CPTPieChart打印空白

Question

尝试使用CorePlot的CPTPieChart并将其打印到打印机

CPTGraphHostingView *view  = [[CPTGraphHostingView alloc] initWithFrame:CGRectMake(10, 10, 600, 600)];
CPTXYGraph *printgraph     = [[CPTXYGraph          alloc] initWithFrame:CGRectMake(10, 10, 600, 600)];
view.printRect             = CGRectMake(10, 10, 600, 600);
view.hostedGraph           = printgraph;
printgraph.axisSet         = nil;
printgraph.delegate        = self;
printgraph.title           = @"Client Statistics";
printgraph.plotAreaFrame.masksToBorder = NO;

// Prepare a radial overlay gradient for shading/gloss
CPTGradient *overlayGradient = [[CPTGradient alloc] init];
overlayGradient.gradientType = CPTGradientTypeRadial;
overlayGradient = [overlayGradient addColorStop:[[CPTColor blackColor] colorWithAlphaComponent:0.0] atPosition:0.0];
overlayGradient = [overlayGradient addColorStop:[[CPTColor blackColor] colorWithAlphaComponent:0.2] atPosition:0.9];
overlayGradient = [overlayGradient addColorStop:[[CPTColor blackColor] colorWithAlphaComponent:0.5] atPosition:1.0];

CPTPieChart *pie   = [[CPTPieChart alloc] init];
pie.dataSource     = self;
pie.delegate       = self;
pie.pieRadius      = 190;
pie.startAngle     = M_PI_4;
pie.labelRotation  = 0;
pie.labelOffset    = -30.0;
pie.sliceDirection = CPTPieDirectionClockwise;
pie.overlayFill    = [CPTFill fillWithGradient:overlayGradient];
pie.labelRotationRelativeToRadius        = NO;
[printgraph addPlot:pie];
[printgraph  reloadData];

.... ....

 printOp = [NSPrintOperation printOperationWithView:view printInfo:printInfo];
[printOp runOperation];

标题显示在“打印预览”窗口中，但实际饼图为空白 如果我将视图添加到self.window.contentView，我可以看到饼图，以便正确构建和显示，但不打印？

任何想法 提前致谢