Ios drawViewHierarchyInRect打印全黑图像

我有一个我正试图打印的网页视图，当我加载一个很长（超过一页）的网页时，它会打印成黑色。我无法使用RenderContext方法，因为当我尝试打印页面时，由于内存问题，它会使应用程序崩溃。我正在使用dymo收据打印机

这是我的代码

+ (UIImage*)viewToImage:(UIView*)theView
{
    UIImage *image = nil;

    // Save current bounds so we can reset them laster
    CGRect tmpFrame = theView.frame;
    CGRect tmpBounds = theView.bounds;

    // Adjust the bounds of the webview so we can take a screen shot of the entire view, even if its scrolled off screen.
    CGRect aFrame = theView.bounds;
    aFrame.size.width = theView.frame.size.width;
    aFrame.size.height = theView.frame.size.height;
    theView.frame = aFrame;
    aFrame.size.height = [theView sizeThatFits:[[UIScreen mainScreen] bounds].size].height;
    theView.frame = aFrame;


    UIGraphicsBeginImageContextWithOptions(theView.bounds.size, NO, 1.8);

    [theView drawViewHierarchyInRect:theView.bounds afterScreenUpdates:YES];

    // crashes the app [self.layer renderInContext:UIGraphicsGetCurrentContext()];

    image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}