iOS CoreText類庫的詳細介紹

iOS 編程中如何使用CoreText類庫

從框架圖中我們可以看出：

CTFrame 作爲一個整體的畫布(Canvas)，其中由行(CTLine)組成，而每行可以分爲一個或多個小方塊（CTRun）。

注意：你不需要自己創建CTRun，Core Text將根據NSAttributedString的屬性來自動創建CTRun。每個CTRun對象對應不同的屬性，正因此，你可以自由的控制字體、顏色、字間距等等信息。

通常處理步聚：

1.使用core text就是先有一個要顯示的string，然後定義這個string每個部分的樣式－>attributedString －> 生成 CTFramesetter -> 得到CTFrame -> 繪製（CTFrameDraw）
其中可以更詳細的設置換行方式，對齊方式，繪製區域的大小等。
2.繪製只是顯示，點擊事件就需要一個判斷了。
CTFrame 包含了多個CTLine,並且可以得到各個line的其實位置與大小。判斷點擊處在不在某個line上。CTLine 又可以判斷這個點(相對於ctline的座標)處的文字範圍。然後遍歷這個string的所有NSTextCheckingResult，根據result的rang判斷點擊處在不在這個rang上，從而得到點擊的鏈接與位置。

首先，創建工程，添加系統庫CoreText

//
//  CoreTextView.m
//  CoreTextDemo
//
//  Created by swplzj on 13-10-30.
//  Copyright (c) 2013年 swplzj. All rights reserved.
//

#import "CoreTextView.h"
#import <CoreText/CoreText.h>
#import <math.h>

@implementation CoreTextView

static inline double radians (double degrees)
{
    return degrees * M_PI / 180;
}

void ctLineAndRun(CTFrameRef frame)
{
    int lineIndex = 1;
    //獲取frame中的所有行
    CFArrayRef allLines = CTFrameGetLines(frame);
    //獲取frame中第一行的元素
    CTLineRef firstLineRef = CFArrayGetValueAtIndex(allLines, lineIndex);
    //獲得frame中所有的行數
    int linesCount = CFArrayGetCount(allLines);
    NSLog(@"ctLine的總數量：%d", linesCount);
    //獲取frame中的所有CTRun
    CFArrayRef ctRun = CTLineGetGlyphRuns(firstLineRef);
//    CTRunRef firstRun = CFArrayGetValueAtIndex(ctRun, 0);
//    int runsNum = CTLineGetGlyphCount(ctRun);
    NSLog(@"ctRun的數量：%ld", CFArrayGetCount(ctRun));

    //按長度截斷字符串：省略號
    NSAttributedString *attributedStr = [[NSAttributedString alloc] initWithString:@"\u2026"];
    CTLineRef lineToken = CTLineCreateWithAttributedString((CFAttributedStringRef) attributedStr);
    //截斷的方式
    CTLineTruncationType lineTruncationType = kCTLineTruncationEnd;
    CTLineRef newLine = CTLineCreateTruncatedLine(firstLineRef, 260, lineTruncationType, lineToken);
    CGContextRef context = UIGraphicsGetCurrentContext();
    //重置畫布
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    //保存Context狀態
    CGContextSaveGState(context);
    
    CGMutablePathRef path = CGPathCreateMutable();
    CGRect bounds = CGRectInset((CGRect) {{40, 40}, {320 - 80, 40}}, 0.0f, 0.0f);
    CGPathAddRect(path, NULL, bounds);
    CGContextAddPath(context, path);
    CGContextSetFillColorWithColor(context, [UIColor orangeColor].CGColor);
    CGContextFillPath(context);
    CGContextSetTextPosition(context, 40, 40);
    CTLineDraw(newLine, context);
    CGPathCloseSubpath(path);
    CGPathRelease(path);

    //獲取一行文字中，指定charIndex字符(也就是StringRange的Location)相對ctline本身x原點的偏移量（譬如第一個字符很顯然是0），返回值與secondaryOffset同爲一個值,另外也可以用來求一行字符所佔的像素長度
    //第二個字符index位置是在ctframe整個中的位置，譬如第二行的第一個字符的index是加上第一行所有字符後的index
    CGFloat secondaryOffSet;
    CGFloat primaryOffSet = CTLineGetOffsetForStringIndex(firstLineRef, CTLineGetStringRange(firstLineRef).location, &secondaryOffSet);
    NSLog(@"第%ld個字符與本身x原點的偏移量:%f",CTLineGetStringRange(firstLineRef).location + 1,primaryOffSet);
    
