一、内置的渐变色 

1，使用样例

（1）AAInfographics 图表内置了一套渐变色（AAGradientColor）供我们直接使用，下面是柱状图使用渐变色的效果：

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 初始化图表视图控件
        let chartWidth  = self.view.frame.size.width
        let chartHeight = self.view.frame.size.height - 200
        let aaChartView = AAChartView()
        aaChartView.frame = CGRect(x:0, y:0, width:chartWidth, height:chartHeight)
        self.view.addSubview(aaChartView)
        
        // 初始化图表模型
        let chartModel = AAChartModel()
            .chartType(.column)//图表类型
            .title("城市天气变化")//图表主标题
            .subtitle("2020年09月18日")//图表副标题
            .inverted(false)//是否翻转图形
            .yAxisTitle("摄氏度")// Y 轴标题
            .legendEnabled(true)//是否启用图表的图例(图表底部的可点击的小圆点)
            .tooltipValueSuffix("摄氏度")//浮动提示框单位后缀
            .categories(["一月", "二月", "三月", "四月", "五月", "六月"])
            .colorsTheme([AAGradientColor.oceanBlue,
                          AAGradientColor.sanguine,
                          AAGradientColor.lusciousLime])//渐变颜色数组
            .series([
                AASeriesElement()
                    .name("东京")
                    .data([7.0, 6.9, 9.5, 14.5, 18.2, 21.5])
                    .toDic()!,
                AASeriesElement()
                    .name("纽约")
                    .data([0.2, 0.8, 5.7, 11.3, 17.0, 25.0])
                    .toDic()!,
                AASeriesElement()
                    .name("柏林")
                    .data([0.9, 0.6, 3.5, 8.4, 13.5, 17.0])
                    .toDic()!])
        
        // 图表视图对象调用图表模型对象,绘制最终图形
        aaChartView.aa_drawChartWithChartModel(chartModel)
    }
}

（2）下面是折线图使用渐变色的效果：

2，所有的渐变颜色

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let gradientColorNamesArr = [
            "oceanBlue",
            "sanguine",
            "lusciousLime",
            "purpleLake",
            "freshPapaya",
            "ultramarine",
            "pinkSugar",
            "lemonDrizzle",
            "victoriaPurple",
            "springGreens",
            "mysticMauve",
            "reflexSilver",
            "newLeaf",
            "cottonCandy",
            "pixieDust",
            "fizzyPeach",
            "sweetDream",
            "firebrick",
            "wroughtIron",
            "deepSea",
            "coastalBreeze",
            "eveningDelight",
            ]
        
        // 所有内置渐变色
        let gradientColorArr = [
            AAGradientColor.oceanBlue,
            AAGradientColor.sanguine,
            AAGradientColor.lusciousLime,
            AAGradientColor.purpleLake,
            AAGradientColor.freshPapaya,
            AAGradientColor.ultramarine,
            AAGradientColor.pinkSugar,
            AAGradientColor.lemonDrizzle,
            AAGradientColor.victoriaPurple,
            AAGradientColor.springGreens,
            AAGradientColor.mysticMauve,
            AAGradientColor.reflexSilver,
            AAGradientColor.newLeaf,
            AAGradientColor.cottonCandy,
            AAGradientColor.pixieDust,
            AAGradientColor.fizzyPeach,
            AAGradientColor.sweetDream,
            AAGradientColor.firebrick,
            AAGradientColor.wroughtIron,
            AAGradientColor.deepSea,
            AAGradientColor.coastalBreeze,
            AAGradientColor.eveningDelight,
            ]
        
        // 初始化图表视图控件
        let chartWidth  = self.view.frame.size.width
        let chartHeight = self.view.frame.size.height
        let aaChartView = AAChartView()
        aaChartView.frame = CGRect(x:0, y:0, width:chartWidth, height:chartHeight)
        self.view.addSubview(aaChartView)
        
        // 初始化图表模型
        let chartModel = AAChartModel()
            .chartType(.bar)//图表类型
            .title("城市天气变化")//图表主标题
            .inverted(false)//是否翻转图形
            .legendEnabled(true)//是否启用图表的图例(图表底部的可点击的小圆点)
            .tooltipValueSuffix("摄氏度")//浮动提示框单位后缀
            .categories(gradientColorNamesArr)
            .colorsTheme(gradientColorArr as [Any])//渐变颜色数组
            .series([
                AASeriesElement()
                    .name("2018")
                    .data(Array(0..<gradientColorArr.count).map{ _ in 75 })
                    .colorByPoint(true)
                    .toDic()!])
        
        // 图表视图对象调用图表模型对象,绘制最终图形
        aaChartView.aa_drawChartWithChartModel(chartModel)
    }
}

二、使用自定义的渐变颜色

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 初始化图表视图控件
        let chartWidth  = self.view.frame.size.width
        let chartHeight = self.view.frame.size.height - 200
        let aaChartView = AAChartView()
        aaChartView.frame = CGRect(x:0, y:0, width:chartWidth, height:chartHeight)
        self.view.addSubview(aaChartView)
        
        // 初始化图表模型
        let chartModel = AAChartModel()
            .chartType(.column)//图表类型
            .title("城市天气变化")//图表主标题
            .inverted(false)//是否翻转图形
            .legendEnabled(true)//是否启用图表的图例(图表底部的可点击的小圆点)
            .tooltipValueSuffix("摄氏度")//浮动提示框单位后缀
            .categories(["渐变1", "渐变3", "渐变2"])
            .colorsTheme([
                GradientColorDicMaker
                    .configureGradientColorDictionary(startColor: "000000",
                                                      endColor: "FFFFFF"),
                GradientColorDicMaker
                    .configureGradientColorDictionary(startColor: "FF00FF",
                                                      endColor: "FFFFFF"),
                GradientColorDicMaker
                    .configureGradientColorDictionary(startColor: "FF0000",
                                                      endColor: "FFFF00")
                ])//渐变颜色数组
            .series([
                AASeriesElement()
                    .name("2018")
                    .data(Array(0..<3).map{ _ in 75 })
                    .colorByPoint(true)
                    .toDic()!])
        
        // 图表视图对象调用图表模型对象,绘制最终图形
        aaChartView.aa_drawChartWithChartModel(chartModel)
    }
}