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CoreText（五）：省略号

来源：程序员人生发布时间：2016-12-08 17:10:01 阅读次数：2478次

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致使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.��������������去年本日此门中，人面桃花相映红。人面不知何处去，桃花照旧笑春风。��������������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。谁见幽人独来往，缥缈孤鸿影。惊起却回头，有恨无人省。捡尽寒枝不肯栖，孤单沙洲冷。";
        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1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，默许色彩
+ (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);

    // 将设置的行距利用于整段文字
    [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);
    // 将字体大小利用于整段文字
    [aContent addAttribute:NSFontAttributeName value:(__bridge id)fontRef range:NSMakeRange(0, aContent.length)];

    // 给整段文字添加默许色彩
    [aContent addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, aContent.length)];
    // 内存管理
    CFRelease(theParagraphRef);
    CFRelease(fontRef);
}
#pragma mark - 1行1行绘制，行高肯定，行与行之间对齐
#pragma mark - 1行1行绘制，行高肯定，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1行或少多行
    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剂，并加上省略号
    if (realHeight > CGRectGetHeight(self.frame)){
        realHeight = CGRectGetHeight(self.frame);
    }
    NSLog(@"realHeight = %f",realHeight);
    // 获得上下文
    CGContextRef contextRef = UIGraphicsGetCurrentContext();

    // 转换坐标系
    CGContextSetTextMatrix(contextRef, CGAffineTransformIdentity);
    CGContextTranslateCTM(contextRef, 0, realHeight); // 这里随着调剂
    CGContextScaleCTM(contextRef, 1.0, -1.0);

    // 这里可调剂可不调剂
    CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), realHeight));

    // 1行1行绘制
    CFArrayRef lines = CTFrameGetLines(ctFrame);
    CFIndex lineCount = CFArrayGetCount(lines);
    CGPoint lineOrigins[lineCount];
    // 把ctFrame里每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++){
        // 遍历每行CTLine
        CTLineRef line = CFArrayGetValueAtIndex(lines, i);
        CGFloat lineAscent;
        CGFloat lineDescent;
        CGFloat lineLeading; // 行距
        // 该函数除会设置好ascent,descent,leading以外，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;
        //调剂坐标
        CGContextSetTextPosition(contextRef, lineOrigin.x, lineOrigin.y);
        if (frameY + self.font.descender > lineHeight){
            CTLineDraw(line, contextRef);
        }else{
            NSLog(@"最后1行");
            // 最后1行，加上省略号
            static NSString* const kEllipsesCharacter = @"\u2026";
            CFRange lastLineRange = CTLineGetStringRange(line);
            // 1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1行放不下所有的字符（下1行还有字符），则把此行后面的回车、空格符去掉后，再把最后1个字符替换成省略号
                CTLineTruncationType truncationType = kCTLineTruncationEnd;
                NSUInteger truncationAttributePosition = lastLineRange.location + lastLineRange.length - 1;

                // 拿到最后1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、色彩等属性
                NSAttributedString *tokenString = [[NSAttributedString alloc] initWithString:kEllipsesCharacter
                                                                                  attributes:tokenAttributes];

                // 用省略号单独创建1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1行的属性字符串复制1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便可
                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1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1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1行恰好是最后1行，且最后1行的字符可以完全绘制出来
                CTLineDraw(line, contextRef);
            }
            // 跳出循环，避免绘制剩下的过剩的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.��������������去年本日此门中，人面桃花相映红。人面不知何处去，桃花照旧笑春风。��������������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。谁见幽人独来往，缥缈孤鸿影。惊起却回头，有恨无人省。捡尽寒枝不肯栖，孤单沙洲冷。";
    view.font = [UIFont systemFontOfSize:15];
    [self.view addSubview:view];
}

结果：
这里写图片描述

参考：
CoreText使用教程(4)

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