iOS阅读器实践系列图文混排

Posted 2020-08-18 晴天10

本篇介绍coretext中的图文混排，这里暂用静态的内容，即在文本中某一固定位置插入图片，而不是插入位置是根据文本内容动态插入的（要实现这一效果需要写一个文本解析器，将原信息内容解析为某些特定格式的结构来标示出特定的类型（比如文字、图片、链接等），然后按照其结构中的属性配置，生成属性字符串，之后渲染到视图中）。

这部分的思路参考唐巧大神的blog。

在第一篇介绍过coretext是离屏渲染的，即在将内容渲染到屏幕上之前，coretext已完成排版工作。coretext排版的第一步是组织数据，即由原始字符串通过特定的配置来得到属性字符串。实现在文字中插入图片的大部分工作都是在这一步中完成的。

大体思路是：首先将原始纯文本数据通过预定义的配置生成相应的属性字符串A，然后生成一个字符作为占位符（绘制时在这个占位符中填充图片），根据特定的配置生成属性字符串B，然后将B插入到A相应位置，最后将合并后的A和图片渲染到视图中。

具体步骤如下：

一、创建存储A的数据结构CoreTextData与存储B的数据结构CTImgData

二、生成属性字符串A

三、生成属性字符串B

四、检测图片位置，以便后续对图片操作进行处理

 

1、创建存储A的数据结构CoreTextData与存储B的数据结构CTImgData

在实际开发中我们需要一个结构来存储排版和业务的一些数据，首先介绍CoreTextData：

@interface CoreTextData : NSObject

@property (assign, nonatomic) CTFrameRef ctFrame;
@property (assign, nonatomic) CGFloat height;
@property (strong, nonatomic) NSMutableAttributedString *content;

@property (nonatomic, strong) NSMutableArray *imgDataArray;

@property (nonatomic, assign) NSInteger characterNum;

@end

代码中列出了，排版和业务上可能用的一些数据（当然你完全可以根据自己的需求来定义结构，这里只是举了一些我觉得可能用到的字段），其中CTFrame用于文本渲染，height记录的属性字符串排版时所需的高度，content保存了文本内容，imgDataArray是保存CTImgData的数组，characterNum记录的content的字数。

CoreTextImgData结构：

@interface CoreTextImgData : NSObject

@property (strong, nonatomic) NSString *name;
@property (nonatomic) NSUInteger position;

@property (nonatomic, assign) CGFloat leftMargin;
@property (nonatomic, assign) CGFloat topMargin;

//坐标系为coreText坐标系，而不是UIKit坐标系
@property (nonatomic) CGRect imgPosition;

@property (nonatomic, assign) BOOL isResponseTap;

- (void)handleImgTapped:(NSInteger)chapterId chapterTitle:(NSString *)title;

@end

name表示所用图片的名字，position表示图片在文本中的字符索引，leftMargin和topMargin用于排版时图片位置的调整（距左边与上边的间隔），图片在视图中坐标（coretext坐标系），isResponseTap表示图片是否响应点击，下面的方法是处理图片的事件的，后面介绍。

 

生成文本与图片的属性字符串

contentString = [[NSMutableAttributedString alloc] initWithString:content attributes:attributes];

//bottom line
        CGFloat bottomLineW = viewWidth - 20;
        NSDictionary *bottomImgDict = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:bottomLineW], @"width", [NSNumber numberWithFloat:1], @"height", @"Line", @"imgName", nil];
        CoreTextImgData *bottomImgData = [[CoreTextImgData alloc] init];
        bottomImgData.position = contentString.length;
        bottomImgData.name = bottomImgDict[@"imgName"];
        [imgDataArray addObject:bottomImgData];
        NSDictionary *bottomImgAttributes = [manager getAditionLineAttribute];
        NSAttributedString *bottomLineContent = [self getImageAttributeContentWithDictionary:bottomImgDict attribute:bottomImgAttributes isLineFeed:YES imgName:bottomImgData.name imgData:bottomImgData leftMargin:10 topMargin:0];
        
