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
就像上面的答案一样,但它不太正确,或者很容易插入代码,所以我稍微清理了一下。将此扩展名添加到它自己的.h和.m文件中,或者直接粘贴到您打算使用的实现上方:
#pragma mark VerticalAlign
@interface UILabel (VerticalAlign)
- (void)alignTop;
- (void)alignBottom;
@end
@implementation UILabel (VerticalAlign)
- (void)alignTop
{
CGSize fontSize = [self.text sizeWithFont:self.font];
double finalHeight = fontSize.height * self.numberOfLines;
double finalWidth = self.frame.size.width; //expected width of label
CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
int newLinesToPad = (finalHeight - theStringSize.height) / fontSize.height;
for(int i=0; i<= newLinesToPad; i++)
{
self.text = [self.text stringByAppendingString:@" \n"];
}
}
- (void)alignBottom
{
CGSize fontSize = [self.text sizeWithFont:self.font];
double finalHeight = fontSize.height * self.numberOfLines;
double finalWidth = self.frame.size.width; //expected width of label
CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
int newLinesToPad = (finalHeight - theStringSize.height) / fontSize.height;
for(int i=0; i< newLinesToPad; i++)
{
self.text = [NSString stringWithFormat:@" \n%@",self.text];
}
}
@end
然后要使用,请将文本放入标签中,然后调用适当的方法将其对齐:
[myLabel alignTop];
or
[myLabel alignBottom];
其他回答
我在应用程序中所做的是将UILabel的line属性设置为0,并创建UILabel的底部约束,并确保其设置为>=0,如下图所示。
您可以使用TTTAttributedLabel,它支持垂直对齐。
@property (nonatomic) TTTAttributedLabel* label;
<...>
//view's or viewController's init method
_label.verticalAlignment = TTTAttributedLabelVerticalAlignmentTop;
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
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。
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