CoreText（五）：省略號

直接附代碼：

#import "MyView.h"
#import 

// 行距
const CGFloat kGlobalLineLeading = 5.0;

// 在15字體下，比值小於這個計算出來的高度會導致emoji顯示不全
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 = @"我自橫刀向天笑，去留肝膽兩昆侖。--譚嗣同同學你好啊。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.??????????????去年今日此門中，人面桃花相映紅。人面不知何處去，桃花依舊笑春風。??????????????少年不知愁滋味，愛上層樓，愛上層樓，為賦新詞強說愁。56321363464.而今識盡愁滋味，欲說還休，欲說還休，卻道天涼好個秋。123456，7890，56321267895434。缺月掛疏桐，漏斷人初靜。誰見幽人獨往來，缥缈孤鴻影。驚起卻回頭，有恨無人省。撿盡寒枝不肯棲，寂寞沙洲冷。";
        self.font = [UIFont systemFontOfSize:15];
    }
    return self;
}
/**
 *  高度 = 每行的固定高度 * 行數
 */
+ (CGFloat)textHeightWithText:(NSString *)aText width:(CGFloat)aWidth font:(UIFont *)aFont{
    NSMutableAttributedString *content = [[NSMutableAttributedString alloc] initWithString:aText];
    // 給字符串設置字體行距等樣式
    [self addGlobalAttributeWithContent:content font:aFont];
    CTFramesetterRef framesetterRef = CTFramesetterCreateWithAttributedString((__bridge CFAttributedStringRef)content);
    // 粗略的高度，該高度不准，僅供參考
    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(@"行數 = %ld",lineCount);
    // 總高度 = 行數*每行的高度，其中每行的高度為指定的值，不同字體大小不一樣
    CGFloat accurateHeight = lineCount * (aFont.pointSize * kPerLineRatio);

    CGFloat height = accurateHeight;

    CFRelease(pathRef);
    CFRelease(frameRef);

    return height;
}
#pragma mark - 工具方法
#pragma mark 給字符串添加全局屬性，比如行距，字體大小，默認顏色
+ (void)addGlobalAttributeWithContent:(NSMutableAttributedString *)aContent font:(UIFont *)aFont
{
    CGFloat lineLeading = kGlobalLineLeading; // 行間距

    const CFIndex kNumberOfSettings = 2;
    //設置段落格式
    CTParagraphStyleSetting lineBreakStyle;
    CTLineBreakMode lineBreakMode = kCTLineBreakByWordWrapping;
    lineBreakStyle.spec = kCTParagraphStyleSpecifierLineBreakMode;
    lineBreakStyle.valueSize = sizeof(CTLineBreakMode);
    lineBreakStyle.value = &lineBreakMode;

    //設置行距
    CTParagraphStyleSetting lineSpaceStyle;
    CTParagraphStyleSpecifier spec;
    spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;
    lineSpaceStyle.spec = spec;
    lineSpaceStyle.valueSize = sizeof(CGFloat);
    lineSpaceStyle.value = &lineLeading;

    // 結構體數組
    CTParagraphStyleSetting theSettings[kNumberOfSettings] = {
        lineBreakStyle,
        lineSpaceStyle,
    };
    CTParagraphStyleRef theParagraphRef = CTParagraphStyleCreate(theSettings, kNumberOfSettings);

    // 將設置的行距應用於整段文字
    [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);
    // 將字體大小應用於整段文字
    [aContent addAttribute:NSFontAttributeName value:(__bridge id)fontRef range:NSMakeRange(0, aContent.length)];

    // 給整段文字添加默認顏色
    [aContent addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, aContent.length)];
    // 內存管理
    CFRelease(theParagraphRef);
    CFRelease(fontRef);
}
#pragma mark - 一行一行繪制，行高確定，行與行之間對齊
#pragma mark - 一行一行繪制，行高確定，高度不夠時加上省略號
- (void)drawRectWithLineByLineAlignmentAndEllipses{
    // 1.創建需要繪制的文字
    NSMutableAttributedString *attributed = [[NSMutableAttributedString alloc] initWithString:self.text];

    // 2.設置行距等樣式
    [[self class] addGlobalAttributeWithContent:attributed font:self.font];

    self.textHeight = [[self class] textHeightWithText:self.text width:CGRectGetWidth(self.bounds) font:self.font];

    // 3.創建繪制區域，path的高度對繪制有直接影響，如果高度不夠，則計算出來的CTLine的數量會少一行或者少多行
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), self.textHeight*2));

    // 4.根據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;
    // 繪制全部文本需要的高度大於實際高度則調整，並加上省略號
    if (realHeight > CGRectGetHeight(self.frame)){
        realHeight = CGRectGetHeight(self.frame);
    }
    NSLog(@"realHeight = %f",realHeight);
    // 獲取上下文
    CGContextRef contextRef = UIGraphicsGetCurrentContext();

    // 轉換坐標系
    CGContextSetTextMatrix(contextRef, CGAffineTransformIdentity);
    CGContextTranslateCTM(contextRef, 0, realHeight); // 這裡跟著調整
    CGContextScaleCTM(contextRef, 1.0, -1.0);

