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CoreText是iOS3.2推出的一套文字排版和渲染框架,可以实现图文混排,富文本显示等效果。
CoreText中的几个重要的概念:
先来了解一下该框架的整体视窗组合图:
CTFrame 作为一个整体的画布(Canvas),其中由行(CTLine)组成,而每行可以分为一个或多个小方块(CTRun)。
注意:你不需要自己创建CTRun,Core Text将根据NSAttributedString的属性来自动创建CTRun。每个CTRun对象对应不同的属性,正因此,你可以自由的控制字体、颜色、字间距等等信息。
此外还有一点需要注意:一个CTRun是不能跨行的,若是一段文字拥有相同的属性,且跨行,则会被分在多个CTRun当中,每个CTRun拥有相同属性。
首先来看看使用Coretext的基本步骤:
第一步:
要有一个NSMutableAttributedString,用一个字符串来初始化NSMutableAttributedString。
NSMutableAttributedString * _mString = [[NSMutableAttributedString alloc] initWithString:_text];
第二步:对NSMutableAttributedString进行属性设置。
[_mString beginEditing];
[_mString addAttributes:textAttribute.attributeDic range:attr.range];
[_mString addAttribute:@"MTText" value:attr.text range:attr.range];
[_mString endEditing];
在这里有两种方式,一个是设置单个属性,一个是直接批量设置属性。属性的key值可以是自己定义的。
以下是一些常见的属性设置
1.设置字体属性
CTFontRef font = CTFontCreateWithName(CFSTR("Georgia"), 40, NULL); [_mString addAttribute:(id)kCTFontAttributeName value:(id)font range:NSMakeRange(0, 4)];
2.设置斜体字
CTFontRef font = CTFontCreateWithName((CFStringRef)[UIFont italicSystemFontOfSize:20].fontName, 14, NULL); [_mString addAttribute:(id)kCTFontAttributeName value:(id)font range:NSMakeRange(0, 4)];
3.设置连字
long number = 1; CFNumberRef num = CFNumberCreate(kCFAllocatorDefault,kCFNumberSInt8Type,&number); [mabstring addAttribute:(id)kCTLigatureAttributeName value:(id)num range:NSMakeRange(0, [str length])];
4.设置下划线
[_mString addAttribute:(id)kCTUnderlineStyleAttributeName value:(id)[NSNumber numberWithInt:kCTUnderlineStyleDouble] range:NSMakeRange(0, 4)];
5.设置下划线颜色
[_mString addAttribute:(id)kCTUnderlineColorAttributeName value:(id)[UIColor redColor].CGColor range:NSMakeRange(0, 4)];
6.设置字体间隔
long number = 10; CFNumberRef num = CFNumberCreate(kCFAllocatorDefault,kCFNumberSInt8Type,&number); [_mString addAttribute:(id)kCTKernAttributeName value:(id)num range:NSMakeRange(10, 4)];
最后是画出对应的图像了
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context , 0 ,self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString( (CFAttributedStringRef) _mString); CGMutablePathRef path = CGPathCreateMutable(); CGRect rects = CGRectMake(0 , 0 ,self.bounds.size.width , self.bounds.size.height); CGPathAddRect(path, NULL , rects); CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL); _frameRef = frame; CTFrameDraw(frame,context); CGPathRelease(path); CFRelease(frameSetter);
这里有几点比较需要注意:
1.坐标转换问题。在使用CGcontext进行绘制时坐标轴圆点在屏幕左下方,而UIKit得坐标系圆点在左上方,需要对此进行转换。此外,在后面的操作中也要用到坐标变换。
2.文字的绘画区域不是整个context,而是在CTFrameRef中,后面我们还会碰到相关的问题。
CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL);
现在我们已经能设置文字的基本属性了,但富文本中还有比较重要的一个应用:图文混排
我们先来说说实现图文混排的基本思路。
coretext是直接绘制在layer层上的,我们可以在drawRect 方法中直接画一张图片,只要将图片放在适合的位置,就实现了图文混排。
现在的关键是如何计算出图片所在的位置,此外,当图片添加的时候,文字的排版要如何调整问题。
为了能插入图片,首先我们要设置一个占位符,正常设置为空格符,因为图片如果没有完全覆盖那个区域,可能显示出占位符。当然你也可以任意设置一个字符并将其
的颜色设置为clearColor。设置占位符后我们要为它设置属性,
记住,要为它设置一个单独的属性,不能与相邻的字符属性一致,因为这样系统可能因此将他们合并在一个CTRun当中。
占位符最好只设置一个,如果占位符是多个的话,有可能占位符处于不同行,会被分成两个CTRun,此时图片就可能超出屏幕边界。
NSMutableAttributedString *replaceStr = [[NSMutableAttributedString alloc] initWithString:@"1"];
UIColor *color = [UIColor clearColor];
NSRange range = NSMakeRange(_mString.length - 1, 1);
[replaceStr addAttribute:(id)color.CGColor value:(id)kCTForegroundColorAttributeName range:range];
