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
我编写了一个util函数来实现这个目的。你可以看看:
// adjust the height of a multi-line label to make it align vertical with top + (void) alignLabelWithTop:(UILabel *)label { CGSize maxSize = CGSizeMake(label.frame.size.width, 999); label.adjustsFontSizeToFitWidth = NO; // get actual height CGSize actualSize = [label.text sizeWithFont:label.font constrainedToSize:maxSize lineBreakMode:label.lineBreakMode]; CGRect rect = label.frame; rect.size.height = actualSize.height; label.frame = rect; }
.如何使用?(如果lblHello是由Interface builder创建的,所以我跳过了一些UILabel属性的详细信息)
lblHello.text = @"Hello World! Hello World! Hello World! Hello World! Hello World! Hello World! Hello World! Hello World!"; lblHello.numberOfLines = 5; [Utils alignLabelWithTop:lblHello];
我还在博客上写了一篇文章:http://fstoke.me/blog/?p=2819
其他回答
创建UILabel的子类。就像一个魅力:
// TopLeftLabel.h
#import <Foundation/Foundation.h>
@interface TopLeftLabel : UILabel
{
}
@end
// TopLeftLabel.m
#import "TopLeftLabel.h"
@implementation TopLeftLabel
- (id)initWithFrame:(CGRect)frame
{
return [super initWithFrame:frame];
}
- (CGRect)textRectForBounds:(CGRect)bounds limitedToNumberOfLines:(NSInteger)numberOfLines
{
CGRect textRect = [super textRectForBounds:bounds limitedToNumberOfLines:numberOfLines];
textRect.origin.y = bounds.origin.y;
return textRect;
}
-(void)drawTextInRect:(CGRect)requestedRect
{
CGRect actualRect = [self textRectForBounds:requestedRect limitedToNumberOfLines:self.numberOfLines];
[super drawTextInRect:actualRect];
}
@end
正如这里所讨论的。
快速用户界面
在SwiftUI中,所有视图的大小通常为适合其内容的大小,但如果明确使用框架修饰符,则可以使用框架的对齐参数:
Text("Text")
.background(Color.red)
.frame(width: 100, height: 200, alignment: .top)
此外,如果使用任何类型的“堆栈”来排列视图,所有视图都有一个类似于框架的参数,称为对齐:
ZStack(alignment: .top) {
Color.red
Text("Text")
.background(Color.red)
}
我接受了这里的建议,并创建了一个可以包装UILabel的视图,它将调整大小并设置行数,使其顶部对齐。只需将UILabel作为子视图:
@interface TopAlignedLabelContainer : UIView
{
}
@end
@implementation TopAlignedLabelContainer
- (void)layoutSubviews
{
CGRect bounds = self.bounds;
for (UILabel *label in [self subviews])
{
if ([label isKindOfClass:[UILabel class]])
{
CGSize fontSize = [label.text sizeWithFont:label.font];
CGSize textSize = [label.text sizeWithFont:label.font
constrainedToSize:bounds.size
lineBreakMode:label.lineBreakMode];
label.numberOfLines = textSize.height / fontSize.height;
label.frame = CGRectMake(0, 0, textSize.width,
fontSize.height * label.numberOfLines);
}
}
}
@end
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];
}
不要大惊小怪
@interface MFTopAlignedLabel : UILabel
@end
@implementation MFTopAlignedLabel
- (void)drawTextInRect:(CGRect) rect
{
NSAttributedString *attributedText = [[NSAttributedString alloc] initWithString:self.text attributes:@{NSFontAttributeName:self.font}];
rect.size.height = [attributedText boundingRectWithSize:rect.size
options:NSStringDrawingUsesLineFragmentOrigin
context:nil].size.height;
if (self.numberOfLines != 0) {
rect.size.height = MIN(rect.size.height, self.numberOfLines * self.font.lineHeight);
}
[super drawTextInRect:rect];
}
@end
没有混乱,没有Objective-c,没有大惊小怪,只有Swift 3:
class VerticalTopAlignLabel: UILabel {
override func drawText(in rect:CGRect) {
guard let labelText = text else { return super.drawText(in: rect) }
let attributedText = NSAttributedString(string: labelText, attributes: [NSFontAttributeName: font])
var newRect = rect
newRect.size.height = attributedText.boundingRect(with: rect.size, options: .usesLineFragmentOrigin, context: nil).size.height
if numberOfLines != 0 {
newRect.size.height = min(newRect.size.height, CGFloat(numberOfLines) * font.lineHeight)
}
super.drawText(in: newRect)
}
}
雨燕4.2
class VerticalTopAlignLabel: UILabel {
override func drawText(in rect:CGRect) {
guard let labelText = text else { return super.drawText(in: rect) }
let attributedText = NSAttributedString(string: labelText, attributes: [NSAttributedString.Key.font: font])
var newRect = rect
newRect.size.height = attributedText.boundingRect(with: rect.size, options: .usesLineFragmentOrigin, context: nil).size.height
if numberOfLines != 0 {
newRect.size.height = min(newRect.size.height, CGFloat(numberOfLines) * font.lineHeight)
}
super.drawText(in: newRect)
}
}