在CATextLayer中顯示屬性字符串

Question

我有一個簡單的示例應用程序，我創建了一個CATextLayer並將其string屬性設置爲NSAttributedString。然後我將CATextLayer添加到視圖中。

#import <CoreText/CoreText.h> 
#import <QuartzCore/QuartzCore.h> 

@implementation ViewController 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    CTFontRef fontFace = CTFontCreateWithName((__bridge CFStringRef)(@"HelfaSemiBold"), 24.0, NULL); 
    NSMutableDictionary *attributes = [[NSMutableDictionary alloc] init]; 
    [attributes setObject:(__bridge id)fontFace forKey:(NSString*)kCTFontAttributeName]; 
    [attributes setObject:[UIColor blueColor] forKey:(NSString*)kCTForegroundColorAttributeName]; 
    NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:@"Lorem Ipsum" attributes:attributes]; 

    CATextLayer *textLayer = [CATextLayer layer]; 
    textLayer.backgroundColor = [UIColor whiteColor].CGColor; 
    textLayer.frame = CGRectMake(20, 20, 200, 100); 
    textLayer.contentsScale = [[UIScreen mainScreen] scale]; 
    textLayer.string = attrStr; 

    [self.view.layer addSublayer:textLayer]; 
} 

這在模擬器中很好用，除了文本是黑色而不是藍色。在設備上運行時，所有內容都會顯示在模擬器上，但它會在控制檯中生成以下兩個錯誤。

<Error>: CGContextSetFillColorWithColor: invalid context 0x0 
<Error>: CGContextSetStrokeColorWithColor: invalid context 0x0 

我應該在某處設置CGContext嗎？我是否設置了屬性錯誤？我完全在錯誤的軌道上。請注意，這是一個iOS 5.x應用程序，我想使用CATextLayer出於性能原因。真正的應用程序將有許多CATextLayer s。

Answer 1

必須使用CGColor，而不是UIColor爲kCTForegroundColorAttributeName：

[attributes setObject:(__bridge id)[UIColor blueColor].CGColor 
       forKey:(NSString *)kCTForegroundColorAttributeName]; 

Answer 2

我轉換這斯威夫特3，並把它裏面SpriteKit還有：

import QuartzCore 
import SpriteKit 

class GameScene: SKScene { 

    var textLayer = CATextLayer() 

    func helloWord() { 
    let fontFace = CTFontCreateWithName((("HelfaSemiBold") as CFString), 
             24.0, 
             nil) 
    var attributes: [AnyHashable: Any]? = [:] 
    attributes?[(kCTFontAttributeName as String)] = fontFace 
    attributes?[(kCTForegroundColorAttributeName as String)] = UIColor.blue.cgColor 

    let attrStr = NSAttributedString(string: "Hello Attributed Word!", 
            attributes: attributes as! [String : Any]?) 

    textLayer.backgroundColor = UIColor.white.cgColor 
    textLayer.frame = CGRect(x: CGFloat(50), y: CGFloat(200), 
          width: CGFloat(300), height: CGFloat(100)) 
    textLayer.contentsScale = UIScreen.main.scale 
    textLayer.string = attrStr 
    self.view?.layer.addSublayer(textLayer) 
    } 

    override func didMove(to view: SKView) { 
    helloWord() 
    } 
}