UIBezierPath开发杂谈

以几个例子来说明UIBezierPath的使用。

1.

UIBezierPath *aPath = [UIBezierPath bezierPath];

// Set the starting point of the shape.

[aPath moveToPoint:CGPointMake(100.0, 0.0)];

// Draw the lines.

[aPath addLineToPoint:CGPointMake(200.0, 40.0)];

[aPath addLineToPoint:CGPointMake(160, 140)];

[aPath addLineToPoint:CGPointMake(40.0, 140)];

[aPath addLineToPoint:CGPointMake(0.0, 40.0)];

[aPath closePath];

moveToPoint:方法，移动到此位置开始。之后可以画线addLineToPoint：。

类似这个画多边形的使用，贝塞尔曲线可以用来画圆，椭圆，矩形。大家可以在文档里看到各个方法的使用。

2.

// Create the path data.

CGMutablePathRef cgPath = CGPathCreateMutable();

CGPathAddEllipseInRect(cgPath, NULL, CGRectMake(0, 0, 300, 300));

CGPathAddEllipseInRect(cgPath, NULL, CGRectMake(50, 50, 200, 200));

// Now create the UIBezierPath object.

UIBezierPath *aPath = [UIBezierPath bezierPath];

aPath.CGPath = cgPath;

aPath.usesEvenOddFillRule = YES;

// After assigning it to the UIBezierPath object, you can release

// your CGPathRef data type safely.

CGPathRelease(cgPath);

UIBezierPath就是一个对CGPathRef数据的包装。可以直接对CGPathRef数据处理，并赋值给UIBezierPath对象。

3.

- (void)drawRect:(CGRect)rect

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// Create an oval shape to draw.

UIBezierPath *aPath = [UIBezierPath bezierPathWithOvalInRect:

CGRectMake(0, 0, 200, 100)];

// Set the render colors.

[[UIColor blackColor] setStroke];

 [[UIColor redColor] setFill];

CGContextRef aRef = UIGraphicsGetCurrentContext();

// If you have content to draw after the shape,

// save the current state before changing the transform.

//CGContextSaveGState(aRef);

// Adjust the view's origin temporarily. The oval is

// now drawn relative to the new origin point.

CGContextTranslateCTM(aRef, 50, 50);

// Adjust the drawing options as needed.

aPath.lineWidth = 5;

// Fill the path before stroking it so that the fill

// color does not obscure the stroked line.

[aPath fill];

[aPath stroke];

// Restore the graphics state before drawing any other content.

//CGContextRestoreGState(aRef);

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以上就是把贝塞尔曲线展示出来的方法。

其中UIGraphicsGetCurrentContext（）方法是用来获取当前的上下文。

CGContextTranslateCTM（）方法用来做变换矩阵。

CGContextSaveGState和

CGContextRestoreGState方法用来保存和恢复当前的上下文，不受矩阵变换影响。

4.另外可以捕获贝塞尔曲线范围内的点击事件并做处理。

具体可以通过containsPoint: 方法。

5.另外，贝塞尔曲线还可以不在drawRect方法中使用。配合视图层，可以把贝塞尔曲线画出来。示例如下所示。

UIBezierPath * backStrokePath = [UIBezierPath bezierPath];

    backStrokePath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.frame.size.width/2, self.frame.size.height/2) radius:_object.radiousFlt startAngle:0 endAngle:M_PI*2 clockwise:YES];

//画线

    CAShapeLayer *backStrokeShapeLayer = [[CAShapeLayer layer] retain];

    backStrokeShapeLayer.path = backStrokePath.CGPath;

    backStrokeShapeLayer.fillColor = [CommonTools colorWithHexString:_object.backColorStr].CGColor;

    [self.layer addSublayer:backStrokeShapeLayer];

    [backStrokeShapeLayer release];