Hiding Navigation Bar By Set Alpha.

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
      [self.navigationController.navigationBar setAlpha:0.0];
  // [self.navigationController.navigationBar setAlpha:1.0];
   
}
 - (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [self.navigationController.navigationBar setAlpha:1.0];
  
}