    //獲取相對於Flush的偏移量
    //    CGFloat penOffset = CTLineGetPenOffsetForFlush(firstLine, NSTextAlignmentLeft, 240);
    //    NSLog(@"相對於Flush的偏移量:%f",penOffset);
    
    //CTLineGetStringIndexForPosition 這個方法主要是獲得某個ctline中某個位置（position）的character在整個ctframe中的index.這個方法在當有段前縮進或者首行縮進的時候，並不準確，不會跟着縮進而進行偏移，所以段前縮進多少，就需要把position的x值減去多少（譬如段前縮進是20，則要減去20個單位），所以，這個方法最好的用處就是判斷一行ctline最多容納多少的字符，只需把這個point的x位置調很大（超過ctframe path的寬度）就可以了。
    CGPoint origins[linesCount];
    CTFrameGetLineOrigins(frame,CFRangeMake(0, 0), origins);
    CGPoint indexPoint = origins[lineIndex];
    indexPoint.x -= 20;//段前縮進20,需要減去20//indexPoint.x += 300;可以求
    CFIndex index = CTLineGetStringIndexForPosition(firstLineRef, indexPoint);
    NSLog(@"ctframe中%@位置（position）的字符索引:%ld",NSStringFromCGPoint(indexPoint),index);
    
    //CTLine在整個文本中所處的range，location是該行前面n行的字符數和，換行符也包括
    //    CFRange range = CTLineGetStringRange(firstLine);
    //    NSLog(@"location:%ld=====length:%ld",range.location,range.length);
    
    //獲取一行中上行高(ascent)，下行高(descent)，行距(leading),整行高爲(ascent+|descent|+leading) 返回值爲整行字符串長度佔有的像素寬度。
    //    CGFloat asc,des,lead;
    //    double lineWidth = CTLineGetTypographicBounds(firstLine, &asc, &des, &lead);
    //    NSLog(@"ascent = %f,descent = %f,leading = %f,lineWidth = %f",asc,des,lead,lineWidth);
    
    //獲取一行文字最佳可視範圍（會把所有文字都包含進去）
    //    CGRect lineRect = CTLineGetImageBounds(firstLine, context);
    //    NSLog(@"整行的範圍:%@",NSStringFromCGRect(lineRect));
    
CGContextRestoreGState(context);

}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    NSMutableAttributedString *attributedStr = [[NSMutableAttributedString alloc] initWithString:@"北京出現嚴重霧霾後，網友紛紛給PM2.5取中文名字。嚴肅點就叫“公霧源”，高端點就叫“京塵”，霸氣點就叫“塵疾思汗”，樂觀點就叫“塵世美”，娛樂點就叫“塵慣吸”。但直到那五個字映入眼簾，才明白了中文的強大和詞彙的無窮魅力：喂人民服霧！"];
    [self setAttributedStringParagraphStyle:attributedStr];
//    [self setAttributesStringAttributes:attributedStr];

    CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef) attributedStr);
    CGMutablePathRef path = CGPathCreateMutable();
    CGRect bounds = CGRectInset((CGRect) {{20, 100}, {CGRectGetWidth(self.bounds) - 40, 400}}, 10.0f, 10.0f);
    CGPathAddRect(path, NULL, bounds);
    CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL);
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context, 0, self.bounds.size.height);//轉換CTM
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextSaveGState(context);//向圖形狀態棧中保存context狀態
    
    //ctLine的相關操作
    ctLineAndRun(frame);
    
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);//重置畫布
    CGContextAddPath(context, path);
    CGContextSetFillColorWithColor(context, [UIColor yellowColor].CGColor);
    CGContextFillPath(context);
    
    //CTLineGetImageBounds的應用，獲取一行文字的範圍， 就是指把這一行文字點有的像素矩陣作爲一個image圖片，來得到整個矩形區域
    CFArrayRef Lines = CTFrameGetLines(frame);
    int lineCount = CFArrayGetCount(Lines);
    
