直接附代码：
#import "MyView.h"
#import <CoreText/CoreText.h>
// 行距
const CGFloat kGlobalLineLeading = 5.0;
// 在15字体下，比值小于这个计算出来的高度会导致emoji显示不全
const CGFloat kPerLineRatio = 1.4;
@interface MyView()
@property (nonatomic ,assign) CGFloat textHeight;
@end
@implementation MyView
- (instancetype)initWithFrame:(CGRect)frame{
self = [super initWithFrame:frame];
if (self) {
self.text = @"我自横刀向天笑，去留肝胆两昆仑。--谭嗣同同学你好啊。This is my first CoreText demo,how are you ?I love three things,the sun,the moon,and you.the sun for the day,the moon for the night,and you forever.��������������去年今日此门中，人面桃花相映红。人面不知何处去，桃花依旧笑春风。��������������少年不知愁滋味，爱上层楼，爱上层楼，为赋新词强说愁。56321363464.而今识尽愁滋味，欲说还休，欲说还休，却道天凉好个秋。123456，7890，56321267895434。缺月挂疏桐，漏断人初静。谁见幽人独往来，缥缈孤鸿影。惊起却回头，有恨无人省。捡尽寒枝不肯栖，寂寞沙洲冷。";
self.font = [UIFont systemFontOfSize:15];
}
return self;
}
/**
* 高度 = 每行的固定高度 * 行数
*/
+ (CGFloat)textHeightWithText:(NSString *)aText width:(CGFloat)aWidth font:(UIFont *)aFont{
NSMutableAttributedString *content = [[NSMutableAttributedString alloc] initWithString:aText];
// 给字符串设置字体行距等样式
[self addGlobalAttributeWithContent:content font:aFont];
CTFramesetterRef framesetterRef = CTFramesetterCreateWithAttributedString((__bridge CFAttributedStringRef)content);
// 粗略的高度，该高度不准，仅供参考
CGSize suggestSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetterRef, CFRangeMake(0, content.length), NULL, CGSizeMake(aWidth, MAXFLOAT), NULL);
NSLog(@"suggestHeight = %f",suggestSize.height);
CGMutablePathRef pathRef = CGPathCreateMutable();
CGPathAddRect(pathRef, NULL, CGRectMake(0, 0, aWidth, suggestSize.height));
CTFrameRef frameRef = CTFramesetterCreateFrame(framesetterRef, CFRangeMake(0, content.length), pathRef, NULL);
CFArrayRef lines = CTFrameGetLines(frameRef);
CFIndex lineCount = CFArrayGetCount(lines);
NSLog(@"行数 = %ld",lineCount);
// 总高度 = 行数*每行的高度，其中每行的高度为指定的值，不同字体大小不一样
CGFloat accurateHeight = lineCount * (aFont.pointSize * kPerLineRatio);
CGFloat height = accurateHeight;
CFRelease(pathRef);
CFRelease(frameRef);
return height;
}
#pragma mark - 工具方法
#pragma mark 给字符串添加全局属性，比如行距，字体大小，默认颜色
+ (void)addGlobalAttributeWithContent:(NSMutableAttributedString *)aContent font:(UIFont *)aFont
{
CGFloat lineLeading = kGlobalLineLeading; // 行间距
const CFIndex kNumberOfSettings = 2;
//设置段落格式
CTParagraphStyleSetting lineBreakStyle;
CTLineBreakMode lineBreakMode = kCTLineBreakByWordWrapping;
lineBreakStyle.spec = kCTParagraphStyleSpecifierLineBreakMode;
lineBreakStyle.valueSize = sizeof(CTLineBreakMode);
lineBreakStyle.value = &lineBreakMode;
//设置行距
CTParagraphStyleSetting lineSpaceStyle;
CTParagraphStyleSpecifier spec;
spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;
lineSpaceStyle.spec = spec;
lineSpaceStyle.valueSize = sizeof(CGFloat);
lineSpaceStyle.value = &lineLeading;
// 结构体数组
CTParagraphStyleSetting theSettings[kNumberOfSettings] = {
lineBreakStyle,
lineSpaceStyle,
};
CTParagraphStyleRef theParagraphRef = CTParagraphStyleCreate(theSettings, kNumberOfSettings);
// 将设置的行距应用于整段文字
[aContent addAttribute:NSParagraphStyleAttributeName value:(__bridge id)(theParagraphRef) range:NSMakeRange(0, aContent.length)];
