How to display Text on a PieChart?

Question

I have Created a PieChart Using the following Code. Here, I Have taken the sum of x and y as 100% to display the x% as red color and y% as green color on pieChart.

On the red color i want to display the exact x% (Example 45% (or) 55%) and on the green color i want to display the exact y% (Example 55% (or) 45%).

In my application the X and Y values are Variables. Those Values are changing each time when i run my application. I want to display the pieChart with green and red colors with the percentage on those regions. How Can i make frames to display percentages on that regions?

.m file

- (void)drawRect:(CGRect)rect
{
// Drawing code

 int x = 25;
 int y = 42;

 float sum = x + y;
 float mult = (360/sum);

 float startDeg = 0;
 float endDeg = 0;

 int x = 74;
 int y = 60;
 int r = 60;

 CGContextRef ctx = UIGraphicsGetCurrentContext();
 CGContextSetRGBStrokeColor(ctx, 1.0, 1.0, 1.0, 1.0);
 CGContextSetLineWidth(ctx, 2.0);

 startDeg = 0;
 endDeg = (x * mult);
 if(startDeg != endDeg)
 {
 CGContextSetRGBFillColor(ctx, 0.0, 0.8, 0.0, 1.0);
 CGContextMoveToPoint(ctx, x, y);
 CGContextAddArc(ctx, x, y, r, (startDeg)*M_PI/180.0, (endDeg)*M_PI/180.0, 0);
 CGContextClosePath(ctx);
 CGContextFillPath(ctx);
 }

 startDeg = endDeg;
 endDeg = endDeg + (y * mult);
 if(startDeg != endDeg)
 {
 CGContextSetRGBFillColor(ctx, 0.8, 0.0, 0.0, 1.0);
 CGContextMoveToPoint(ctx, x, y);
 CGContextAddArc(ctx, x, y, r, (startDeg)*M_PI/180.0, (endDeg)*M_PI/180.0, 0);
 CGContextClosePath(ctx);
 CGContextFillPath(ctx);
 }
}

Answer 1

You can draw a string with NSString drawInRect during the drawRect method. For example:

[percentageString drawInRect:CGRectMake(100, 100, 30, 20) 
                    withFont:font 
               lineBreakMode:UILineBreakModeClip 
                   alignment:UITextAlignmentLeft];

Update

Here is how to find the x, y for placing text:

CGFloat startDegree = 180;                             // start at 180
CGFloat endDegree = degree;                            // end at some value

CGFloat mid = (endDegree + startDegree) / 2;           // find midpoint
CGFloat rad = DEGREES_TO_RADIANS(mid);                 // convert to radians


// center is center of pie chart
// radius is how big the pie chart is
// 30 is extra to draw text outside circle

CGFloat x =  center.x + ((radius + 30) * cos(rad));    
CGFloat y = center.y + ((radius + 30) * sin(rad));

NSLog(@"X Y: %f %f %f", x, y, degree);

NSString *text = @"Test";   
[text drawInRect:CGRectMake(x, y, 50, 44) withFont:[UIFont systemFontOfSize:14.0f]];

I had a sample pie chart so I used that. It has a slider with degrees. In the example, I can draw a segment of the pie chart from 180 degrees to 360 degrees.