    CGPoint origins[lineCount];
    CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), origins);
    NSInteger lineIndex = 0;
    
    for (id oneLine in (NSArray *)Lines) {
        //相對於每一行基線原點的偏移量和寬高（例如：{{1.2， -2.57227}, {208.025, 19.2523}}，就是相對於本身的基線原點向右偏移1.2個單位，向下偏移2.57227個單位，後面是寬高）
        CGRect lineBounds = CTLineGetImageBounds((CTLineRef)oneLine, context);
        
        //每一行的起始點（相對於context）加上相對於本身基線原點的偏移量
        lineBounds.origin.x += origins[lineIndex].x + 30;
        lineBounds.origin.y += origins[lineIndex].y + 110;
        
        lineIndex++;
        
        //填充
        CGContextSetStrokeColorWithColor(context, [[UIColor redColor] CGColor]);
        CGContextSetLineWidth(context, 1.0);
        //設置長方形4個頂點
        CGPoint points[] = {CGPointMake(lineBounds.origin.x, lineBounds.origin.y), CGPointMake(lineBounds.origin.x + lineBounds.size.width, lineBounds.origin.y), CGPointMake(lineBounds.origin.x + lineBounds.size.width, lineBounds.origin.y + lineBounds.size.height), CGPointMake(lineBounds.origin.x, lineBounds.origin.y + lineBounds.size.height)};
        CGContextAddLines(context, points, 4);
        CGContextClosePath(context);
        CGContextStrokePath(context);
    }
    
    //畫
    CTFrameDraw(frame, context);
    CGPathRelease(path);
    CFRelease(frame);
    CFRelease(frameSetter);
    
    //恢復狀態棧中原有的狀態
    CGContextRestoreGState(context);
}

- (void)setAttributesStringAttributes:(NSMutableAttributedString *)attributedString
{
    //設置字體
    CTFontRef font = CTFontCreateWithName(CFSTR("Georgia"), 20, NULL);
    [attributedString addAttribute:(id)kCTFontAttributeName value:(id)font range:NSMakeRange(0, 4)];
    
    //設置字間距
    long kernNumber = 5;
    CFNumberRef kernNum = CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt8Type, &kernNumber);
    [attributedString addAttribute:(id)kCTKernAttributeName value:(id)kernNum range:(NSRange){0, 4}];
    
    //設置字體顏色
    long strokeNumber = 2;
    CFNumberRef strokeNum = CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt8Type, &strokeNumber);
    [attributedString addAttribute:(id)kCTStrokeWidthAttributeName value:(id)strokeNum range:(NSRange){0, 4}];
    [attributedString addAttribute:(id)kCTStrokeColorAttributeName value:(id)[UIColor redColor].CGColor range:NSMakeRange(0, 4)];
    
    //設置下劃線
    [attributedString addAttribute:(id)kCTUnderlineStyleAttributeName value:(id)[NSNumber numberWithInt:kCTUnderlineStyleSingle] range:NSMakeRange(0, 4)];
    [attributedString addAttribute:(id)kCTUnderlineStyleAttributeName value:(id)[UIColor redColor] range:(NSRange){0, 4}];
    
    //多屬性設置
    UIColor *color = [UIColor redColor];
    NSMutableDictionary *attributes = [[NSMutableDictionary alloc] initWithObjectsAndKeys:(id)font, kCTFontAttributeName, kernNum, kCTKernAttributeName, color.CGColor, kCTForegroundColorAttributeName, nil];
    [attributedString setAttributes:attributes range:NSMakeRange(0, 4)];
}

- (void)setAttributedStringParagraphStyle:(NSMutableAttributedString *)attributedString
{
    //對齊方式
    CTTextAlignment textAlignment = kCTLeftTextAlignment;
    CTParagraphStyleSetting alignmentStyleSetting;
    alignmentStyleSetting.spec = kCTParagraphStyleSpecifierAlignment;
    alignmentStyleSetting.valueSize = sizeof(textAlignment);
    alignmentStyleSetting.value = &textAlignment;
    
