hide and show left navigation bar button on demand

问题:

I added my left navigation bar button using the storyboard. but I want it to hide when I first load the screen. And then in response to something else, I want it to show. The navigation bar has a method for hiding the back button. But there is no method for hiding/showing the left button. Is there a simple way for doing this? Or do I have to use two methods: the hiding method creates an empty button and the showing method creates the correct button? The button in question is just the Add template that iOS provides (which makes it easy to just use the one in the storyboard than to create my own).

回答1:

Here is how I solved it

-(void) hideAndDisableRightNavigationItem
{
    [self.navigationItem.rightBarButtonItem setTintColor:[UIColor clearColor]];
    [self.navigationItem.rightBarButtonItem setEnabled:NO];
}

-(void) showAndEnableRightNavigationItem
{
    [self.navigationItem.rightBarButtonItem setTintColor:[UIColor blackColor]];
    [self.navigationItem.rightBarButtonItem setEnabled:YES];
}

回答2:

Swift version of @learner answer

func hideAndDisableRightNavigationItem (){
  self.navigationItem.rightBarButtonItem?.enabled = false
  self.navigationItem.rightBarButtonItem?.tintColor = UIColor.clearColor()
}

func showAndEnableRightNavigationItem(){
   self.navigationItem.rightBarButtonItem?.enabled = true
   self.navigationItem.rightBarButtonItem?.tintColor = UIColor. blackColor()
}

回答3:

Here is what I did. On the initial screen I wanted to hide the navigation bar:

 self.navigationController.navigationBarHidden = YES;

On the second screen I wanted to show the navigation bar so I set:

 self.navigationController.navigationBarHidden = NO;