Taking a screenShot/Snapshot programmatically for iOS7 gives me an error

I am writing the code for capturing the screenShot of what I see on my screen when I press a button in Unity.

I am writing the following code :

ScreenCapture.h

#import <Foundation/Foundation.h>

#import <UIKit/UIKit.h>

#import "QuartzCore/QuartzCore.h"

@interface ScreenCaptureDelegate : UIViewController {

}

- (IBAction)ScreenShot;

@end

AND

ScreenCapture.mm

#import "ScreenCapture.h"

#import "QuartzCore/QuartzCore.h"

@implementation ScreenCaptureDelegate

- (IBAction)ScreenShot {

UIGraphicsBeginImageContext(self.view.bounds.size);

[self.view drawViewHierarchyInRect:self.view.frame afterScreenUpdates:NO];

UIImage *screenshotimage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

UIImageWriteToSavedPhotosAlbum(screenshotimage, nil, nil, nil);

}

@end

static ScreenCaptureDelegate *delegateObject = nil;

// When native code plugin is implemented in .mm / .cpp file, then functions

// should be surrounded with extern "C" block to conform C function naming rules

extern"C" {

void _showPopUp(const char* Picture)

{

[delegateObjectScreenShot];

}

}

When I run this on the ipad I only get blank images.I have updated my ipad to use ios7.

I even tried with the renderInContext command, even there I get blank images. So i tried with the drawViewHierarchyInRect .

I even used the snapshotViewAfterScreenUpdates but here I dont even get a blank image.

Am i going wrong somewhere?