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
Swift 2.0版本:
在空Swift文件中生成常量枚举值。
// AppRef.swift
import UIKit
import Foundation
enum UILabelTextPositions : String {
case VERTICAL_ALIGNMENT_TOP = "VerticalAlignmentTop"
case VERTICAL_ALIGNMENT_MIDDLE = "VerticalAlignmentMiddle"
case VERTICAL_ALIGNMENT_BOTTOM = "VerticalAlignmentBottom"
}
使用UILabel扩展:
创建一个空的Swift类并命名它
// AppExtensions.swift
import Foundation
import UIKit
extension UILabel{
func makeLabelTextPosition (sampleLabel :UILabel?, positionIdentifier : String) -> UILabel
{
let rect = sampleLabel!.textRectForBounds(bounds, limitedToNumberOfLines: 0)
switch positionIdentifier
{
case "VerticalAlignmentTop":
sampleLabel!.frame = CGRectMake(bounds.origin.x+5, bounds.origin.y, rect.size.width, rect.size.height)
break;
case "VerticalAlignmentMiddle":
sampleLabel!.frame = CGRectMake(bounds.origin.x+5,bounds.origin.y + (bounds.size.height - rect.size.height) / 2,
rect.size.width, rect.size.height);
break;
case "VerticalAlignmentBottom":
sampleLabel!.frame = CGRectMake(bounds.origin.x+5, bounds.origin.y + (bounds.size.height - rect.size.height),rect.size.width, rect.size.height);
break;
default:
sampleLabel!.frame = bounds;
break;
}
return sampleLabel!
}
}
用法:
myMessageLabel.makeLabelTextPosition(messageLabel, positionIdentifier: UILabelTextPositions.VERTICAL_ALIGNMENT_TOP.rawValue)
其他回答
这是一个旧的解决方案,在iOS上使用自动布局>=6
我的解决方案:
自行拆分线条(忽略标签换行设置)自己绘制线(忽略标签对齐)
@interface UITopAlignedLabel : UILabel
@end
@implementation UITopAlignedLabel
#pragma mark Instance methods
- (NSArray*)splitTextToLines:(NSUInteger)maxLines {
float width = self.frame.size.width;
NSArray* words = [self.text componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSMutableArray* lines = [NSMutableArray array];
NSMutableString* buffer = [NSMutableString string];
NSMutableString* currentLine = [NSMutableString string];
for (NSString* word in words) {
if ([buffer length] > 0) {
[buffer appendString:@" "];
}
[buffer appendString:word];
if (maxLines > 0 && [lines count] == maxLines - 1) {
[currentLine setString:buffer];
continue;
}
float bufferWidth = [buffer sizeWithFont:self.font].width;
if (bufferWidth < width) {
[currentLine setString:buffer];
}
else {
[lines addObject:[NSString stringWithString:currentLine]];
[buffer setString:word];
[currentLine setString:buffer];
}
}
if ([currentLine length] > 0) {
[lines addObject:[NSString stringWithString:currentLine]];
}
return lines;
}
- (void)drawRect:(CGRect)rect {
if ([self.text length] == 0) {
return;
}
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, self.textColor.CGColor);
CGContextSetShadowWithColor(context, self.shadowOffset, 0.0f, self.shadowColor.CGColor);
NSArray* lines = [self splitTextToLines:self.numberOfLines];
NSUInteger numLines = [lines count];
CGSize size = self.frame.size;
CGPoint origin = CGPointMake(0.0f, 0.0f);
for (NSUInteger i = 0; i < numLines; i++) {
NSString* line = [lines objectAtIndex:i];
if (i == numLines - 1) {
[line drawAtPoint:origin forWidth:size.width withFont:self.font lineBreakMode:UILineBreakModeTailTruncation];
}
else {
[line drawAtPoint:origin forWidth:size.width withFont:self.font lineBreakMode:UILineBreakModeClip];
}
origin.y += self.font.lineHeight;
if (origin.y >= size.height) {
return;
}
}
}
@end
雨燕5
这里是从左上角开始渲染文本,并保持可能调整的文本大小。
final class TopAlignedLabel: UILabel {
override func drawText(in rect: CGRect) {
super.drawText(in: .init(
origin: .zero,
size: textRect(
forBounds: rect,
limitedToNumberOfLines: numberOfLines
).size
))
}
}
设置新文本:myLabel.text=@“某些文本”将最大行数设置为0(自动):myLabel.numberOfLines=0将标签的框架设置为最大大小:myLabel.frame=CGRectMake(20,20200800)调用sizeToFit以减小框架大小,使内容刚好适合:[myLabel sizeToFit]
标签框架现在刚好足够高和宽,以适合您的文本。左上角应保持不变。我只测试了左上对齐的文本。对于其他路线,您可能需要随后修改框架。
此外,我的标签启用了换行。
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)
}
}
Swift 2.0版本:
在空Swift文件中生成常量枚举值。
// AppRef.swift
import UIKit
import Foundation
enum UILabelTextPositions : String {
case VERTICAL_ALIGNMENT_TOP = "VerticalAlignmentTop"
case VERTICAL_ALIGNMENT_MIDDLE = "VerticalAlignmentMiddle"
case VERTICAL_ALIGNMENT_BOTTOM = "VerticalAlignmentBottom"
}
使用UILabel扩展:
创建一个空的Swift类并命名它
// AppExtensions.swift
import Foundation
import UIKit
extension UILabel{
func makeLabelTextPosition (sampleLabel :UILabel?, positionIdentifier : String) -> UILabel
{
let rect = sampleLabel!.textRectForBounds(bounds, limitedToNumberOfLines: 0)
switch positionIdentifier
{
case "VerticalAlignmentTop":
sampleLabel!.frame = CGRectMake(bounds.origin.x+5, bounds.origin.y, rect.size.width, rect.size.height)
break;
case "VerticalAlignmentMiddle":
sampleLabel!.frame = CGRectMake(bounds.origin.x+5,bounds.origin.y + (bounds.size.height - rect.size.height) / 2,
rect.size.width, rect.size.height);
break;
case "VerticalAlignmentBottom":
sampleLabel!.frame = CGRectMake(bounds.origin.x+5, bounds.origin.y + (bounds.size.height - rect.size.height),rect.size.width, rect.size.height);
break;
default:
sampleLabel!.frame = bounds;
break;
}
return sampleLabel!
}
}
用法:
myMessageLabel.makeLabelTextPosition(messageLabel, positionIdentifier: UILabelTextPositions.VERTICAL_ALIGNMENT_TOP.rawValue)