        [contentString appendAttributedString:bottomLineContent];

+ (NSAttributedString *)getImageAttributeContentWithDictionary:(NSDictionary *)dict attribute:(NSDictionary *)attribute isLineFeed:(BOOL)isLineFeed imgName:(NSString *)imgName imgData:(CoreTextImgData *)imgData leftMargin:(CGFloat)leftMargin topMargin:(CGFloat)topMargin
{
    CTRunDelegateCallbacks callbacks;
    memset(&callbacks, 0, sizeof(CTRunDelegateCallbacks));
    callbacks.version = kCTRunDelegateVersion1;
    callbacks.getAscent = ascentCallback;
    callbacks.getDescent = descentCallback;
    callbacks.getWidth = widthCallback;
    CTRunDelegateRef delegate = CTRunDelegateCreate(&callbacks, (__bridge void * _Nullable)(dict));
    
    unichar objectReplacementChar = 0xFFFC;
    NSString *imgContent = [NSString stringWithCharacters:&objectReplacementChar length:1];
    NSMutableAttributedString *space = nil;
    if (isLineFeed)
    {
        imgContent = [NSString stringWithFormat:@"\n%@", imgContent];
        space = [[NSMutableAttributedString alloc] initWithString:imgContent attributes:attribute];
        CFAttributedStringSetAttribute((CFMutableAttributedStringRef)space, CFRangeMake(1, space.length - 1), kCTRunDelegateAttributeName, delegate);
        [space addAttribute:@"imgName" value:imgName range:NSMakeRange(1, space.length - 1)];
        
        imgData.position += 1;
    }
    else
    {
        space = [[NSMutableAttributedString alloc] initWithString:imgContent attributes:attribute];
        CFAttributedStringSetAttribute((CFMutableAttributedStringRef)space, CFRangeMake(0, space.length), kCTRunDelegateAttributeName, delegate);
        [space addAttribute:@"imgName" value:imgName range:NSMakeRange(0, space.length)];
    }
    
    imgData.leftMargin = leftMargin;
    imgData.topMargin = topMargin;
    
    CFRelease(delegate);
    return space;
}

static CGFloat ascentCallback(void *ref) {
    return [[(__bridge NSDictionary *)ref objectForKey:@"height"] floatValue];
}

static CGFloat descentCallback(void *ref){
    return 0;
}

static CGFloat widthCallback(void* ref){
    return [(NSNumber*)[(__bridge NSDictionary*)ref objectForKey:@"width"] floatValue];
}

 

这里是在contentString后插入一条直线。bottomImgDict定义了图片的一些属性然后将某些属性存入CoreTextImgData中，然后将这个CoretextImgData存入imgDataArray中用于往视图中依次渲染。

下面方法用于生成图片的属性字符串，首先是根据传入的属性字典得到图片的宽高信息，然后定义占位字符0xFFFC，isLineFeed表示是否需要换行，利用占位字符生成属性字符串，配置相应属性，在换行条件中因为在拼接字符串时在占位符前加了一个换行符，故占位符的索引需要加一，对应 imgData.position += 1，返回占位符生成的属性字符串，最后将其拼接到原有属性字符串的后面。

 

检测图片位置，以便后续对图片操作进行处理：

+ (void)fillImagePositionWithCTFrame:(CTFrameRef)ctFrame coreTextData:(CoreTextData *)coreTextData imageDataArray:(NSMutableArray *)arrImgData
{
    if (arrImgData == nil || arrImgData.count == 0)
    {
        return;
    }
    
    int imgIndex = 0;
    CoreTextImgData *imageData = arrImgData[0];
    
    CFRange frameRange = CTFrameGetVisibleStringRange(ctFrame);
    
