IOS系統框架中UILabel的屬性textAlignment只調整水平方向的居中,居左,居右,而沒有垂直方向的調整。因此要自定義一個繼承自UILabel的類,在類的實現文件中進行文字的重繪,達到垂直方向的位置調整。框架
新建一個類文件,繼承自UILabel,頭文件以下:字體
#import <UIKit/UIKit.h> typedef NS_ENUM(NSInteger,VerticalAlignment){ VerticalAlignmentTop, VerticalAlignmentMiddle, VerticalAlignmentBottom }; @interface FSVerticallyAlignedLabel : UILabel @property (nonatomic,assign) VerticalAlignment verticalAlignment; @end
在.m文件中,實現verticalAlignment的設置方法atom
@implementation FSVerticallyAlignedLabel - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { self.verticalAlignment = VerticalAlignmentMiddle; } return self; } /** * 設置屬性方法 * * @param verticalAlignment 垂直調整位置 */ - (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment { _verticalAlignment = verticalAlignment; [self setNeedsDisplay]; } /** * 計算文字的矩形區域 * * @param bounds label矩形區域 * @param numberOfLines 行數 * * @return 返回文字所佔的矩形區域 */ - (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines { CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines]; //經過設定字體區域的y值來調整垂直位置 switch (self.verticalAlignment) { case VerticalAlignmentTop: textRect.origin.y = bounds.origin.y; break; case VerticalAlignmentMiddle: textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0; break; case VerticalAlignmentBottom: textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height; break; } return textRect; } //重寫父類方法 - (void)drawTextInRect:(CGRect)rect { CGRect actualRect = [self textRectForBounds:rect limitedToNumberOfLines:self.numberOfLines]; [super drawTextInRect:actualRect]; } @end