[[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(userDidTakeScreenshot:)
                                                 name:UIApplicationUserDidTakeScreenshotNotification
                                               object:nil];

- (void)userDidTakeScreenshot:(NSNotification *)notification {
    // 手动截取当前屏幕图片
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    UIImageView* imageView = [[UIImageView alloc] initWithImage:[self takeScreenshot]];
    imageView.frame = CGRectMake(10, 10, SCREEN_WIDTH - 20, SCREEN_HEIGHT - 20);
    [window addSubview:imageView];
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [imageView removeFromSuperview];
    });
    
    
}

-(UIImage *)takeScreenshot {
    CGSize imageSize = CGSizeZero;
    CGSize screenSize = [UIScreen mainScreen].bounds.size;
    UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
    
    if (UIInterfaceOrientationIsPortrait(orientation)) {
        imageSize = screenSize;
    } else {
        imageSize = CGSizeMake(screenSize.height, screenSize.width);
    }
    
    UIGraphicsBeginImageContextWithOptions(imageSize, false, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    if (context) {
        for (UIWindow *window in [UIApplication sharedApplication].windows) {
            CGContextSaveGState(context);
            CGContextTranslateCTM(context, window.center.x, window.center.y);
            CGContextConcatCTM(context, window.transform);
            CGContextTranslateCTM(context, -window.bounds.size.width * window.layer.anchorPoint.x, -window.bounds.size.height * window.layer.anchorPoint.y);
            
            if (orientation == UIInterfaceOrientationLandscapeLeft) {
                CGContextRotateCTM(context, M_PI_4);
                CGContextTranslateCTM(context, 0, -imageSize.width);
            } else if (orientation == UIInterfaceOrientationLandscapeRight) {
                CGContextRotateCTM(context, - M_PI_2);
                CGContextTranslateCTM(context, -imageSize.height, 0);
            } else if (orientation == UIInterfaceOrientationPortraitUpsideDown) {
                CGContextRotateCTM(context, M_PI);
                CGContextTranslateCTM(context, -imageSize.width, -imageSize.height);
            }
            
            if ([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)]) {
                [window drawViewHierarchyInRect:window.bounds afterScreenUpdates:YES];
            } else {
                [window.layer renderInContext:context];
            }
            
            CGContextRestoreGState(context);
        }
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return image;
}

但是这个截屏没有状态栏，想要状态栏使用这个代码：
https://github.com/Realank/OTScreenshotHelper