//在多页显示的情况下，while循环确保当前的imgData是包含在当前CTFrame中的，比如第一页有两个图片，第二页有一个图片，如果当前的CTFrame是第二页的，那么while循环完成时imgIndex = 2
    while ( imageData.position < frameRange.location ) {
        imgIndex++;
        if (imgIndex>=[arrImgData count]) return; //quit if no images for this column
        imageData = [arrImgData objectAtIndex:imgIndex];
    }
    
    NSArray *lines = (NSArray *)CTFrameGetLines(ctFrame);
    NSUInteger lineCount = lines.count;
    CGPoint lineOrigins[lineCount];
    CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), lineOrigins);
    
    for (int i = 0; i < lineCount; ++i)
    {
        if (imageData == nil)
        {
            break;
        }
        
        CTLineRef line = (__bridge CTLineRef)(lines[i]);
        NSArray *runObjArray = (NSArray *)CTLineGetGlyphRuns(line);
        for (id runObj in runObjArray)
        {
            CTRunRef run = (__bridge CTRunRef)runObj;
            
            CFRange runRange = CTRunGetStringRange(run);
//            NSDictionary *runAttributesDict = (NSDictionary *)CTRunGetAttributes(run);
//            NSString *imgName = [runAttributesDict objectForKey:@"imgName"];
            //确保图片的字符索引在当前runRange范围内
            if (runRange.location <= imageData.position && runRange.location + runRange.length > imageData.position)
            {
                NSDictionary *runAttributes = (NSDictionary *)CTRunGetAttributes(run);
                CTRunDelegateRef delegate = (__bridge CTRunDelegateRef)[runAttributes valueForKey:(id)kCTRunDelegateAttributeName];
                
                if (delegate == nil)
                {
                    continue;
                }

                CGRect runBounds;
                CGFloat ascent;
                CGFloat descent;
                runBounds.size.width = CTRunGetTypographicBounds(run, CFRangeMake(0, 0), &ascent, &descent, NULL);
                runBounds.size.height = ascent + descent;
                
                CGFloat xOffset = CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, NULL);
                runBounds.origin.x = lineOrigins[i].x + xOffset + imageData.leftMargin;
                runBounds.origin.y = lineOrigins[i].y;
                runBounds.origin.y -= descent + imageData.topMargin;
                
                CGPathRef pathRef = CTFrameGetPath(ctFrame);
                CGRect colRect = CGPathGetBoundingBox(pathRef);
                
                CGRect delegateBounds = CGRectOffset(runBounds, colRect.origin.x, colRect.origin.y);
                
                //得到图片在其所在CTFrame包含区域中的位置区域
                imageData.imgPosition = delegateBounds;
                
                [coreTextData.imgDataArray addObject:imageData];
                
                imgIndex++;
                if (imgIndex == arrImgData.count)
                {
                    imageData = nil;
                    break;
                }
                else
                {
                    imageData = arrImgData[imgIndex];
                }
            }
        }
    }
}

上面方法主要目的是获取图片的位置区域，用于图片点击。即代码中的注释部分，前面的的代码都是为获取这个区域所做的准备。

我是在排版内容时调用上述方法，内容生成多少个CTFrame该方法就会调用多少次：

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)mabStr);
    
    NSMutableArray *coreTextDatas = [[NSMutableArray alloc] init];
    int textPos = 0;
    while (textPos < mabStr.length)
    {
        //得到每页的尺寸
        CGFloat aOriginY;
        CGFloat frameHeight;
        if (textPos == 0)
        {
            aOriginY = firstOriginY;
        }
        else
        {
            aOriginY = originY;
        }
        
        frameHeight = [self getFrameHeight:framesetter viewWidth:viewWidth viewHeight:viewHeight flipDirection:manager.flipOverDirection] - aOriginY - bottomMargin;
        
        
        // 生成 CTFrameRef 实例
        CGFloat finalOriginY = bottomMargin;  //将UIKit坐标系下y轴的偏移aOriginY转化为coretext坐标系下的偏移
        
