一、如果是自定義一個(gè)繼承于UIView的子類要在這個(gè)子類view上畫圖的話：1.假如是在drawRect：方法中單純地畫貝塞爾曲線?

- (void)set;

- (void)setFill;

- (void)setStroke;

這三個(gè)方法是用來(lái)設(shè)置這種畫線方式所需的邊色或者填充色（是類UIColor的實(shí)例方法）UIBezierPath *path = [UIBezierPath bezierPath];

[path stroke];//這個(gè)方法必須要寫的,否則不會(huì)畫出來(lái)（描邊）

[path fill];//這個(gè)也要寫，否則不會(huì)畫線（填充）

2.假如畫完線之后（不論是否在drawRect：方法中），所畫貝塞爾曲線的CGPath屬性是用作CAShapeLayer的path屬性的那么[path stroke]、[path fill]這兩個(gè)方法可以不要，（1）如果非要寫的話畫線的代碼需要放到

UIGraphicsBeginImageContext(self.view.bounds.size);

UIGraphicsEndImageContext();

這兩句代碼之間才能避免控制臺(tái)打印出一串

“Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextSaveGState: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextSetLineWidth: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextSetLineJoin: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextSetLineCap: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextSetMiterLimit: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextSetFlatness: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextAddPath: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextDrawPath: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

Jul? 6 14:32:00? TextBeiSaiEr[7433]: CGContextRestoreGState: invalid context 0x0. If you want to see the backtrace, please set CG_CONTEXT_SHOW_BACKTRACE environmental variable.

”

這些警告。

如果在這兩句代碼之間用

CGContextRef contextRef =UIGraphicsGetCurrentContext();

CGContextAddEllipseInRect(contextRef, CGRectMake(0,0,100,100));

CGContextSetFillColorWithColor(contextRef,? [UIColor blueColor].CGColor);

?CGContextFillPath(contextRef);

來(lái)畫線的話，下面這句代碼是必須的

UIImage* image = UIGraphicsGetImageFromCurrentImageContext();

（2）如果不寫[path stroke]、[path fill]這兩個(gè)方法的話

UIGraphicsBeginImageContext(self.view.bounds.size);

UIGraphicsEndImageContext();

這兩句代碼也可以不需要

二、如果不自定義UIView的子類

可以直接按一中的第2點(diǎn)來(lái)處理

代碼如下：（寫在viewDidLoad方法中的）

UIBezierPath* path = [UIBezierPath bezierPath];

path.lineWidth =3.0;

path.lineCapStyle =kCGLineCapRound;//終點(diǎn)樣式

path.lineJoinStyle =kCGLineJoinRound;//連接點(diǎn)樣式

[path moveToPoint:CGPointMake(100,20)];//起點(diǎn)

[path addLineToPoint:CGPointMake(200,40)];//途經(jīng)點(diǎn)

[path addLineToPoint:CGPointMake(160,140)];//途經(jīng)點(diǎn)

[path addLineToPoint:CGPointMake(40,140)];//途經(jīng)點(diǎn)

[path addLineToPoint:CGPointMake(0,40)];//途經(jīng)點(diǎn)

[path closePath];//閉合

CAShapeLayer * layer = [CAShapeLayer layer];

layer.path = path.CGPath;

layer.backgroundColor = [UIColor clearColor].CGColor;

layer.fillColor = [UIColor clearColor].CGColor;

layer.lineCap =kCALineCapRound;

layer.lineJoin =kCALineJoinRound;

layer.strokeColor = [UIColor redColor].CGColor;

layer.lineWidth = path.lineWidth;

self.view.layer.shouldRasterize = YES;//去線條鋸齒

[self.view.layer addSublayer:layer];