原文：http://www.cnblogs.com/rollrock/p/3832997.html?utm_source=tuicool
#define DegreesToRadians(_degrees)? ? ? ((M_PI * (_degrees))/180) //此處是我自己補(bǔ)充的宏定義询兴，重要參數(shù)
CGRect rect =? CGRectMake( 100,? 100,? 100,? 100);
UIView * bgView = [[ UIView? alloc] initWithFrame:rect];
bgView.backgroundColor? = [UIColor? grayColor ];
[ self. view? addSubview:bgView];
CAShapeLayer * trackLayer = [ CAShapeLayer? layer];
trackLayer. frame = bgView. bounds;
[bgView. layer? addSublayer:trackLayer];
trackLayer. fillColor = [[ UIColor? clearColor]? CGColor];//填充顏色
trackLayer. strokeColor = [[ UIColor? redColor]? CGColor];//邊框顏色
trackLayer. opacity =? 0.5;
trackLayer.lineCap? = kCALineCapRound ;
trackLayer. lineWidth =? 4.0;? // 紅色的邊框?qū)挾?/p>
UIBezierPath? * path = [ UIBezierPath? bezierPathWithArcCenter :CGPointMake ( 50 ,? 50 ) radius : 48? startAngle : DegreesToRadians (- 210 ) endAngle : DegreesToRadians ( 30 ) clockwise : YES ];
//角度是從 -210到30度叮雳，具體可以看如下圖所示
trackLayer. path = [path? CGPath];
運(yùn)行結(jié)果如下圖：
基于以上的代碼拯杠，下面添加漸變的效果
CALayer * gradinetLayer = [ CALayer? layer];
CAGradientLayer? * gradLayer1 = [CAGradientLayer? layer ];
gradLayer1. frame =? CGRectMake( 0,? 0, bgView. frame. size. width/ 2, bgView. frame. size. height);
[gradLayer1 setColors :[ NSArray? arrayWithObjects :( id )[[ UIColor? redColor ] CGColor ],( id )[ UIColorFromRGB ( 0xfde802 ) CGColor ],? nil ]];
[gradLayer1 setLocations: @[@0.5, @0.9, @1? ]];
[gradLayer1 setStartPoint :CGPointMake ( 0.5 ,? 1 )];
[gradLayer1 setEndPoint: CGPointMake( 0.5,? 0)];
[gradinetLayer addSublayer:gradLayer1];
CAGradientLayer? * gradLayer2 = [CAGradientLayer? layer ];
gradLayer2. frame =? CGRectMake(bgView. frame. size. width/ 2,? 0, bgView. frame. size. width/ 2, bgView. frame. size. height);
[gradLayer2 setColors :[ NSArray? arrayWithObjects :( id )[ UIColorFromRGB ( 0xfde802 ) CGColor ],( id )[[ UIColor? blueColor ] CGColor ],? nil ]];
[gradLayer2 setStartPoint :CGPointMake ( 0.5 ,? 0 )];
[gradLayer2 setEndPoint: CGPointMake( 0.5,? 1)];
[gradinetLayer addSublayer:gradLayer2];
//[gradinetLayer setMask:trackLayer];
[bgView. layer? addSublayer:gradinetLayer];
本文轉(zhuǎn)自 張江論壇? ? 轉(zhuǎn)載請(qǐng)注明 http://www.999dh.net/home.php?mod=space&uid=1&do=blog&quickforward=1&id=328
以上的代碼運(yùn)行后得到的結(jié)果如下：
解釋如下：
setLocations? 理論上來(lái)說(shuō)酥夭，是設(shè)置 colors的顯示區(qū)域的（這里還未弄清楚原理）
setStartPoint 是顏色的開(kāi)始漸變的開(kāi)始點(diǎn)哟绊，默認(rèn)的是(0,0)也就是左上角
setEndPoint 是顏色的停止?jié)u變的點(diǎn)，默認(rèn)的是(1,1)
如果按默認(rèn)的來(lái)，gradLayer1 的顏色漸變應(yīng)該是從左上角由redcolor漸變到右下角（顏色為 0xfde802)
而代碼中設(shè)置的 startPoint為（0.5，1）锌订，指的是在x軸中間，y軸底部画株；endPoint為（0.5辆飘，0）指的是在x軸中間，y軸頂部谓传。
最后將代碼[gradinetLayer setMask:trackLayer]; 注釋去掉蜈项，得到如下的運(yùn)行結(jié)果
這里主要的作用就是 setMask的功勞，但是為什么trackLayer的strokeColor沒(méi)有生效续挟，這里也不是很清楚紧卒。（哎，不懂的太多了哎诗祸，確實(shí)太多）