CFStringRef fontName = (__bridge CFStringRef)aFont.fontName;
CTFontRef fontRef = CTFontCreateWithName(fontName, aFont.pointSize, NULL);
// 将字体大小应用于整段文字
[aContent addAttribute:NSFontAttributeName value:(__bridge id)fontRef range:NSMakeRange(0, aContent.length)];
// 给整段文字添加默认颜色
[aContent addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, aContent.length)];
// 内存管理
CFRelease(theParagraphRef);
CFRelease(fontRef);
}
#pragma mark - 一行一行绘制，行高确定，行与行之间对齐
#pragma mark - 一行一行绘制，行高确定，高度不够时加上省略号
- (void)drawRectWithLineByLineAlignmentAndEllipses{
// 1.创建需要绘制的文字
NSMutableAttributedString *attributed = [[NSMutableAttributedString alloc] initWithString:self.text];
// 2.设置行距等样式
[[self class] addGlobalAttributeWithContent:attributed font:self.font];
self.textHeight = [[self class] textHeightWithText:self.text width:CGRectGetWidth(self.bounds) font:self.font];
// 3.创建绘制区域，path的高度对绘制有直接影响，如果高度不够，则计算出来的CTLine的数量会少一行或者少多行
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), self.textHeight*2));
// 4.根据NSAttributedString生成CTFramesetterRef
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributed);
CTFrameRef ctFrame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, attributed.length), path, NULL);
// 重置高度
CGFloat realHeight = self.textHeight;
// 绘制全部文本需要的高度大于实际高度则调整，并加上省略号
if (realHeight > CGRectGetHeight(self.frame)){
realHeight = CGRectGetHeight(self.frame);
}
NSLog(@"realHeight = %f",realHeight);
// 获取上下文
CGContextRef contextRef = UIGraphicsGetCurrentContext();
// 转换坐标系
CGContextSetTextMatrix(contextRef, CGAffineTransformIdentity);
CGContextTranslateCTM(contextRef, 0, realHeight); // 这里跟着调整
CGContextScaleCTM(contextRef, 1.0, -1.0);
// 这里可调整可不调整
CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), realHeight));
// 一行一行绘制
CFArrayRef lines = CTFrameGetLines(ctFrame);
CFIndex lineCount = CFArrayGetCount(lines);
CGPoint lineOrigins[lineCount];
// 把ctFrame里每一行的初始坐标写到数组里，注意CoreText的坐标是左下角为原点
CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), lineOrigins);
CGFloat frameY = 0;
for (CFIndex i = 0; i < lineCount; i++){
// 遍历每一行CTLine
CTLineRef line = CFArrayGetValueAtIndex(lines, i);
CGFloat lineAscent;
CGFloat lineDescent;
CGFloat lineLeading; // 行距
// 该函数除了会设置好ascent,descent,leading之外，还会返回这行的宽度
CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, &lineLeading);
//CoreText的origin的Y值是在baseLine处，而不是下方的descent。
CGPoint lineOrigin = lineOrigins[i];
//行高
CGFloat lineHeight = self.font.pointSize * kPerLineRatio;
//self.font.descender为负值
frameY = realHeight - (i + 1)*lineHeight - self.font.descender;
NSLog(@"frameY = %f",frameY);
lineOrigin.y = frameY;
//调整坐标
CGContextSetTextPosition(contextRef, lineOrigin.x, lineOrigin.y);
if (frameY + self.font.descender > lineHeight){
CTLineDraw(line, contextRef);
}else{
NSLog(@"最后一行");
// 最后一行，加上省略号
static NSString* const kEllipsesCharacter = @"\u2026";
CFRange lastLineRange = CTLineGetStringRange(line);
// 一个emoji表情占用两个长度单位
NSLog(@"range.location = %ld,range.length = %ld,总长度 = %ld",lastLineRange.location,lastLineRange.length,attributed.length);
