核心函数是:CGContextAddArc(CGContextRef c, CGFloat x, CGFloat y, CGFloat radius, CGFloat startAngle, CGFloat endAngle, int clockwise)
* CGContextRef: 图形上下文
* x,y: 开始画的坐标
* radius: 半径
* startAngle, endAngle: 开始的弧度,结束的弧度
* clockwise: 画的方向(顺时针,逆时针)
有了这个函数可以画出任意扇形,所以饼图也不再话下.
#define PI 3.14159265358979323846
#define radius 100
static inline float radians(double degrees) {
return degrees * PI / 180;
}
static inline void drawArc(CGContextRef ctx, CGPoint point, float angle_start, float angle_end, UIColor* color) {
CGContextMoveToPoint(ctx, point.x, point.y);
CGContextSetFillColor(ctx, CGColorGetComponents( [color CGColor]));
CGContextAddArc(ctx, point.x, point.y, radius, angle_start, angle_end, 0);
//CGContextClosePath(ctx);
CGContextFillPath(ctx);
}
- (void)drawRect:(CGRect)rect {
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextClearRect(ctx, rect);
float angle_start = radians(0.0);
float angle_end = radians(121.0);
drawArc(ctx, self.center, angle_start, angle_end, [UIColor yellowColor]);
angle_start = angle_end;
angle_end = radians(228.0);
drawArc(ctx, self.center, angle_start, angle_end, [UIColor greenColor]);
angle_start = angle_end;
angle_end = radians(260);
drawArc(ctx, self.center, angle_start, angle_end, [UIColor orangeColor]);
angle_start = angle_end;
angle_end = radians(360);
drawArc(ctx, self.center, angle_start, angle_end, [UIColor purpleColor]);
}