核心情节自定义主题？

我在 iPhone 应用程序中使用 Core-Plot 绘制趋势图，但尚未找到如何自定义背景。我可以使用内置主题创建主题，例如 kCPPlainWhiteTheme，但如何更改它们？或者创建一个新的？

我基本上需要做的就是使背景透明。

编辑/更新

我刚刚测试了这段代码，但它似乎不起作用：

    //CPTheme *theme = [CPTheme themeNamed:kCPPlainWhiteTheme];
    CPTheme *theme = [[CPTheme alloc]init];
    chartTrend5 = (CPXYGraph *)[theme newGraph];    
    chartView.hostedGraph = chartTrend5;
    chartTrend5.paddingLeft = 0.0;
    chartTrend5.paddingTop = 0.0;
    chartTrend5.paddingRight = 0.0;
    chartTrend5.paddingBottom = 0.0;
    chartTrend5.fill = nil;
    chartTrend5.borderLineStyle = nil;
    chartView.hostedGraph.fill = nil;

    chartTrend5PlotSpace = (CPXYPlotSpace *)chartTrend5.defaultPlotSpace;
    chartTrend5PlotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0)
                                                              length:CPDecimalFromFloat(5)];

    // range is 0-125, but since the frame heights is 90, 
    // we need to convert the points to this adjusted scale. The factor is 0.72 => (90/125)
    chartTrend5PlotSpace.yRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0)
                                                              length:CPDecimalFromFloat(90)];



    CPXYAxisSet *axisSet = (CPXYAxisSet *)chartTrend5.axisSet;

    CPXYAxis *x = axisSet.xAxis;
    x.majorIntervalLength =  CPDecimalFromFloat(100);
    //x.constantCoordinateValue = CPDecimalFromFloat(2);
    x.minorTicksPerInterval = 2;
    x.borderWidth = 0;
    x.labelExclusionRanges = [NSArray arrayWithObjects:
                              [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(-1) 
                                                          length:CPDecimalFromFloat(800)], 
                              nil];;

    CPXYAxis *y = axisSet.yAxis;
    y.majorIntervalLength = CPDecimalFromFloat(100);
    y.minorTicksPerInterval = 1;
    //y.constantCoordinateValue = length:CPDecimalFromFloat(2);
    y.labelExclusionRanges = [NSArray arrayWithObjects:
                              [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(-26) 
                                                          length:CPDecimalFromFloat(100)], 
                              nil];





    CPScatterPlot *dataSourceLinePlot = [[[CPScatterPlot alloc] init] autorelease];
    dataSourceLinePlot.identifier = @"TrendChart";
    dataSourceLinePlot.dataLineStyle.lineWidth = 2.f;
    dataSourceLinePlot.dataLineStyle.lineColor = [CPColor colorWithComponentRed:(16/255.f) 
                                                                          green:(101/255.f) 
                                                                           blue:(122/255.f) 
                                                                          alpha:1];
    dataSourceLinePlot.dataSource = self;
    [chartTrend5 addPlot:dataSourceLinePlot];
    chartTrend5.fill = nil;
    // Put an area gradient under the plot above

    CPColor *areaColor = [CPColor colorWithComponentRed:(212/255.f) 
                                                  green:(233/255.f)
                                                   blue:(216/255.f)
                                                  alpha:1];

    CPGradient *areaGradient = [CPGradient gradientWithBeginningColor:areaColor 
                                                          endingColor:areaColor];
    areaGradient.angle = -90.0f;
    CPFill *areaGradientFill = [CPFill fillWithGradient:areaGradient];
    dataSourceLinePlot.areaFill = areaGradientFill;
    dataSourceLinePlot.areaBaseValue = CPDecimalFromString(@"5.25");

这里我设置了 fill 属性CPXYGraph *图表趋势5 and *CPXYPlotSpace *chartTrend5PlotSpace to nil.

除了埃里克建议的之外，您还可以尝试将填充设置为透明颜色。例如，我过去曾使用它为图表提供透明背景：

CPTTheme *theme = [CPTTheme themeNamed:kCPPlainWhiteTheme];
graph = (CPTXYGraph *)[theme newGraph];

graph.fill = [CPTFill fillWithColor:[CPTColor clearColor]];
graph.plotAreaFrame.fill = [CPTFill fillWithColor:[CPTColor clearColor]];