[_mString appendAttributedString:replaceStr];
设置完占位符基本属性后,我们需要设置占位符对应得CTRun的回调方法来设置CTRun的大小,以适应图片。 CTRunDelegateCallbacks imageCallBacks;
imageCallBacks.version = kCTRunDelegateVersion1; imageCallBacks.dealloc = RunDelegateDeallocCallback; imageCallBacks.getAscent = RunDelegateGetAsent; imageCallBacks.getDescent = RunDelegateGetDescent; imageCallBacks.getWidth = RunDelegateGetWidthCallBack;
//传入的参数attr.text可以在回调方法中使用 CTRunDelegateRef runDelegate = CTRunDelegateCreate(&imageCallBacks, (__bridge void *)(attr.text)); CTRunDelegateGetRefCon(runDelegate); [_mString addAttribute:(NSString *)kCTRunDelegateAttributeName value:(__bridge id)runDelegate range:attr.range]; [_mString addAttribute:@"imageName" value:attr.text range:attr.range]; CFRelease(runDelegate);
void RunDelegateDeallocCallback{
}
CGFloat RunDelegateGetAsent(void *refCon) {
NSString *imageName = (__bridge NSString *)(refCon);
return [UIImage imageNamed:imageName].size.height;
}
CGFloat RunDelegateGetDescent(void *refCon) {
return 0;
}
CGFloat RunDelegateGetWidth(void *refCon) {
NSString *imageName = (__bridge NSString *)(refCon);
return [UIImage imageNamed:imageName].size.width;
}
在设置好属性还有回调方法之后,就可以开始绘制图片了。
基本的思路是获取文本的每一行,再获取每一个CTRun,根据属性来判断是否是绘制图片的点,是的话则获取绘画区域,绘制图片。
CFArrayRef lines = CTFrameGetLines(_frameRef); CGPoint origins[CFArrayGetCount(lines)]; CTFrameGetLineOrigins(_frameRef, CFRangeMake(0, 0), origins); NSMutableArray *attrArray = [[NSMutableArray alloc] init]; for (int i = 0; i < CFArrayGetCount(lines); i ++) { CTLineRef line = CFArrayGetValueAtIndex(lines, i); CFArrayRef runs = CTLineGetGlyphRuns(line); for (int k = 0; k < CFArrayGetCount(runs); k ++) { CTRunRef run = CFArrayGetValueAtIndex(runs, k); NSDictionary *attri = (NSDictionary *)CTRunGetAttributes(run); NSString *imageName = [attri objectForKey:@"imageName"]; if (imageName) { CGFloat runAsent; CGFloat runDescent; CGPoint origin = origins[i]; CGRect runRect; runRect.size.width = CTRunGetTypographicBounds(run, CFRangeMake(0, 0), &runAsent, &runDescent, NULL); CGFloat offset = CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, NULL); runRect = CGRectMake(origin.x + offset, origin.y - runDescent, runRect.size.width, runAsent + runDescent);
UIImage *image = [UIImage imageNamed:imageName];
CGContextDrawImage(context, runRect, image.CGImage);
}
}
}
这里有个需要注意的点,我们取到得位置是相对于整个画布,而不是相对于所在的View的位置
CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, NULL);
因此,如果CTFrameref如果有不在原点,计算时需要加上这部分的偏移量。
点击事件和图片绘制差不多,获取点击的点,进行坐标变换
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{ UITouch *touch = touches.anyObject; CGPoint point = [touch locationInView:self];
//坐标变换 CGPoint location = CGPointMake(point.x, self.bounds.size.height - point.y); MTLabelAttribute *attr = [self getAttributeByLocation:location]; _lastAttr = attr; if (attr) { if ([self.delegate respondsToSelector:@selector(clickWithAttibute:andText:)]) { [self.delegate clickWithAttibute:attr andText:attr.text]; } [self setAttributeWithType:@"hightlight" andAttribute:attr]; } //判断point是否在点击的文字范围内 }
先判断在哪一行,然后判断点击的点在哪一个CTRun上。在这里要注意所要实现点击的字符串可能跨行的情况。
- (MTLabelAttribute *)getAttributeByLocation:(CGPoint) point{ NSArray *lines = (NSArray *)CTFrameGetLines(_frameRef); CGPoint origins[lines.count]; CTFrameGetLineOrigins(_frameRef, CFRangeMake(0, 0), origins); CTLineRef ref; int count = 0;
