CATextLayer 和字符之间的跟踪/间距

Question

我正在使用 CATextLayer，为了在 iOS 中使用自定义字体，我知道有一种简单的方法可以通过 Fonts provided by application 使用自定义字体，但这是不同的字体。我想知道有没有办法改变每个字符之间的间距？我没有找到任何财产这样做！

已编辑：

- (void)viewWillAppear:(BOOL)animated {
    CTFontRef font = [self newCustomFontWithName:@"yeki" 
                                          ofType:@"ttf" 
                                      attributes:[NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:16.f] 
                                                                             forKey:(NSString *)kCTFontSizeAttribute]];


    CGRect screenBounds = [[UIScreen mainScreen] bounds];

    normalTextLayer_ = [[CATextLayer alloc] init];
    normalTextLayer_.font = font;
    normalTextLayer_.string = str;
    normalTextLayer_.wrapped = YES;
    normalTextLayer_.foregroundColor = [[UIColor purpleColor] CGColor];
    normalTextLayer_.fontSize = 50.f;
    normalTextLayer_.alignmentMode =  kCAAlignmentRight;

    normalTextLayer_.frame = CGRectMake(0.f,100.f, screenBounds.size.width, screenBounds.size.height /1.f);
    [self.view.layer addSublayer:normalTextLayer_];
    CFRelease(font);
}

Answer 1

您可以为图层分配NSAttributedString（或NSMutableAttributedString）而不是普通的NSString，并使用kCTKernAttributeName 属性（请参阅Core Text String Attributes Reference）来调整字距调整。

例子：

CTFontRef font = CTFontCreateWithName(CFSTR("Helvetica"), 30, NULL);
NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:
                            (id)font, kCTFontAttributeName, 
                            [NSNumber numberWithFloat:15.0], kCTKernAttributeName, 
                            (id)[[UIColor greenColor] CGColor], kCTForegroundColorAttributeName, nil];
NSAttributedString *attributedString = [[[NSAttributedString alloc] initWithString:@"Hello World" attributes:attributes] autorelease];
CFRelease(font);
myTextLayer.string = attributedString;

这应该会在 Helvetica 30 中为您提供绿色文本，并增加字符间距。