调用drawViewHierarchyInRect时如何防止闪存：afterScreenUpdates：在iOS 8？

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

导致1帧闪光的图像.您可以在屏幕上看到它一秒钟.只有当AfterScreenUpdates参数为YES时才会发生.

这是我完整的截图代码：

UIGraphicsBeginImageContextWithOptions(self.bounds.size,NO,sf);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSaveGState(ctx);
CGContextConcatCTM(ctx,[self.layer affineTransform]);

if ([self respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)]) { // iOS 7+
    [self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];
} else { // iOS 6
    [self.layer renderInContext:ctx];
}

UIImage *image = UIGraphicsGetimageFromCurrentimageContext();

CGContextRestoreGState(ctx);
UIGraphicsEndImageContext();

有解决方法吗？