iphone上如何绘制饼图（使用CGContextAddArc）

CGContextAddArc是一个比较强大的函数，建议仔细看一下iphone的开发文档。

CGContextAddArc(CGContextRef c, CGFloat x, CGFloat y, CGFloat radius, CGFloat startAngle, CGFloat endAngle, intclockwise)

 

• 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)

1 <pre class="brush:objc">GraphView.h文件：</pre>

 

1 #import <UIKit/UIKit.h>
2 #import <Foundation/Foundation.h>
3
4 @interface GraphView : UIView {
5
6 }
7
8 @end

 

 

 

01	<pre class="brush:objc">GraphView.m文件：</pre>

02	<pre class="brush:objc"><div class="cnblogs_Highlighter"><pre class="brush:objc">#import "GraphView.h"

03	#define PI 3.14159265358979323846

04	static inline float radians(double degrees) { return degrees * PI / 180; }

05

06

07	@interface GraphView(private)

08	//如果有什么私有方法，在这里声明

09

@end

10

11	@implementation GraphView

12

13	- (id)initWithFrame:(CGRect)frame {

14	if ((self = [super initWithFrame:frame])) {

15	// Initialization code

16

}

17	return self;

18

}

19

20	- (void)drawRect:(CGRect)rect {

21

22	CGRect parentViewBounds = self.bounds;

23	CGFloat x = CGRectGetWidth(parentViewBounds)/2;

24	CGFloat y = CGRectGetHeight(parentViewBounds)*0.55;

25

26	// Get the graphics context and clear it

27	CGContextRef ctx = UIGraphicsGetCurrentContext();

28	CGContextClearRect(ctx, rect);

29

30	// define stroke color

31	CGContextSetRGBStrokeColor(ctx, 1, 1, 1, 1.0);

32

33	// define line width

34	CGContextSetLineWidth(ctx, 4.0);

35

36

37	// need some values to draw pie charts

38

39	double snapshotCapacity =20;

40	double rawCapacity = 100;

41	double systemCapacity = 1;

42

43	int offset = 5;

44	double pie1_start = 315.0;

45	double pie1_finish = snapshotCapacity *360.0/rawCapacity;

46	double system_finish = systemCapacity*360.0/rawCapacity;

47

48	CGContextSetFillColor(ctx, CGColorGetComponents( [[UIColor greenColor] CGColor]));

49	CGContextMoveToPoint(ctx, x+2*offset, y);

50	CGContextAddArc(ctx, x+2*offset, y, 100,  radians(snapshot_start), radians(snapshot_start+snapshot_finish), 0);

51	CGContextClosePath(ctx);

52	CGContextFillPath(ctx);

53

54	// system capacity

55	CGContextSetFillColor(ctx, CGColorGetComponents( [[UIColor colorWithRed:15 green:165/255 blue:0 alpha:1 ] CGColor]));

56	CGContextMoveToPoint(ctx, x+offset,y);

57	CGContextAddArc(ctx, x+offset, y, 100,  radians(snapshot_start+snapshot_finish+offset), radians(snapshot_start+snapshot_finish+system_finish), 0);

58	CGContextClosePath(ctx);

59	CGContextFillPath(ctx);

60

61	/* data capacity */

62	CGContextSetFillColor(ctx, CGColorGetComponents( [[UIColor colorWithRed:99/255 green:184/255 blue:255/255 alpha:1 ] CGColor]));

63	CGContextMoveToPoint(ctx, x, y);

64	CGContextAddArc(ctx, x, y, 100,  radians(snapshot_start+snapshot_finish+system_finish+offset), radians(snapshot_start), 0);

65	CGContextClosePath(ctx);

66	CGContextFillPath(ctx);

67

}

68

69

70	- (void)dealloc {

71	[super dealloc];

72

}

73

@end

74

75

</pre>

76

</div>

77	<br></pre>

78	<pre class="brush:objc"><br></pre>

79	<pre class="brush:objc">调用代码如下：</pre>

80	<pre class="brush:objc"><pre class="brush:objc">GraphView* viewTest = [[GraphView alloc] initWithFrame:CGRectMake(x,y,width,height)];</pre>

81	<pre class="brush:objc">[self.view addsubView:viewTest];</pre>

82	<pre class="brush:objc">[viewTest release];</pre>

83	<pre class="brush:objc"><br></pre>

84	<pre class="brush:objc"><br></pre>

85	<pre class="brush:objc">效果图如下：</pre>

86	<pre class="brush:objc"><img src="http://pic002.cnblogs.com/images/2010/169783/2010101900291074.png" alt=""><br></pre>

http://www.cnblogs.com/moshengren/archive/2010/10/19/1855246.html