CTLineDraw細(xì)節(jié)繪制
首先得了解字形，如下圖：
字形圖.png
步驟
1.<code>CTFrameGetLines</code>函數(shù)獲取行數(shù)
2.<code>CTFrameGetLineOrigins</code>函數(shù)獲取每行的坐標(biāo)
3.<code>CTLineGetTypographicBounds(line as! CTLine, &lineAscent, &lineDescent, &lineLeading)</code>獲得每行的字形
4.<code>
CGContextSetTextPosition(ctx, lineOrigin.x, lineOrigin.y)</code>根據(jù)實際情況微調(diào)坐標(biāo)
5.<code>CTLineDraw(line as! CTLine, ctx)</code>繪制某一行缎除。
首先繪制大多數(shù)情況都要需要高度器罐，那么現(xiàn)在來一個高度計算的大致思路:
/*
根據(jù)屬性字符串計算繪制所需要的高度
思路就是 lineAscent＋lineDescent ＋lineLeading代表一行的高度轰坊，分別對每一行進(jìn)行高度累加
*/
func getDisplayHeight(attributeStr: NSAttributedString,width:CGFloat) -> CGFloat{
let ctFrameSetter = CTFramesetterCreateWithAttributedString(attributeStr)
//建議的寬高
let suggestSize = CTFramesetterSuggestFrameSizeWithConstraints(ctFrameSetter, CFRangeMake(0, attributeStr.length), nil, CGSize(width: width, height: CGFloat.max), nil)
let path = CGPathCreateMutable()
CGPathAddRect(path, nil, CGRect(x: 0, y: 0, width: width, height: suggestSize.height*2))//2是假的蕴忆，只是防止畫布不夠大驻襟，計算有誤沉衣，下面才開始精確計算高度
let ctFrame = CTFramesetterCreateFrame(ctFrameSetter, CFRangeMake(0, 0), path, nil)
let lines = CTFrameGetLines(ctFrame) as Array
var lineOrigins = Array<CGPoint>(count: lines.count, repeatedValue: CGPointZero)//獲取每一個行的坐標(biāo)
CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), &lineOrigins)
var lineAscent:CGFloat = 0
var lineDescent:CGFloat = 0
var lineLeading:CGFloat = 0
var lineTotalHeight:CGFloat = 0
for (_,line) in lines.enumerate() {
CTLineGetTypographicBounds(line as! CTLine, &lineAscent, &lineDescent, &lineLeading)
let oneLineHeight = lineAscent+lineDescent + lineLeading//這里可以接上細(xì)節(jié)微調(diào)豌习，來返回高度
lineTotalHeight += oneLineHeight
}
//高度就這么計算好了
return lineTotalHeight
}
CTLineDraw繪制肥隆，就是將CTFrameDraw拆分而已
override func drawInContext(ctx: CGContext) {
super.drawInContext(ctx)
//坐標(biāo)系轉(zhuǎn)換
CGContextSetTextMatrix(ctx, CGAffineTransformIdentity)
CGContextTranslateCTM(ctx, 0, self.bounds.size.height)
CGContextScaleCTM(ctx, 1.0, -1.0)
//創(chuàng)建繪制的區(qū)域
let path = CGPathCreateMutable()
CGPathAddRect(path, nil, self.bounds)
// 4.創(chuàng)建需要繪制的文字
let attributed = NSMutableAttributedString(string: "估后共和國開不開vbdkaph估后共和國開不開vbdkaph??????????????????????????????????????????????????????????????這是我的第一個coreText demo，我是要給兵來自老白干I型那個餓哦個呢給個I類回滾igkhpwfh 評估后共和國開不開vbdkaphphohghg 的分工額好幾個遼寧省更怕hi維護(hù)你不看hi好人佛【井柏然把餓哦個?");
attributed.addAttribute(NSFontAttributeName, value: UIFont.systemFontOfSize(20), range: NSMakeRange(0, 5));
attributed.addAttribute(NSForegroundColorAttributeName, value: UIColor.redColor(), range: NSMakeRange(3, 10));
attributed.addAttribute(NSForegroundColorAttributeName, value: UIColor.orangeColor(), range: NSMakeRange(0, 2));
//創(chuàng)建段落屬性
let paraStyle = NSMutableParagraphStyle()
attributed.addAttribute(NSParagraphStyleAttributeName, value: paraStyle, range: NSMakeRange(0, attributed.length))