        CTFrameRef frame = [self createFrameWithFramesetter:framesetter frameWidth:viewWidth stringRange:CFRangeMake(textPos, 0) orginY:finalOriginY height:frameHeight];
        
        CFRange frameRange = CTFrameGetVisibleStringRange(frame);
        
        // 将生成好的 CTFrameRef 实例和计算好的绘制高度保存到 CoreTextData 实例中，最后返回 CoreTextData 实例
        CoreTextData *data = [[CoreTextData alloc] init];
        data.ctFrame = frame;
        data.height = frameHeight;        

        [self fillImagePositionWithCTFrame:data.ctFrame coreTextData:data imageDataArray:imgDataArray];
        NSAttributedString *aStr = [mabStr attributedSubstringFromRange:NSMakeRange(textPos, frameRange.length)];
        data.content = aStr;
        
        [coreTextDatas addObject:data];
        
        textPos += frameRange.length;
        
        // 释放内存
        CFRelease(frame);
    }
    
    // 释放内存
    CFRelease(framesetter);
    
    return coreTextDatas;

 

当在视图中点击图片时：可在视图类中定义如下方法：

- (void)setupEvents
{
    UIGestureRecognizer * tapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(userTapGestureDetected:)];
    tapRecognizer.delegate = self;
    [self addGestureRecognizer:tapRecognizer];
    self.userInteractionEnabled = YES;
}

//处理点击事件
- (void)userTapGestureDetected:(UIGestureRecognizer *)recognizer
{
    CGPoint point = [recognizer locationInView:self];
    CoreTextImgData *imgData = [self getTheResponsedImgData:point];
    if (imgData != nil)
    {
        [imgData handleImgTapped:_chapterId chapterTitle:_chapterTitle];
    }
}

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    CGPoint point = [gestureRecognizer locationInView:self];
    BOOL isDispatch = [self isPointInResponsedImgRect:point];
    if (isDispatch)
    {
        return YES;
    }
    
    return NO;
}

//翻转坐标系
- (CGRect)transformCTM:(CGRect)rect
{
    CGPoint originPoint = rect.origin;
    originPoint.y = self.bounds.size.height - rect.origin.y - rect.size.height;
    CGRect aRect = CGRectMake(originPoint.x, originPoint.y, rect.size.width, rect.size.height);
    
    return aRect;
}

- (BOOL)isPointInResponsedImgRect:(CGPoint)point
{
    for (CoreTextImgData *imgData in self.data.imgDataArray)
    {
        CGRect rect = [self transformCTM:imgData.imgPosition];
        if (CGRectContainsPoint(rect, point))
        {
            if (imgData.isResponseTap)
            {
                return NO;
            }
        }
    }
    
    return YES;
}

- (CoreTextImgData *)getTheResponsedImgData:(CGPoint)point
{
    for (CoreTextImgData *imgData in self.data.imgDataArray)
    {
        CGRect rect = [self transformCTM:imgData.imgPosition];
        if (CGRectContainsPoint(rect, point))
        {
            if (imgData.isResponseTap)
            {
                return imgData;
            }
        }
    }
    
    return nil;
}

然后在ImgData中处理具体的图片点击事件：

- (void)handleImgTapped:(NSInteger)chapterId chapterTitle:(NSString *)title
{
    if ([self.name isEqualToString:@"xxx"])
    {
        NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInteger:chapterId], @"chapterId", title, @"chapterTitle", nil];
        NSNotification *notification =[NSNotification notificationWithName:@"chpaterReply" object:nil userInfo:userInfo];
        [[NSNotificationCenter defaultCenter] postNotification:notification];
    }
}

这里通过imgData中name属性区分不同图片，进行不同处理。

 

PS：写的有点仓促，有些系统函数的作用没有介绍，如有不太清楚或错误的地方，欢迎交流。