Charts: Add gradient to bar chart

[gustavo-yy]

Hi, I'm trying to add a gradient to my bar charts but I can only draw the first bar:

I added the gradient at _BarChartRenderer->drawDataSet_ right after if _!isSingleColor{}_

let fillColors = [UIColor.white.cgColor, UIColor.yellow.cgColor]
let locations:[CGFloat] = [0.0, 1.0]

context.clip(to: barRect)
let gradient:CGGradient
let colorspace:CGColorSpace
colorspace = CGColorSpaceCreateDeviceRGB()

gradient = CGGradient(colorsSpace: colorspace, colors: fillColors as CFArray, locations: locations)!

//Vertical Gradient
let startPoint:CGPoint = CGPoint(x: 0.0, y: viewPortHandler.contentBottom)
let endPoint:CGPoint = CGPoint(x: 0.0, y: viewPortHandler.contentTop)

context.drawLinearGradient(gradient, start: startPoint, end: endPoint, options: .init(rawValue: 0))

[liuxuan30]

why can't you apply the code to other bars? What's the issue?

[gustavo-yy]

That's the problem, i don't know why it's only taking effect to the first bar, in the image i should have around 16 bars but it looks like the others are transparent

[liuxuan30]

how about you remove the gradient? All bars appear? Maybe better ask on SO...
Also maybe check the context state?

[gustavo-yy]

yes, if I remove the gradient all the bars appear normally

[gustavo-yy]

I've added an if(j==10){} to draw the gradient at the bar 11 and it looks like this:

I should have 28 bars but it stops at the 11 bar

[liuxuan30]

it looks like a CoreGraphics issue to me. Have you tried to save/clean the state every time you want to render a bar? I don't know the reason yet..

[liuxuan30]

BTW, I just came across https://github.com/danielgindi/Charts/issues/2515, when someone us using CALayer to draw gradient, and it works though.. CoreGraphics is underlying CALayer gradient so I guess you can refer something, or at least a work around.

[sokalyambda]

I played with save/restore gState as mentioned before and now it works!Hope, this will help someone, thank you guys.

if !isSingleColor
{
let fillColors = [dataSet.color(atIndex: 0).cgColor, dataSet.color(atIndex: 1).cgColor]
let locations:[CGFloat] = [0.0, 1.0]

            context.saveGState()
            context.clip(to: barRect)
            let gradient:CGGradient
            let colorspace:CGColorSpace
            colorspace = CGColorSpaceCreateDeviceRGB()

            gradient = CGGradient(colorsSpace: colorspace, colors: fillColors as CFArray, locations: locations)!

            //Vertical Gradient
            let startPoint:CGPoint = CGPoint(x: 0.0, y: viewPortHandler.contentBottom)
            let endPoint:CGPoint = CGPoint(x: 0.0, y: viewPortHandler.contentTop)

            context.drawLinearGradient(gradient, start: startPoint, end: endPoint, options: .init(rawValue: 0))
            context.restoreGState()
        } else {
            context.fill(barRect)
        }

[gustavo-yy]

@sokalyambda thank you, it works!

[alxarsnk]

@sokalyambda thx, it's really works