iOS 7 Changing UINavigationBar titleView alpha

问题:

So I am using the UINavigationBar component of iOS7, but not the UINavigationController itself. When I push a new view with my custom navigation controller, I want to change the title's alpha to 0.0 and then back, but I can't seem to get it work.

I am trying to do this

vc1.navBar.topItem.titleView.alpha = 0.1;

It doesn't seem to have any effect. Am I missing something here, is there a correct way to achieve this?

回答1:

This is how I would do it:

• In viewWillAppear: of the pushed viewController, I would set it the alpha to 0 using:

  [self.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                                                              [[UIColor whiteColor] colorWithAlphaComponent:0],
                                                              NSForegroundColorAttributeName,
                                                              [UIFont fontWithName:@"Helvetica-Bold" size:16.0],
                                                              NSFontAttributeName,
                                                               nil]];
  

• In viewDidAppear:, set it's alpha back to 1. Here you don't really need to set it's alpha to 1, just setting it to plain [UIColor whiteColor] will do the trick.

One other thing you could do is, toggle HIDDEN property in the 2 methods.

Setting the alpha of the titleView did not work in my case so I used the above code. It hides the title. In case you want a similar effect with the back button, you set the alpha of the backButton using self.navigationItem.backBarButtonItem.customView.alpha =

回答2:

You can set the titleView hidden in viewWillAppear

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    self.navigationItem.titleView.hidden = YES;
}

You can't set the titleView alpha until viewDidAppear

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    self.navigationItem.titleView.alpha = 0.5f;
}

回答3:

You can try this one -

[self.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                                                                    [UIColor colorWithRed:125/255.0 green:178/255.0 blue:15/255.0 alpha:0.2],
                                                                    NSForegroundColorAttributeName,
                                                                    [UIFont fontWithName:@"Helvetica-Bold" size:16.0],
                                                                    NSFontAttributeName,
                                                                     nil]];

If you just want to change the title attributes. Or this one to change bar alpha :

[self.navigationBar setBarTintColor:[UIColor colorWithRed:125/255.0 green:178/255.0 blue:15/255.0 alpha:0.2]];