Howto: Drawing Pie Charts using iPhone SDK

From rajeev karamchedu

Drawing Pie Charts using iPhone SDK

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.
An example of the pie charts the code base generates is below (a screenshot):

And now, for the code:

GraphView.h

# #(nothing to see here) # #import <UIKit/UIKit.h> #import <Foundation/Foundation.h> @interface GraphView : UIView { } @end

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); }