我有一个UILabel,它有两行文字的空间。有时,当文本太短时,此文本会显示在标签的垂直中心。
如何垂直对齐文本,使其始终位于UILabel的顶部?
我有一个UILabel,它有两行文字的空间。有时,当文本太短时,此文本会显示在标签的垂直中心。
如何垂直对齐文本,使其始终位于UILabel的顶部?
当前回答
在发布的所有其他解决方案的基础上,我创建了一个简单的小UILabel子类,在设置其对齐属性时将为您处理垂直对齐。这还将在方向更改时更新标签,将高度约束到文本,并将标签的宽度保持在其原始大小。
.h
@interface VAlignLabel : UILabel
@property (nonatomic, assign) WBZVerticalAlignment alignment;
@end
.m
-(void)setAlignment:(WBZVerticalAlignment)alignment{
_alignment = alignment;
CGSize s = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(self.frame.size.width, 9999) lineBreakMode:NSLineBreakByWordWrapping];
switch (_alignment)
{
case wbzLabelAlignmentVerticallyTop:
self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width, s.height);
break;
case wbzLabelAlignmentVerticallyMiddle:
self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y + (self.frame.size.height - s.height)/2, self.frame.size.width, s.height);
break;
case wbzLabelAlignmentVerticallyBottom:
self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y + (self.frame.size.height - s.height), self.frame.size.width, s.height);
break;
default:
break;
}
}
-(void)layoutSubviews{
[self setAlignment:self.alignment];
}
其他回答
我发现这个问题的答案现在有点过时了,所以为汽车布局爱好者添加这个。
自动布局使这个问题变得非常微不足道。假设我们要将标签添加到UIView*视图中,以下代码将完成此操作:
UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
[label setText:@"Some text here"];
[label setTranslatesAutoresizingMaskIntoConstraints:NO];
[view addSubview:label];
[view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[label]|" options:0 metrics:nil views:@{@"label": label}]];
[view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[label]" options:0 metrics:nil views:@{@"label": label}]];
标签的高度将自动计算(使用其intrinsicContentSize),标签将在视图顶部水平放置。
我希望有一个标签能够有多行,最小字体大小,并在父视图中水平和垂直居中。我以编程方式将标签添加到视图中:
- (void) customInit {
// Setup label
self.label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
self.label.numberOfLines = 0;
self.label.lineBreakMode = UILineBreakModeWordWrap;
self.label.textAlignment = UITextAlignmentCenter;
// Add the label as a subview
self.autoresizesSubviews = YES;
[self addSubview:self.label];
}
然后当我想更改标签的文本时。。。
- (void) updateDisplay:(NSString *)text {
if (![text isEqualToString:self.label.text]) {
// Calculate the font size to use (save to label's font)
CGSize textConstrainedSize = CGSizeMake(self.frame.size.width, INT_MAX);
self.label.font = [UIFont systemFontOfSize:TICKER_FONT_SIZE];
CGSize textSize = [text sizeWithFont:self.label.font constrainedToSize:textConstrainedSize];
while (textSize.height > self.frame.size.height && self.label.font.pointSize > TICKER_MINIMUM_FONT_SIZE) {
self.label.font = [UIFont systemFontOfSize:self.label.font.pointSize-1];
textSize = [ticker.blurb sizeWithFont:self.label.font constrainedToSize:textConstrainedSize];
}
// In cases where the frame is still too large (when we're exceeding minimum font size),
// use the views size
if (textSize.height > self.frame.size.height) {
textSize = [text sizeWithFont:self.label.font constrainedToSize:self.frame.size];
}
// Draw
self.label.frame = CGRectMake(0, self.frame.size.height/2 - textSize.height/2, self.frame.size.width, textSize.height);
self.label.text = text;
}
[self setNeedsDisplay];
}
希望这对某人有所帮助!
FXLabel(在github上)通过将label.contentMode设置为UIViewContentModeTop来实现这一点。这个组件不是我制造的,但它是我经常使用的组件,具有大量的功能,而且似乎工作得很好。
子类UILabel并约束绘图矩形,如下所示:
- (void)drawTextInRect:(CGRect)rect
{
CGSize sizeThatFits = [self sizeThatFits:rect.size];
rect.size.height = MIN(rect.size.height, sizeThatFits.height);
[super drawTextInRect:rect];
}
我尝试了涉及换行填充的解决方案,在某些情况下遇到了错误的行为。根据我的经验,如上所述约束绘图矩形比使用numberOfLines更容易。
P.S.你可以想象一下这样轻松地支持UIViewContentMode:
- (void)drawTextInRect:(CGRect)rect
{
CGSize sizeThatFits = [self sizeThatFits:rect.size];
if (self.contentMode == UIViewContentModeTop) {
rect.size.height = MIN(rect.size.height, sizeThatFits.height);
}
else if (self.contentMode == UIViewContentModeBottom) {
rect.origin.y = MAX(0, rect.size.height - sizeThatFits.height);
rect.size.height = MIN(rect.size.height, sizeThatFits.height);
}
[super drawTextInRect:rect];
}
使用textRect(对于边界:limitedToNumberOfLines:)。
class TopAlignedLabel: UILabel {
override func drawText(in rect: CGRect) {
let textRect = super.textRect(forBounds: bounds, limitedToNumberOfLines: numberOfLines)
super.drawText(in: textRect)
}
}