//判断所在的行 if (point.y < origins[lines.count - 1].y) { return nil; } for (int i = 1; i < lines.count ; i ++) { CGFloat minY = origins[i].y; CGFloat maxY = origins[i - 1].y; if (point.y >= minY && point.y <= maxY) { count = i ; break; } } ref = (__bridge CTLineRef)lines[count]; CGPoint origin = origins[count]; NSArray *ctRuns = (NSArray *)CTLineGetGlyphRuns(ref); //判断所在的CTRun for (int k = 0; k < ctRuns.count; k ++) { CTRunRef runTest = (__bridge CTRunRef)([ctRuns objectAtIndex:k]); CGFloat offset = CTLineGetOffsetForStringIndex((CTLineRef)lines[count], CTRunGetStringRange(runTest).location, NULL) + 0.0; CGPoint firstPoint = CGPointMake(origin.x + offset , origin.y); CGFloat ascent; CGFloat descent; CGFloat leading; CGFloat width = CTRunGetTypographicBounds(runTest, CFRangeMake(0, 0), &ascent, &descent, &leading); if ( point.x >= firstPoint.x &&point.x <= firstPoint.x + width &&point.y <= origin.y + ascent &&point.y >= origin.y ) { NSDictionary *dic = (NSDictionary *)CTRunGetAttributes(runTest); NSString *string = [dic objectForKey:@"MTText"]; CFRange cfRange = CTRunGetStringRange(runTest); if ([dic objectForKey:@"imageName"]) { return [self getAttributesWithRange:NSMakeRange(cfRange.location, cfRange.length)]; }
//跨行情况处理 NSString *subString = [self.text substringWithRange: NSMakeRange(cfRange.location, cfRange.length)]; NSRange range; NSRange subStringRange = [string rangeOfString:subString]; range = NSMakeRange(cfRange.location - subStringRange.location, string.length); return [self getAttributesWithRange:range]; } } return nil; }
最后,是Gif的显示
gif是比较特殊的一种情况,处理起来也比较麻烦。对于gif有两种展示方式,一种是用一个专门的UIView来展示,然后用添加subView的方式使用。用这种方式可以使用
第三方的框架,使用UIWebView播放等,也可以自己写,下面是使用UIImageView的方式:详情可看http://www.cocoachina.com/bbs/read.php?tid=124430
UIImageView *gifImageView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; NSArray *gifArray = [NSArray arrayWithObjects:[UIImage imageNamed:@"1"], [UIImage imageNamed:@"2"], [UIImage imageNamed:@"3"], [UIImage imageNamed:@"4"], [UIImage imageNamed:@"5"], [UIImage imageNamed:@"6"], [UIImage imageNamed:@"7"], [UIImage imageNamed:@"8"], [UIImage imageNamed:@"9"], [UIImage imageNamed:@"10"], [UIImage imageNamed:@"11"], [UIImage imageNamed:@"12"], [UIImage imageNamed:@"13"], [UIImage imageNamed:@"14"], [UIImage imageNamed:@"15"], [UIImage imageNamed:@"16"], [UIImage imageNamed:@"17"], [UIImage imageNamed:@"18"], [UIImage imageNamed:@"19"], [UIImage imageNamed:@"20"], [UIImage imageNamed:@"21"], [UIImage imageNamed:@"22"],nil]; gifImageView.animationImages = gifArray; //动画图片数组 gifImageView.animationDuration = 5; //执行一次完整动画所需的时长 gifImageView.animationRepeatCount = 1; //动画重复次数 [gifImageView startAnimating]; [self.view addSubview:gifImageView]; [gifImageView release];
使用UIImageView的方式是固定的时间间隔,但gif并非每一帧的间隔都一样,因此有些情况可能达不到最好的播放效果。
在IOS7之后可以使用TextKit中的attachment,直接添加UIWebView播放Gif图片,YYTextKit中也有类似的实现。
如果我们要手动实现的话,那就只好一帧一帧的往屏幕上画了。我们首先来看看继承UIView的实现方式,记住不能继承自caLayer,虽然最后是在layer层绘画,
但直接继承calyer,然后用addsublayer方法显示,图像会有重影,大概UIView中有对其进行处理。
首先用一个类对Gif图片进行解析
