如何让 UILabel 显示轮廓文本? [英] How do I make UILabel display outlined text?

问题描述

我想要的只是在我的白色 UILabel 文本周围有一个 1 像素的黑色边框.

All I want is a one pixel black border around my white UILabel text.

我已经使用下面的代码对 UILabel 进行了子类化，这些代码是我从一些相关的在线示例中笨拙地拼凑而成的.它可以工作，但它非常非常慢(除了在模拟器上)而且我也无法让它垂直居中文本(所以我暂时硬编码了最后一行的 y 值).啊哈！

I got as far as subclassing UILabel with the code below, which I clumsily cobbled together from a few tangentially related online examples. And it works but it's very, very slow (except on the simulator) and I couldn't get it to center the text vertically either (so I hard-coded the y value on the last line temporarily). Ahhhh!

void ShowStringCentered(CGContextRef gc, float x, float y, const char *str) {
    CGContextSetTextDrawingMode(gc, kCGTextInvisible);
    CGContextShowTextAtPoint(gc, 0, 0, str, strlen(str));
    CGPoint pt = CGContextGetTextPosition(gc);

    CGContextSetTextDrawingMode(gc, kCGTextFillStroke);

    CGContextShowTextAtPoint(gc, x - pt.x / 2, y, str, strlen(str));
}


- (void)drawRect:(CGRect)rect{

    CGContextRef theContext = UIGraphicsGetCurrentContext();
    CGRect viewBounds = self.bounds;

    CGContextTranslateCTM(theContext, 0, viewBounds.size.height);
    CGContextScaleCTM(theContext, 1, -1);

    CGContextSelectFont (theContext, "Helvetica", viewBounds.size.height,  kCGEncodingMacRoman);

    CGContextSetRGBFillColor (theContext, 1, 1, 1, 1);
    CGContextSetRGBStrokeColor (theContext, 0, 0, 0, 1);
    CGContextSetLineWidth(theContext, 1.0);

    ShowStringCentered(theContext, rect.size.width / 2.0, 12, [[self text] cStringUsingEncoding:NSASCIIStringEncoding]);
}

我只是有一种唠叨的感觉，我忽略了一种更简单的方法来做到这一点.也许通过覆盖drawTextInRect"，但我似乎无法让 drawTextInRect 屈服于我的意愿，尽管我专注地盯着它并且真的很难皱眉.

I just have a nagging feeling that I'm overlooking a simpler way to do this. Perhaps by overriding "drawTextInRect", but I can't seem to get drawTextInRect to bend to my will at all despite staring at it intently and frowning really really hard.

推荐答案

我能够通过覆盖 drawTextInRect 来做到这一点:

I was able to do it by overriding drawTextInRect:

- (void)drawTextInRect:(CGRect)rect {

  CGSize shadowOffset = self.shadowOffset;
  UIColor *textColor = self.textColor;

  CGContextRef c = UIGraphicsGetCurrentContext();
  CGContextSetLineWidth(c, 1);
  CGContextSetLineJoin(c, kCGLineJoinRound);

  CGContextSetTextDrawingMode(c, kCGTextStroke);
  self.textColor = [UIColor whiteColor];
  [super drawTextInRect:rect];

  CGContextSetTextDrawingMode(c, kCGTextFill);
  self.textColor = textColor;
  self.shadowOffset = CGSizeMake(0, 0);
  [super drawTextInRect:rect];

  self.shadowOffset = shadowOffset;

}

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