if (lastLineRange.location + lastLineRange.length < (CFIndex)attributed.length){
// 这一行放不下所有的字符（下一行还有字符），则把此行后面的回车、空格符去掉后，再把最后一个字符替换成省略号
CTLineTruncationType truncationType = kCTLineTruncationEnd;
NSUInteger truncationAttributePosition = lastLineRange.location + lastLineRange.length - 1;
// 拿到最后一个字符的属性字典
NSDictionary *tokenAttributes = [attributed attributesAtIndex:truncationAttributePosition
effectiveRange:NULL];
// 给省略号字符设置字体大小、颜色等属性
NSAttributedString *tokenString = [[NSAttributedString alloc] initWithString:kEllipsesCharacter
attributes:tokenAttributes];
// 用省略号单独创建一个CTLine，下面在截断重新生成CTLine的时候会用到
CTLineRef truncationToken = CTLineCreateWithAttributedString((__bridge CFAttributedStringRef)tokenString);
// 把这一行的属性字符串复制一份，如果要把省略号放到中间或其他位置，只需指定复制的长度即可
NSUInteger copyLength = lastLineRange.length;
NSMutableAttributedString *truncationString = [[attributed attributedSubstringFromRange:NSMakeRange(lastLineRange.location, copyLength)] mutableCopy];
if (lastLineRange.length > 0)
{
// Remove any whitespace at the end of the line.
unichar lastCharacter = [[truncationString string] characterAtIndex:copyLength - 1];
// 如果复制字符串的最后一个字符是换行、空格符，则删掉
if ([[NSCharacterSet whitespaceAndNewlineCharacterSet] characterIsMember:lastCharacter])
{
[truncationString deleteCharactersInRange:NSMakeRange(copyLength - 1, 1)];
}
}
// 拼接省略号到复制字符串的最后
[truncationString appendAttributedString:tokenString];
// 把新的字符串创建成CTLine
CTLineRef truncationLine = CTLineCreateWithAttributedString((__bridge CFAttributedStringRef)truncationString);
// 创建一个截断的CTLine，该方法不能少，具体作用还有待研究
CTLineRef truncatedLine = CTLineCreateTruncatedLine(truncationLine, self.frame.size.width, truncationType, truncationToken);
if (!truncatedLine)
{
// If the line is not as wide as the truncationToken, truncatedLine is NULL
truncatedLine = CFRetain(truncationToken);
}
CFRelease(truncationLine);
CFRelease(truncationToken);
CTLineDraw(truncatedLine, contextRef);
CFRelease(truncatedLine);
} else{
// 这一行刚好是最后一行，且最后一行的字符可以完全绘制出来
CTLineDraw(line, contextRef);
}
// 跳出循环，避免绘制剩下的多余的CTLine
break;
}
}
CFRelease(path);
CFRelease(framesetter);
CFRelease(ctFrame);
}
- (void)drawRect:(CGRect)rect
{
[self drawRectWithLineByLineAlignmentAndEllipses];
}
@end调用：
- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor whiteColor];
// Do any additional setup after loading the view, typically from a nib.
MyView *view = [[MyView alloc]initWithFrame:CGRectMake(0, 20, self.view.width, 100)];
view.backgroundColor = [UIColor redColor];
view.text = @"我自横刀向天笑，去留肝胆两昆仑。--谭嗣同同学你好啊。This is my first CoreText demo,how are you ?I love three things,the sun,the moon,and you.the sun for the day,the moon for the night,and you forever.��������������去年今日此门中，人面桃花相映红。人面不知何处去，桃花依旧笑春风。��������������少年不知愁滋味，爱上层楼，爱上层楼，为赋新词强说愁。56321363464.而今识尽愁滋味，欲说还休，欲说还休，却道天凉好个秋。123456，7890，56321267895434。缺月挂疏桐，漏断人初静。谁见幽人独往来，缥缈孤鸿影。惊起却回头，有恨无人省。捡尽寒枝不肯栖，寂寞沙洲冷。";
view.font = [UIFont systemFontOfSize:15];
[self.view addSubview:view];
}结果：
参考：
CoreText使用教程(四)
作者：xiaoxiaobukuang 发表于2016/9/19 16:41:55 原文链接
阅读：141 评论：0 查看评论