我只能找到覆盖UILabel中的-(void)drawRect:方法的解决方案，但这不会给我太大的灵活性。

Answer 1

在IOS 8.0 UIView added the maskView property。现在，只需创建一个UILabel作为面膜使用的UIView：

的Objective-C：

UILabel* label = [[UILabel alloc] initWithFrame:self.view.frame]; 
label.text = @"Label Text"; 
label.font = [UIFont systemFontOfSize:70]; 
label.textAlignment = NSTextAlignmentCenter; 
label.textColor = [UIColor whiteColor]; 

UIView* overlayView = [[UIView alloc] initWithFrame:self.view.frame]; 
overlayView.backgroundColor = [UIColor blueColor]; 
overlayView.maskView = label; 
[self.view addSubview:overlayView]; 

斯威夫特2：

let label = UILabel.init(frame: view.frame) 
label.text = "Label Text" 
label.font = UIFont.systemFontOfSize(70) 
label.textAlignment = .Center 
label.textColor = UIColor.whiteColor() 

let overlayView = UIView.init(frame: view.frame) 
overlayView.backgroundColor = UIColor.blueColor() 
overlayView.maskView = label 

view.addSubview(overlayView) 

这就形成了一个清晰的UILabel与UIColor.blueColor()颜色取自overlayView。

Answer 2

mopsled's solution如果您为iOS 8+构建而更灵活。但是，如果您正在寻找iOS 8之前的答案，那就是。

---

感谢Linuxios指着我this question。关键是使用CATextLayer而不是UILabel。

目的-C：

CGRect textRect = {0, 100, self.view.frame.size.width, 100}; // rect to display the view in 

CATextLayer* textMask = [CATextLayer layer]; 
textMask.contentsScale = [UIScreen mainScreen].scale; // sets the layer's scale to the main screen scale 
textMask.frame = (CGRect){CGPointZero, textRect.size}; 
textMask.foregroundColor = [UIColor whiteColor].CGColor; // an opaque color so that the mask covers the text 
textMask.string = @"Text Mask"; // your text here 
textMask.font = (__bridge CFTypeRef _Nullable)([UIFont systemFontOfSize:30]); // your font here 
textMask.alignmentMode = kCAAlignmentCenter; // centered text 

UIView* view = [[UIView alloc] initWithFrame:textRect]; 
view.backgroundColor = [UIColor blueColor]; 
view.layer.mask = textMask; // mask the view to the textMask 
[self.view addSubview:view]; 

夫特：

let textRect = CGRect(x: 0, y: 100, width: view.frame.size.width, height: 100) // rect to display the view in 

let textMask = CATextLayer() 
textMask.contentsScale = UIScreen.mainScreen().scale // sets the layer's scale to the main screen scale 
textMask.frame = CGRect(origin: CGPointZero, size: textRect.size) 
textMask.foregroundColor = UIColor.whiteColor().CGColor // an opaque color so that the mask covers the text 
textMask.string = "Text Mask" // your text here 
textMask.font = UIFont.systemFontOfSize(30) // your font here 
textMask.alignmentMode = kCAAlignmentCenter // centered text 

let bgView = UIView(frame: textRect) 
bgView.backgroundColor = UIColor.blueColor() 
bgView.layer.mask = textMask // mask the view to the textMask 
view.addSubview(bgView) 

Answer 3

我创建了自定义maskLabel。

检查答案 https://stackoverflow.com/a/47105664/7371852

这是结果。