    // 這裡可調整可不調整
    CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), realHeight));

    // 一行一行繪制
    CFArrayRef lines = CTFrameGetLines(ctFrame);
    CFIndex lineCount = CFArrayGetCount(lines);
    CGPoint lineOrigins[lineCount];
    // 把ctFrame裡每一行的初始坐標寫到數組裡，注意CoreText的坐標是左下角為原點
    CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), lineOrigins);
    CGFloat frameY = 0;
    for (CFIndex i = 0; i < lineCount; i++){
        // 遍歷每一行CTLine
        CTLineRef line = CFArrayGetValueAtIndex(lines, i);
        CGFloat lineAscent;
        CGFloat lineDescent;
        CGFloat lineLeading; // 行距
        // 該函數除了會設置好ascent,descent,leading之外，還會返回這行的寬度
        CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, &lineLeading);
        //CoreText的origin的Y值是在baseLine處，而不是下方的descent。
        CGPoint lineOrigin = lineOrigins[i];
        //行高
        CGFloat lineHeight = self.font.pointSize * kPerLineRatio;
        //self.font.descender為負值
        frameY = realHeight - (i + 1)*lineHeight - self.font.descender;
        NSLog(@"frameY = %f",frameY);
        lineOrigin.y = frameY;
        //調整坐標
        CGContextSetTextPosition(contextRef, lineOrigin.x, lineOrigin.y);
        if (frameY + self.font.descender > lineHeight){
            CTLineDraw(line, contextRef);
        }else{
            NSLog(@"最後一行");
            // 最後一行，加上省略號
            static NSString* const kEllipsesCharacter = @"\u2026";
            CFRange lastLineRange = CTLineGetStringRange(line);
            // 一個emoji表情占用兩個長度單位
            NSLog(@"range.location = %ld,range.length = %ld,總長度 = %ld",lastLineRange.location,lastLineRange.length,attributed.length);
            if (lastLineRange.location + lastLineRange.length < (CFIndex)attributed.length){
                // 這一行放不下所有的字符（下一行還有字符），則把此行後面的回車、空格符去掉後，再把最後一個字符替換成省略號
                CTLineTruncationType truncationType = kCTLineTruncationEnd;
                NSUInteger truncationAttributePosition = lastLineRange.location + lastLineRange.length - 1;

                // 拿到最後一個字符的屬性字典
                NSDictionary *tokenAttributes = [attributed attributesAtIndex:truncationAttributePosition
                                                               effectiveRange:NULL];
                // 給省略號字符設置字體大小、顏色等屬性
                NSAttributedString *tokenString = [[NSAttributedString alloc] initWithString:kEllipsesCharacter
                                                                                  attributes:tokenAttributes];

                // 用省略號單獨創建一個CTLine，下面在截斷重新生成CTLine的時候會用到
                CTLineRef truncationToken = CTLineCreateWithAttributedString((__bridge CFAttributedStringRef)tokenString);

                // 把這一行的屬性字符串復制一份，如果要把省略號放到中間或其他位置，只需指定復制的長度即可
                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];

                    // 如果復制字符串的最後一個字符是換行、空格符，則刪掉
                    if ([[NSCharacterSet whitespaceAndNewlineCharacterSet] characterIsMember:lastCharacter])
                    {
                        [truncationString deleteCharactersInRange:NSMakeRange(copyLength - 1, 1)];
                    }
                }

                // 拼接省略號到復制字符串的最後
                [truncationString appendAttributedString:tokenString];

                // 把新的字符串創建成CTLine
                CTLineRef truncationLine = CTLineCreateWithAttributedString((__bridge CFAttributedStringRef)truncationString);

                // 創建一個截斷的CTLine，該方法不能少，具體作用還有待研究
                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{
                // 這一行剛好是最後一行，且最後一行的字符可以完全繪制出來
                CTLineDraw(line, contextRef);
            }
            // 跳出循環，避免繪制剩下的多余的CTLine
            break;
        }
    }
    CFRelease(path);
    CFRelease(framesetter);
    CFRelease(ctFrame);
}



- (void)drawRect:(CGRect)rect
{
    [self drawRectWithLineByLineAlignmentAndEllipses];
}
@end

調用：

- (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 = @"我自橫刀向天笑，去留肝膽兩昆侖。--譚嗣同同學你好啊。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.??????????????去年今日此門中，人面桃花相映紅。人面不知何處去，桃花依舊笑春風。??????????????少年不知愁滋味，愛上層樓，愛上層樓，為賦新詞強說愁。56321363464.而今識盡愁滋味，欲說還休，欲說還休，卻道天涼好個秋。123456，7890，56321267895434。缺月掛疏桐，漏斷人初靜。誰見幽人獨往來，缥缈孤鴻影。驚起卻回頭，有恨無人省。撿盡寒枝不肯棲，寂寞沙洲冷。";
    view.font = [UIFont systemFontOfSize:15];
    [self.view addSubview:view];
}

結果：