iPhone CATextLayer不显示其文本

Question

我只是想CATextlayer在一个UIView图层中添加一个.但是,根据以下代码,我只得到CATextlayer要显示的背景颜色UIView,没有任何文字.只是想知道我错过了显示文字的内容.

任何人都可以提供提示/样品如何使用CATextlayer？

  - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
        if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
            // Custom initialization

            CATextLayer *TextLayer = [CATextLayer layer];
            TextLayer.bounds = CGRectMake(0.0f, 0.0f, 100.0f, 100.0f);
            TextLayer.string = @"Test";
            TextLayer.font = [UIFont boldSystemFontOfSize:18].fontName;
            TextLayer.backgroundColor = [UIColor blackColor].CGColor;
            TextLayer.wrapped = NO;

            //TextLayer.backgroundColor = [UIColor blueColor];
            self.view = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 100.0f, 100.0f)];
            self.view.backgroundColor = [UIColor blueColor];
            [self.view.layer addSublayer:TextLayer];
            [self.view.layer layoutSublayers];

        }
        return self;
    }

Answer 1

对于iOS 5及更高版本,可以使用CATextLayer,如下所示:

CATextLayer *textLayer = [CATextLayer layer];
textLayer.frame = CGRectMake(144, 42, 76, 21);
textLayer.font = CFBridgingRetain([UIFont boldSystemFontOfSize:18].fontName);
textLayer.fontSize = 18;
textLayer.foregroundColor = [UIColor redColor].CGColor;
textLayer.backgroundColor = [UIColor yellowColor].CGColor;
textLayer.alignmentMode = kCAAlignmentCenter;
textLayer.string = @"BAC";
[self.view.layer addSublayer:textLayer];

您可以在任何您喜欢的功能中添加此代码.特别是在这里正确分配字体是必要的,否则无论你设置什么textColor,你的CATextLayer都会呈现为黑色.

Answer 2

将您的代码更改为:

CATextLayer *TextLayer = [CATextLayer layer];
TextLayer.bounds = CGRectMake(0.0f, 0.0f, 100.0f, 100.0f);
TextLayer.string = @"Test";
TextLayer.font = [UIFont boldSystemFontOfSize:18].fontName;
TextLayer.backgroundColor = [UIColor blackColor].CGColor;
TextLayer.position = CGPointMake(80.0, 80.0f);
TextLayer.wrapped = NO;
[self.view.layer addSublayer:TextLayer];

您还应该在视图控制器的-viewDidLoad中执行此操作.这样您就知道您的视图已加载且有效,现在可以添加图层.

Answer 3

您应该（与直觉相反）在初始化完成后或每当您希望它绘制文本时textLayer.display()调用或 。textLayer.displayIfNeeded()

Answer 4

根据文档， a 的默认文本颜色CATextLayer是白色。白底白字很难看清。