core text 這個包默認是沒有的，要自己手動添加進來。
在IOS中利用core text對文本進行排版的幾個關鍵點如下：
字間距：kCTKernAttributeName
行間距：kCTParagraphStyleSpecifierLineSpacingAdjustment 或 kCTParagraphStyleSpecifierLineSpacing(不推薦使用)
段間距：kCTParagraphStyleSpecifierParagraphSpacing
文本對齊方式：kCTParagraphStyleSpecifierAlignment;
還有一點就是core text顯示出來的字是顛倒的，使用時要翻轉下:
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetTextMatrix(context,CGAffineTransformIdentity);
CGContextTranslateCTM(context,0,self.bounds.size.height);
CGContextScaleCTM(context,1.0,-1.0);
最后一點要注意的是Mac下的回車和Windows的是不一樣的，Windows下的回車是由\r \n組成的而Mac下只有一個\n，所以如果沒有去掉的話在每一段的最后都會多出一個空行來，去掉的方法如下：
NSString *myString = [labelString stringByReplacingOccurrencesOfString:"\r\n" withString:"\n"];
具體的代碼實現如下：
#import<Foundation/Foundation.h>
#import<UIKit/UIKit.h>
@interface TextLayoutLabel : UILabel
{
@private
CGFloat characterSpacing_; //字間距
@private
long linesSpacing_; //行間距
}
@property(nonatomic,assign) CGFloat characterSpacing;
@propery(nonatomic,assign)long linesSpacing;
@end
#import "TextLayoutLabel.h"
#import<CoreText/CoreText.h>
@implementation TextLayoutLabel
@synthesize characterSpacing = characterSpacing_;
@synthesize linesSpacing = linesSpacing_;
-(id) initWithFrame:(CGRect)frame
{//初始化字間距、行間距
if(self =[super initWithFrame:frame])
{
self.characterSpacing = 2.0f;
self.linesSpacing = 5.0f;
}
return self;
}
-(void)setCharacterSpacing:(CGFloat)characterSpacing //外部調用設置字間距
{
characterSpacing_ = characterSpacing;
[self setNeedsDisplay];
}
-(void)setLinesSpacing:(long)linesSpacing //外部調用設置行間距
{
linesSpacing_ = linesSpacing;
[self setNeedsDisplay];
}
-(void) drawTextInRect:(CGRect)requestedRect
{
//去掉空行
NSString *labelString = self.text;
NSString *myString = [labelString stringByReplacingOccurrencesOfString:@"\r\n" withString:"\n"];
//創建AttributeString
NSMutableAttributedString *string =[[NSMutableAttributedString alloc]initWithString:self.text];
//設置字體及大小
CTFontRef helveticaBold = CTFontCreateWithName((CFStringRef)self.font.fontName,self.font.pointSize,NULL);
[string addAttribute:(id)kCTFontAttributeName value:(id)helveticaBold range:NSMakeRange(0,[string length])];
//設置字間距
if(self.characterSpacing)
{
long number = self.characterSpacing;
CFNumberRef num = CFNumberCreate(kCFAllocatorDefault,kCFNumberSInt8Type,&number);
[string addAttribute:(id)kCTkernAttributeName value:(id)num rang:NSMakeRange(0,[string length])];
CFRelease(num);
}
//設置字體顏色
[string addAttribute:(id)kCTForegroundColorAttributeName value:(id)(self.textColor.CGColor) range:NSMakeRange(0,[string length])];
//創建文本對齊方式
CTTextAlignment alignment = kCTLeftTextAlignment;
if(self.textAlignment == UITextAlignmentCenter)
{
alignment = kCTCenterTextAlignment;
}
if(self.textAlignment == UITextAlignmentRight)
{
alignment = kCTRightTextAlignment;
}
CTParagraphStyleSetting alignmentStyle;
alignmentStyle.spec = kCTParagraphStyleSpecifierAlignment;
alignmentStyle.valueSize = sizeof(alignment);
alignmentStyle.value = &alignment;
//設置文本行間距
CGFloat lineSpace = self.linesSpacing;
CTParagraphStyleSetting lineSpaceStyle;
lineSpaceStyle.spec = kCTparagraphStyleSpecifierLineSpacingAdjustment;
lineSpaceStyle.valueSize = sizeof(lineSpace);
lineSpaceStyle.value =&lineSpace;
//設置文本段間距
CGFloat paragraphSpacing = 5.0;
CTparagraphStyleSetting paragraphSpaceStyle;
paragraphSpaceStyle.spec = kCTparagraphStyleSpecifierParagraphSpacing;
paragraphSpaceStyle.valueSize = sizeof(CGFloat);
paragraphSpaceStyle.value = ¶graphSpacing;
//創建設置數組
CTParagraphStyleSetting settings[ ] ={alignmentStyle,lineSpaceStyle,paragraphSpaceStyle};
CTParagraphStyleRef style = CTParagraphStyleCreate(settings , sizeof(settings));
//給文本添加設置
[string addAttribute:(id)kCTParagraphStyleAttributeName value:(id)style range:NSMakeRange(0 , [string length])];
//排版
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)string);
CGMutablePathRef leftColumnPath = CGPathCreateMutable();
CGPathAddRect(leftColumnPath, NULL ,CGRectMake(0 , 0 ,self.bounds.size.width , self.bounds.size.height));
CTFrameRef leftFrame = CTFramesetterCreateFrame(framesetter,CFRangeMake(0, 0), leftColumnPath , NULL);
//翻轉坐標系統（文本原來是倒的要翻轉下）
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetTextMatrix(context , CGAffineTransformIdentity);
CGContextTranslateCTM(context , 0 ,self.bounds.size.height);
CGContextScaleCTM(context, 1.0 ,-1.0);
//畫出文本
CTFrameDraw(leftFrame,context);
//釋放
CGPathRelease(leftColumnPath);
CFReleale(framesetter);
CFRelease(helveticaBold);
[string release];
UIGraphicsPushContext(context);
}
@end