苹果并未提供Label顶端对齐的设置，但是我们经常会有这种需求，现提供一个方法。
//.h文件
typedef enum VerticalAlignment {
VerticalAlignmentTop,
VerticalAlignmentMiddle,
VerticalAlignmentBottom,
} VerticalAlignment;
@interface VerticallyAlignedLabel : UILabel {
@private
VerticalAlignment verticalAlignment_;
}
@property (nonatomic, assign) VerticalAlignment verticalAlignment;
//.m文件
@synthesize verticalAlignment = verticalAlignment_;
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
self.verticalAlignment = VerticalAlignmentMiddle;
}
return self;
}
- (void)setVerticalAlignment:(VerticalAlignment)verticalAlignment {
verticalAlignment_ = verticalAlignment;
[self setNeedsDisplay];
}
- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines {
CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
switch (self.verticalAlignment) {
case VerticalAlignmentTop:
textRect.origin.y = bounds.origin.y;
break;
case VerticalAlignmentBottom:
textRect.origin.y = bounds.origin.y + bounds.size.height - textRect.size.height;
break;
case VerticalAlignmentMiddle:
// Fall through.
default:
textRect.origin.y = bounds.origin.y + (bounds.size.height - textRect.size.height) / 2.0;
}
return textRect;
}
-(void)drawTextInRect:(CGRect)requestedRect {
CGRect actualRect = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];
[super drawTextInRect:actualRect];
}
除了可以顶端对齐还可以底端对齐，但估计这种需求不多。
调用时只需继承这个label，然后调用
[label setContentMode:UIViewContentModeTop];
是不是很简单呢？