    //首行縮進
    CGFloat firstLineIndentSize = 55.0f;
    CTParagraphStyleSetting firstLineIndent;
    firstLineIndent.spec = kCTParagraphStyleSpecifierFirstLineHeadIndent;
    firstLineIndent.value = &firstLineIndentSize;
    firstLineIndent.valueSize = sizeof(float);
    
    //段前縮進（文字左側距離context最左側的距離）
    CGFloat headIndentSize = 20.0f;
    CTParagraphStyleSetting headIndent;
    headIndent.spec = kCTParagraphStyleSpecifierHeadIndent;
    headIndent.valueSize = sizeof(float);
    headIndent.value = &headIndentSize;
    
    //斷尾縮進(文字右側距離context最左側的距離)
    CGFloat tailIndentSize = 251.0f;    //文字最左側到文字最右側的距離
    CTParagraphStyleSetting tailIndent;
    tailIndent.spec = kCTParagraphStyleSpecifierTailIndent;
    tailIndent.value = &tailIndentSize;
    tailIndent.valueSize = sizeof(float);
    
    //換行模式
    CTLineBreakMode lineBreak = kCTLineBreakByCharWrapping;
    CTParagraphStyleSetting lineBreakMode;
    lineBreakMode.spec = kCTParagraphStyleSpecifierLineBreakMode;
    lineBreakMode.value = &lineBreak;
    lineBreakMode.valueSize = sizeof(CTLineBreakMode);
    
    //最大行高
    CGFloat maxHeightSize = 50.0f;  //最大行高不能超過50個像素，超過按照最大像素來
    CTParagraphStyleSetting maxHeightSetting;
    maxHeightSetting.spec = kCTParagraphStyleSpecifierMaximumLineHeight;
    maxHeightSetting.value = &maxHeightSize;
    maxHeightSetting.valueSize = sizeof(float);
    
    //多行高
    CGFloat multipleHeight = 1.2f;  //1.2倍原來的高度
    CTParagraphStyleSetting multipleHeightSetting;
    multipleHeightSetting.spec = kCTParagraphStyleSpecifierLineHeightMultiple;
    multipleHeightSetting.value = &multipleHeight;
    multipleHeightSetting.valueSize = sizeof(float);
    
    //最大行距
    CGFloat maxLineSpace = 5.0f;//最大行距不能超過5像素，超過了按最大行距畫圖，最小行距同理，行距調整隻在中間值中進行
    CTParagraphStyleSetting maxLineSpaceSetting;
    maxLineSpaceSetting.spec = kCTParagraphStyleSpecifierMaximumLineSpacing;
    maxLineSpaceSetting.valueSize = sizeof(float);
    maxLineSpaceSetting.value = &maxLineSpace;
    
    //行距
    CGFloat lineSpace = 25.0f;  //行距25像素
    CTParagraphStyleSetting lineSpaceSetting;
    lineSpaceSetting.spec = kCTParagraphStyleSpecifierLineSpacing;
    lineSpaceSetting.value = &lineSpace;
    lineSpaceSetting.valueSize = sizeof(float);
    
    //段前間隔
    CGFloat paragraghSpace = 15.0f;
    CTParagraphStyleSetting paragraghInterval;
    paragraghInterval.spec = kCTParagraphStyleSpecifierParagraphSpacing;
    paragraghInterval.valueSize = sizeof(float);
    paragraghInterval.value = ¶graghSpace;
    
    CTParagraphStyleSetting settingsArray[] = {alignmentStyleSetting, firstLineIndent, headIndent, tailIndent, lineBreakMode, maxLineSpaceSetting, multipleHeightSetting, lineSpaceSetting, maxLineSpaceSetting, paragraghInterval};
    
    //採用setting裏面前10個的段落設置，不夠10個，就按照setting擁有的最大段落設置個數來算
    CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(settingsArray, 10);
    NSDictionary *paragraphStyleDic = [[NSDictionary alloc] initWithObjectsAndKeys:(id)paragraphStyle, kCTParagraphStyleAttributeName, nil];
    [attributedString setAttributes:paragraphStyleDic range:(NSRange){0, [attributedString length]}];
}

- (void)ctLineAndRun
{
    
}

@end

關於CoreText的官方API：

https://developer.apple.com/library/mac/#documentation/Carbon/Reference/CoreText_Framework_Ref/_index.html