iPhone - 如何在矩形中间绘制文本

Question

是否有方法在矩形的中间绘制文本.我可以找到各种对齐方式,但我尝试过的任何内容都不能将文本垂直居中.

有没有一种简单的方法可以做到这一点,或者是否有某种方法可以使矩形居中然后绘制？

我正在直接绘制CGContext,尝试使用NSString :: drawWithRect或类似的东西,因为我真的不想添加一个Label来呈现一些基本文本.

Answer 1

好吧,font属性pointSize直接对应于NSString绘制的高度(以像素为单位)UIFont,因此您的公式将是这样的:

- (void) drawString: (NSString*) s 
           withFont: (UIFont*) font 
             inRect: (CGRect) contextRect {

    CGFloat fontHeight = font.pointSize;
    CGFloat yOffset = (contextRect.size.height - fontHeight) / 2.0;

    CGRect textRect = CGRectMake(0, yOffset, contextRect.size.width, fontHeight);

    [s drawInRect: textRect 
         withFont: font 
    lineBreakMode: UILineBreakModeClip 
        alignment: UITextAlignmentCenter];
}

UITextAlignmentCenter处理horizontal居中,所以我们使用contextRect的全宽.在lineBreakMode可以任何你喜欢的.

Answer 2

这是iOS7.0 +的更新版本.

我还通过使用sizeWithAttributes:返回文本边界的方法改进了上述答案,使您能够在绘制文本之前正确定位文本.如果您使用不同大小的字体或使用不同的字体,则无需对任何调整进行硬编码.

- (void) drawString: (NSString*) s
           withFont: (UIFont*) font
             inRect: (CGRect) contextRect {

    /// Make a copy of the default paragraph style
    NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    /// Set line break mode
    paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;
    /// Set text alignment
    paragraphStyle.alignment = NSTextAlignmentCenter;

    NSDictionary *attributes = @{ NSFontAttributeName: font,
                                  NSForegroundColorAttributeName: [UIColor whiteColor],
                                  NSParagraphStyleAttributeName: paragraphStyle };

    CGSize size = [s sizeWithAttributes:attributes];

    CGRect textRect = CGRectMake(contextRect.origin.x + floorf((contextRect.size.width - size.width) / 2),
                                 contextRect.origin.y + floorf((contextRect.size.height - size.height) / 2),
                                 size.width,
                                 size.height);

    [s drawInRect:textRect withAttributes:attributes];
}

Answer 3

斯威夫特 5

static func draw(_ text: String, _ rect: CGRect, _ font: UIFont) {

    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.alignment = .center
    let attributes = [
        NSAttributedString.Key.paragraphStyle: paragraphStyle,
        NSAttributedString.Key.font: font,
        NSAttributedString.Key.foregroundColor: UIColor.red
    ]
    NSAttributedString(string: text, attributes: attributes).draw(in: rect.insetBy(dx: 0, dy: (rect.height - font.pointSize)/2))
}

如果要绘制多条线，

 func drawMutipleLine(text: String = "Good morning how \nare you ,  fine, thank\nyou good day. uck wood?", 
                    _ rect: CGRect, 
                      font: UIFont =  UIFont(name: "HelveticaNeue-Thin", size: 15)!) -> UIImage {

    let renderer = UIGraphicsImageRenderer(size: rect.size)
    let image = renderer.image { ctx in
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.alignment = .center
        let font = UIFont(name: "HelveticaNeue-Thin", size: 15)!
        let attributes = [NSAttributedString.Key.font:font, NSAttributedString.Key.paragraphStyle: paragraphStyle]
        let numLines = text.split(separator: "\n").count + 1
        NSAttributedString(string: text, attributes: attributes).draw(in: rect.insetBy(dx: 0, dy: (rect.height - font.pointSize * CGFloat(numLines))/2))
    }
    return image
}