//根據(jù)計算的高度畫一個比邊框 start
let strockeHegith = self.getDisplayHeight(attributed, width: ScreenWidth)
CGContextSaveGState(ctx)
CGContextSetTextMatrix(ctx, CGAffineTransformIdentity)
CGContextTranslateCTM(ctx, 0, self.bounds.size.height)
CGContextScaleCTM(ctx, 1.0, -1.0)
let strokePath = CGPathCreateMutable()
CGPathAddRect(strokePath, nil, CGRect(x: 1, y: 1, width: ScreenWidth-2, height: strockeHegith))
CGContextAddPath(ctx, strokePath)
CGContextSetStrokeColorWithColor(ctx, UIColor.purpleColor().CGColor)
CGContextStrokePath(ctx)
CGContextRestoreGState(ctx)
//根據(jù)計算的高度畫一個比邊框 end
let ctFrameSetter = CTFramesetterCreateWithAttributedString(attributed)
let ctFrame = CTFramesetterCreateFrame(ctFrameSetter, CFRangeMake(0, attributed.length), path, nil)
let lines = CTFrameGetLines(ctFrame) as NSArray
var originsArray = Array<CGPoint>(count: lines.count, repeatedValue: CGPointZero)//用于存儲每一行的坐標(biāo)
CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), &originsArray)
var frameY:CGFloat = 0
let kGlobalLineLeading:CGFloat = 0
for (i,line) in lines.enumerate() {
var lineAscent:CGFloat = 0
var lineDescent:CGFloat = 0
var lineLeading:CGFloat = 0
CTLineGetTypographicBounds(line as! CTLine, &lineAscent, &lineDescent, &lineLeading)
var lineOrigin = originsArray[i];
if (i > 0)
{
frameY = frameY - kGlobalLineLeading - lineAscent;//減去一個行間距凿宾，再減去第二行初厚，字形的上部分 （循環(huán)）
lineOrigin.y = frameY;
} else
{
frameY = lineOrigin.y;
}
// 調(diào)整成所需要的坐標(biāo)
CGContextSetTextPosition(ctx, lineOrigin.x, lineOrigin.y);
CTLineDraw(line as! CTLine, ctx);
frameY = frameY - lineDescent//說明下這里，就是減去字形下面部分
}
}
效果圖如下
總結(jié)：因為有中文，英文和表情的存在蕾久，默認(rèn)情況下這三種的行高都是不等的，可以用上面的方法微調(diào)行高障簿，使其所有情況下都是等高的栅迄。
為所需顯示的最后一行添加省略號
步驟：
1.獲取所需操作行的range
2.獲取需要干掉字符的屬性
3.將獲取的屬性，添加給省略號屬性
4.剩下的字符串拼接上省略號
5.創(chuàng)建一個全新的CTLine繪制
6.繪制CTLine
mark:7.別傻傻的西篓，省略號在這里就是一個表示岂津，可以用是任何東西
//處理最后一行吮成，將最后一個字符干掉粱甫，并且加上省略號
let lCharacter = "……"
if i == lines.count - 1 {
let lastLineRange = CTLineGetStringRange(line as! CTLine)
let lastCharAttribute = attributed.attributesAtIndex(attributed.length - 1, effectiveRange: nil)
let lastAppentAttributeStr = NSAttributedString(string: lCharacter, attributes: lastCharAttribute)
let foreAttributeStr = attributed.attributedSubstringFromRange(NSMakeRange(lastLineRange.location, lastLineRange.length - 2)) as! NSMutableAttributedString//這里減去2是因為后面有個結(jié)尾的符號茶宵，c語言里面的“/n”
let afterAttributeStr = attributed.attributedSubstringFromRange(NSMakeRange(lastLineRange.location + lastLineRange.length - 1, 1)) as! NSMutableAttributedString
print("after:\\(afterAttributeStr.string)測試")
foreAttributeStr.appendAttributedString(lastAppentAttributeStr)
let createLastline = CTLineCreateWithAttributedString(foreAttributeStr)
CTLineDraw(createLastline, ctx)
}else{
CTLineDraw(line as! CTLine, ctx)
}
