iOS8的iPad环境下打不开相册或者拍照

但是在iOS8的iPad环境下，却打不开相册或者拍照，提示如下：

Warning: Attempt to present <UIImagePickerController: 0x7fb3d1167a00>  on <CubeWebViewController: 0x7fb3d324ad20>which is already presenting (null)

解决方法如下:

[[NSOperationQueue mainQueue] addOperationWithBlock:^{                UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:picker];                self.popoverController = popover;                [self.popoverController presentPopoverFromRect:CGRectMake(0, 0, 600, 800) inView:self.viewController.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];            }];

在pop的地方加上 

 [[NSOperationQueuemainQueue] addOperationWithBlock:^{

 //code...

}];