Here’s one way to draw a PIE chart using the latest iPhone SDK. There are a ton of tutorials out there that let you get started with the iPhone app development itself and I am by no means any authoritative source on learning how to develop one. Having said that, here’s a class file that will help you use the UIKit and Quartz to draw vector graphics.
GraphView.h
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#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
@interface GraphView : UIView {
}
@end
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GraphView.m
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#import "GraphView.h"
#define PI 3.14159265358979323846
static inline float radians(double degrees) { return degrees * PI / 180; }
@implementation GraphView
- (void)drawRect:(CGRect)rect {
CGRect parentViewBounds = self.bounds;
CGFloat x = CGRectGetWidth(parentViewBounds)/2;
CGFloat y = CGRectGetHeight(parentViewBounds)*0.55;
// Get the graphics context and clear it
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextClearRect(ctx, rect);
// define stroke color
CGContextSetRGBStrokeColor(ctx, 1, 1, 1, 1.0);
// define line width
CGContextSetLineWidth(ctx, 4.0);
// need some values to draw pie charts
double snapshotCapacity =20;
double rawCapacity = 100;
double systemCapacity = 1;
int offset = 5;
double pie1_start = 315.0;
double pie1_finish = snapshotCapacity *360.0/rawCapacity;
double system_finish = systemCapacity*360.0/rawCapacity;
CGContextSetFillColor(ctx, CGColorGetComponents( [[UIColor greenColor] CGColor]));
CGContextMoveToPoint(ctx, x+2*offset, y);
CGContextAddArc(ctx, x+2*offset, y, 100, radians(snapshot_start), radians(snapshot_start+snapshot_finish), 0);
CGContextClosePath(ctx);
CGContextFillPath(ctx);
// system capacity
CGContextSetFillColor(ctx, CGColorGetComponents( [[UIColor colorWithRed:15 green:165/255 blue:0 alpha:1 ] CGColor]));
CGContextMoveToPoint(ctx, x+offset,y);
CGContextAddArc(ctx, x+offset, y, 100, radians(snapshot_start+snapshot_finish+offset), radians(snapshot_start+snapshot_finish+system_finish), 0);
CGContextClosePath(ctx);
CGContextFillPath(ctx);
/* data capacity */
CGContextSetFillColor(ctx, CGColorGetComponents( [[UIColor colorWithRed:99/255 green:184/255 blue:255/255 alpha:1 ] CGColor]));
CGContextMoveToPoint(ctx, x, y);
CGContextAddArc(ctx, x, y, 100, radians(snapshot_start+snapshot_finish+system_finish+offset), radians(snapshot_start), 0);
CGContextClosePath(ctx);
CGContextFillPath(ctx);
}
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iOS Tutorial 