@interface MTGifAttribute : NSObject @property (nonatomic, strong, readonly) NSArray *imageFrames; @property (nonatomic, strong, readonly) NSArray *properties; @property (nonatomic, strong, readonly) NSArray *delayTimes; @property (nonatomic, assign, readwrite) UIView<MTGifProtocol> * delegate; @property (nonatomic, assign, readwrite) CGRect frame; //@property (nonatomic, copy) NSString *path; @property (nonatomic, assign, readonly) NSInteger index; - (void)setImageInfoWithFilePath:(NSString *)path; - (void)startAnitation; @end
解析方法
@implementation MTGifAttribute - (instancetype)init{ self = [super init]; if (self) { _index = 0; } return self; } - (void)setImageInfoWithFilePath:(NSString *)path { NSMutableArray *imageFrames = [[NSMutableArray alloc] init]; NSMutableArray *delayTimes = [[NSMutableArray alloc] init]; NSURL *filrUrl = [NSURL fileURLWithPath:path]; CFURLRef cfUrl = (__bridge CFURLRef)filrUrl; CGImageSourceRef gifSource = CGImageSourceCreateWithURL(cfUrl, NULL); NSInteger count = CGImageSourceGetCount(gifSource); for (int i = 0; i < count; i++){ CGImageRef frame = CGImageSourceCreateImageAtIndex(gifSource, i, NULL); [imageFrames addObject:(__bridge id)frame]; CGImageRelease(frame); NSDictionary *dic = CFBridgingRelease(CGImageSourceCopyPropertiesAtIndex(gifSource, i, NULL)); NSDictionary *gifDic =[dic valueForKey:(NSString *)kCGImagePropertyGIFDictionary]; [delayTimes addObject:[gifDic objectForKey:(NSString *)kCGImagePropertyGIFDelayTime]]; } NSDictionary *dic = CFBridgingRelease(CGImageSourceCopyPropertiesAtIndex(gifSource, 0, NULL)); CGFloat gifWidth = (CGFloat)[[dic valueForKey:(NSString*)kCGImagePropertyPixelWidth] floatValue]; CGFloat gifHeight = (CGFloat)[[dic valueForKey:(NSString*)kCGImagePropertyPixelHeight] floatValue]; _frame = CGRectMake(0, 0, gifWidth, gifHeight); _imageFrames = imageFrames; _delayTimes = delayTimes; } - (void)startAnitation { [self changeImage]; } - (void)changeImage {
//代理方法,调用setNeeddisplay if ([self.delegate respondsToSelector:@selector(disPlayInRect:)]) { [self.delegate disPlayInRect:self.frame]; }else{ return; } _index ++; _index = _index % self.imageFrames.count; CGFloat delay = [[self.delayTimes objectAtIndex:_index] floatValue]; dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ [self changeImage]; }); }
图片索引切换方法
- (void)startAnitation { [self changeImage]; } - (void)changeImage { if ([self.delegate respondsToSelector:@selector(disPlayInRect:)]) { [self.delegate disPlayInRect:self.frame]; }else{ return; } _index ++; _index = _index % self.imageFrames.count; CGFloat delay = [[self.delayTimes objectAtIndex:_index] floatValue]; dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ [self changeImage]; }); }
继承UIView,重写drawRect方法。
- (void)drawRect:(CGRect)rect{ CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextTranslateCTM(ctx , 0 ,self.frame.size.height); CGContextScaleCTM(ctx, 1.0, -1.0); UIImage *image = [_gifImage.imageFrames objectAtIndex:_index]; CGImageRef cgimage = image.CGImage; UIGraphicsBeginImageContext(CGSizeMake(self.frame.size.width, self.frame.size.height)); CGContextDrawImage(ctx, _gifImage.frame, cgimage); }
至此Gif的显示已经完成,但有些时候我们不想单独用一个view来显示。而是想用coretext图文混排的方式来显示,将gif和文字显示在同一个view。
此时的方式和用一个单独的view显示一样,只是绘画的对象不同而已。
比较需要注意的一个点是,在每次重绘的时候,因为gif不断地重绘,如果每次都刷新整个View的话有可能会造成性能问题。因此可以使用
[self setNeedsDisplayInRect:rect];方法,只刷新gif所在区域。
当然,在这种情况下也要万分注意左边变换问题,如果刷新的区域,与变换坐标后的绘画区域不对应,图片会消失或者只显示部分。
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原文地址:http://www.cnblogs.com/bigly/p/5796684.html