iOS7之后，苹果开放出一个通知：UIApplicationUserDidTakeScreenshotNotification，截屏时系统就会发出这个通知，需要你注册这个通知，就能捕捉到截屏图片。

//注册截屏通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(GetScreenShotAction:) name:UIApplicationUserDidTakeScreenshotNotification object:nil];

方法实现：

• (void)GetScreenShotAction:(NSNotification *)notification{
  NSLog(@"捕捉截屏事件");

  //获取截屏图片
  UIImage *image = [UIImage imageWithData:[self imageDataScreenShot]];

  //显示图片
  UIImageView *imgV = [[UIImageView alloc]initWithImage:image];
  imgV.frame = [UIScreen mainScreen].bounds;

  UIView *backView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT)];
  backView.backgroundColor = [[UIColor grayColor] colorWithAlphaComponent:0.8];

  UIButton shareBtn = [UIButton buttonWithType:UIButtonTypeSystem];
  shareBtn.titleLabel.font = [UIFont systemFontOfSize:17.0];
  [shareBtn setTintColor:[UIColor whiteColor]];
  shareBtn.frame = CGRectMake(SCREEN_WIDTH/5,SCREEN_HEIGHT ,SCREEN_WIDTH3/5,50);
  [shareBtn.layer setMasksToBounds:YES];
  [shareBtn.layer setBorderWidth:1];
  shareBtn.layer.cornerRadius = 6;
  [shareBtn setTitle:@"分享给好友" forState:UIControlStateNormal];
  shareBtn.backgroundColor = [SouFunIMUtilityHelper colorWithHexString:@"#B22222"];
  [shareBtn addTarget:self action:@selector(shareBtn:) forControlEvents:UIControlEventTouchUpInside];

  [backView addSubview:imgV];
  [backView addSubview:shareBtn];

  UIWindow *window = [UIApplication sharedApplication].keyWindow;
  [window addSubview:backView];

  [UIView animateWithDuration:1.0 animations:^{
  imgV.transform = CGAffineTransformMakeScale(0.8, 0.8);
  shareBtn.transform = CGAffineTransformMakeTranslation(0, -50);
  }];
  //3秒后消失
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
  [backView removeFromSuperview];
  });
  }

获取截屏图片data：

• (NSData *)imageDataScreenShot
  {
  CGSize imageSize = CGSizeZero;
  imageSize = [UIScreen mainScreen].bounds.size;

  UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
  CGContextRef context = UIGraphicsGetCurrentContext();
  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 ([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)])
  {
  [window drawViewHierarchyInRect:window.bounds afterScreenUpdates:YES];
  }
  else
  {
  [window.layer renderInContext:context];
  }
  CGContextRestoreGState(context);
  }

  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  return UIImagePNGRepresentation(image);
  }