控制UIlabel 垂直方向对齐方式的方法

最新推荐文章于 2025-09-05 16:34:31 发布

转载最新推荐文章于 2025-09-05 16:34:31 发布 · 55 阅读

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原文链接：http://www.cnblogs.com/liyufeng2013/p/UILabel.html

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#移动开发

本文详细介绍了如何通过Objective-C的Category特性，修改UILabel的绘制代码，实现垂直对齐顶部和底部的功能。包括具体实现步骤、代码示例及运行效果展示。

最正统的方法，利用objective-c的category特性，修改UILabel的绘制代码。示例代码如下：

// -- file: UILabel+VerticalAlign.h
#pragma mark VerticalAlign
@interface UILabel (VerticalAlign)
- (void)alignTop;
- (void)alignBottom;
@end
// -- file: UILabel+VerticalAlign.m
@implementation UILabel (VerticalAlign)
- (void)alignTop {
    CGSize fontSize = [self.text sizeWithFont:self.font];
    double finalHeight = fontSize.height * self.numberOfLines;
    double finalWidth = self.frame.size.width;    //expected width of label
    CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
    int newLinesToPad = (finalHeight  - theStringSize.height) / fontSize.height;
    for(int i=0; i<newLinesToPad; i++)
        self.text = [self.text stringByAppendingString:@"\n "];
}
- (void)alignBottom {
    CGSize fontSize = [self.text sizeWithFont:self.font];
    double finalHeight = fontSize.height * self.numberOfLines;
    double finalWidth = self.frame.size.width;    //expected width of label
    CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
    int newLinesToPad = (finalHeight  - theStringSize.height) / fontSize.height;
    for(int i=0; i<newLinesToPad; i++)
        self.text = [NSString stringWithFormat:@" \n%@",self.text];
}
@end