UILabel算是iOS里使用最多的控件了吧，下面来说说它特殊的应用需求吧

一、设置字间距、行间距

这是一个比较常见的需求了

写一个UILabel的分类

@interface UILabel (extension)

/**

* 设置字间距

*/

-(void)setColumnSpace:(CGFloat)columnSpace;

/**

* 设置行距

*/

- (void)setRowSpace:(CGFloat)rowSpace;

@end

#import "UILabel+extension.h"

#import

@implementation UILabel (extension)

- (void)setColumnSpace:(CGFloat)columnSpace

{

NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithAttributedString:self.attributedText];

//调整间距

[attributedString addAttribute:(__bridge NSString *)kCTKernAttributeName value:@(columnSpace) range:NSMakeRange(0, [attributedString length])];

self.attributedText = attributedString;

}

- (void)setRowSpace:(CGFloat)rowSpace

{

self.numberOfLines = 0;

NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithAttributedString:self.attributedText];

//调整行距

NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];

paragraphStyle.lineSpacing = rowSpace;

paragraphStyle.baseWritingDirection = NSWritingDirectionLeftToRight;

[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [self.text length])];

self.attributedText = attributedString;

}

@end

然后再重写UILabel

@interface RDNewLabel : UILabel

@property (nonatomic, assign) float charactSpace; //字间距

@property (nonatomic, assign) float lineSpace; //行间距

+ (CGFloat)textHeight:(NSString *)text width:(CGFloat)labelWidth font:(UIFont *)font charactSpace:(CGFloat)charactSpace LineSpace:(CGFloat)lineSpace numberLines:(NSInteger)numberLines;

(CGFloat)textWidth:(NSString *)text height:(CGFloat)labelHeight font:(UIFont *)font charactSpace:(CGFloat)charactSpace LineSpace:(CGFloat)lineSpace;

#define CharactSpacing 0.4 //字间距

#define LinesSpacing 4.0 //行间距

@implementation RDNewLabel

- (void)setText:(NSString *)text{

[super setText:text];

//默认字间距为0.4

if (_charactSpace==0) {

[self setColumnSpace:CharactSpacing];

}else{

[self setColumnSpace:_charactSpace];

}

//默认行间距为4.0，当设置0.01时则不设置行间距

if (_lineSpace == 0) {

[self setRowSpace:LinesSpacing];

}else{

if (_lineSpace <= 0.01) {

}else{

[self setRowSpace:_lineSpace];

}

}

}

+ (CGFloat)textHeight:(NSString *)text width:(CGFloat)labelWidth font:(UIFont *)font charactSpace:(CGFloat)charactSpace LineSpace:(CGFloat)lineSpace numberLines:(NSInteger)numberLines{

CGFloat textHeight = 0;

RDNewLabel *label = [RDNewLabel new];

label.font = font;

if (charactSpace == 0) {

charactSpace = CharactSpacing;

}

label.charactSpace = charactSpace;

if (lineSpace == 0) {

lineSpace = LinesSpacing;

}

label.lineSpace = lineSpace;

label.text = text;

label.numberOfLines = numberLines;

textHeight = [label sizeThatFits:CGSizeMake(labelWidth, MAXFLOAT)].height;

return textHeight;

}

+ (CGFloat)textWidth:(NSString *)text height:(CGFloat)labelHeight font:(UIFont *)font charactSpace:(CGFloat)charactSpace LineSpace:(CGFloat)lineSpace{

CGFloat textWidth = 0;

RDNewLabel *label = [RDNewLabel new];

label.font = font;

if (charactSpace == 0) {

charactSpace = CharactSpacing;

}

label.charactSpace = charactSpace;

if (lineSpace == 0) {

lineSpace = LinesSpacing;

}

label.lineSpace = lineSpace;

label.text = text;

label.numberOfLines = 0;

textWidth = [label sizeThatFits:CGSizeMake(MAXFLOAT, labelHeight)].width;

return textWidth;

}

二、Label 两端对齐

很多情况我们会遇到这样的需求，要求Label文字两端对齐。

使用UILabel的NSTextAlignment设置两端对齐并不是达到效果，而使用UILabel的attributedText确实可以实现两端对齐。

重写UILabel的setText方法

@implementation ALLabel

- (void)setText:(NSString *)text{

NSMutableAttributedString *attributedStr = [[NSMutableAttributedString alloc]initWithString:text];

NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc]init];

paragraphStyle.alignment = NSTextAlignmentJustified;//设置两端对齐

[attributedStr setAttributes:@{NSParagraphStyleAttributeName:paragraphStyle,NSFontAttributeName:self.font,NSUnderlineStyleAttributeName:[NSNumber numberWithInteger:NSUnderlineStyleNone]} range:NSMakeRange(0, attributedStr.length)];

[self setAttributedText:attributedStr];

}

初始化一个ALLabel

@property (weak, nonatomic) IBOutlet ALLabel *label;

NSString* msg = @"壬戌之秋，七月既望，苏子与客泛舟游于赤壁之下。清风《赤壁赋》文徵明书徐来，水波不兴。举酒属(zhǔ)客，诵明月之诗，歌窈窕之章。少(shǎo) 焉，月出于东山之上，徘徊于斗(dǒu)牛之间。白露横江，水光接天。纵一苇之所如，凌万顷之茫然。浩浩乎如冯 (píng) 虚御风，而不知其所止；飘飘乎如遗世独立，羽化而登仙。”

_label.text = msg;

计算label自适应高度还是一样

CGSize resultSize = [msg boundingRectWithSize:size options:NSStringDrawingTruncatesLastVisibleLine | NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: [UIFont systemFontOfSize:fontSize]} context:nil].size

三、分行显示

也许我们会遇到类似需求：本来多行的文字，却首先只显示两行，最二行末尾处放置一个“查看更多”的按钮，点击查看更多按钮则全部显示。

思路：

1、设置一个lines为0的allTextLabel；

2、放置一个lines为1的firstLineLabel，top、left、right和allTextLabel对齐；

3、放置一个lines也为1的secondLineLabel，left与firstLineLabel对齐，top与firstLineLabel的bottom间距为0，right与“查看更多按钮”的间距为0；

4、放置一个“查看更多”的按钮moreTextButton，right与firstLineLabel对齐，top与firstLineLabel的bottom间距为0，宽度固定

@property (weak, nonatomic) IBOutlet UILabel *allTextLabel;

@property (weak, nonatomic) IBOutlet UILabel *firstLineLabel;

@property (weak, nonatomic) IBOutlet UILabel *secondLineLabel;

@property (weak, nonatomic) IBOutlet UIButton *moreTextButton;

根据文字内容和宽度返回一个以行数line为索引的数组

#import

- (NSArray *)getSeparatedLinesFromLabelText:(NSString *)text font:(UIFont *)font width:(CGFloat)width

{

CTFontRef myFont = CTFontCreateWithName((__bridge CFStringRef)([font fontName]), [font pointSize], NULL);

NSMutableAttributedString *attStr = [[NSMutableAttributedString alloc] initWithString:text];

[attStr addAttribute:(NSString *)kCTFontAttributeName value:(__bridge id)myFont range:NSMakeRange(0, attStr.length)];

CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((__bridge CFAttributedStringRef)attStr);

CGMutablePathRef path = CGPathCreateMutable();

CGPathAddRect(path, NULL, CGRectMake(0,0,width,MAXFLOAT));

CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL);

NSArray *lines = (__bridge NSArray *)CTFrameGetLines(frame);

NSMutableArray *linesArray = [[NSMutableArray alloc]init];

for (id line in lines)

{

CTLineRef lineRef = (__bridge CTLineRef )line;

CFRange lineRange = CTLineGetStringRange(lineRef);

NSRange range = NSMakeRange(lineRange.location, lineRange.length);

NSString *lineString = [text substringWithRange:range];

[linesArray addObject:lineString];

}

return linesArray;

}

接下来就是赋值了

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view.

NSString * msg = @"土地是以它的肥沃和收获而被估价的；才能也是土地，不过它生产的不是粮食，而是真理。如果只能滋生瞑想和幻想的话，即使再大的才能也只是砂地或盐池，那上面连小草也长不出来的

_allTextLabel.hidden = TRUE;

CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width;

_textLines = [self getSeparatedLinesFromLabelText:msg font:[UIFont systemFontOfSize:15] width:screenWidth-90];

_firstLineLabel.text = _textLines[0];

_secondLineLabel.text = _textLines[1];

}

点击查看更多按钮，其实就是赋值后隐藏firstLineLabel和secondLineLabel

- (IBAction)onClickShowMoreText:(id)sender {

_allTextLabel.text = msg ;

_allTextLabel.hidden = FALSE;

_firstLineLabel.hidden = TRUE;

_secondLineLabel.hidden = TRUE;

_moreTextButton.hidden = TRUE;

}