Stephen Laughton Stephen Laughton - 1 month ago 12
Ruby Question

RubyMotion Pie Chart CALayer

I am trying to translate this example http://lepetit-prince.net/ios/?p=1510 into RubyMotion and neither of the 'pie slices' I create show up on screen. I am not using the for loop in the example because I am only using two 'slices' of the pie. Any ideas?

chart = UIView.alloc.initWithFrame(CGRect.new([60, 100], [200, 200]))
chart.backgroundColor = UIColor.colorWithRed(0, green:0, blue:0, alpha:0.5)
chart.layer.cornerRadius = 100
@window.addSubview(chart)

green = 70.0
red = 30.0

red = red / 100.0 * 2.0 * Math::PI
green = green / 100 * 2.0 * Math::PI
start = 0.0

path = UIBezierPath.alloc.init
finish = start + red
sa = start - Math::PI / 2.0
ea = finish - Math::PI / 2.0
puts sa, ea
path.moveToPoint(CGPoint.new(100, 100))
path.addArcWithCenter(CGPoint.new(100, 100), radius:100, startAngle:sa, endAngle:ea, clockwise:true)
sl = CAShapeLayer.alloc.init
sl.fillColor = UIColor.redColor
sl.path = path.CGPath
chart.layer.addSublayer(sl)

start = finish

path = UIBezierPath.alloc.init
finish = start + green
sa = start - Math::PI / 2.0
ea = finish - Math::PI / 2.0
path.moveToPoint(CGPoint.new(100, 100))
path.addArcWithCenter(CGPoint.new(100, 100), radius:100, startAngle:sa, endAngle:ea, clockwise:true)
sl = CAShapeLayer.alloc.init
sl.fillColor = UIColor.greenColor
sl.path = path.CGPath
chart.layer.addSublayer(sl)

mask = UIView.alloc.initWithFrame(CGRect.new([0, 0], [196, 196]))
mask.layer.cornerRadius = 98
mask.center = CGPoint.new(100, 100)
mask.backgroundColor = UIColor.whiteColor

chart.addSubview(mask)

Answer

I got your code to work with minor modifications.

  1. The only real bug was that the fill color of a CALayer needs to be a CGColor and not a UIColor. To fix that, I added .CGColor to do the conversion.

  2. I put your code inside of viewDidLoad of a ViewController. Since you didn't provide all of your code, I wasn't sure how you had implemented it.

  3. It isn't necessary to use CGPoint.new and CGRect.new in RubyMotion. I replaced those with simpler direct array constants, such as [100, 100] and [[60, 100], [200, 200]].

  4. I made the mask smaller so that it looked more like the original example.

Here's the full code:

app_delegate.rb

class AppDelegate
  def application(application, didFinishLaunchingWithOptions:launchOptions)
    @window = UIWindow.alloc.initWithFrame(UIScreen.mainScreen.bounds)
    @window.rootViewController = ViewController.alloc.init
    @window.makeKeyAndVisible
    true
  end
end

view_controller.rb

class ViewController < UIViewController
  def viewDidLoad
    view.backgroundColor = UIColor.whiteColor

    chart = UIView.alloc.initWithFrame([[60, 100], [200, 200]])
    chart.backgroundColor = UIColor.colorWithRed(0, green:0, blue:0, alpha:0.5)
    chart.layer.cornerRadius = 100

    green = 70.0
    red = 30.0

    red = red / 100.0 * 2.0 * Math::PI
    green = green / 100 * 2.0 * Math::PI
    start = 0.0

    path = UIBezierPath.alloc.init
    finish = start + red
    sa = start - Math::PI / 2.0
    ea = finish - Math::PI / 2.0
    puts sa, ea
    path.moveToPoint([100, 100])
    path.addArcWithCenter([100, 100], radius:100, startAngle:sa, endAngle:ea, clockwise:true)
    sl = CAShapeLayer.alloc.init
    sl.fillColor = UIColor.redColor.CGColor
    sl.path = path.CGPath
    chart.layer.addSublayer(sl)

    start = finish

    path = UIBezierPath.alloc.init
    finish = start + green
    sa = start - Math::PI / 2.0
    ea = finish - Math::PI / 2.0
    path.moveToPoint([100, 100])
    path.addArcWithCenter([100, 100], radius:100, startAngle:sa, endAngle:ea, clockwise:true)
    sl = CAShapeLayer.alloc.init
    sl.fillColor = UIColor.greenColor.CGColor
    sl.path = path.CGPath
    chart.layer.addSublayer(sl)

    mask = UIView.alloc.initWithFrame([[0, 0], [100, 100]])
    mask.layer.cornerRadius = 50 
    mask.center = [100, 100]
    mask.backgroundColor = UIColor.whiteColor

    chart.addSubview(mask)
    view.addSubview(chart)
  end
end