NavigationBar back button disappears
<p>I used codes below to display the uiimage on navigation bar </p>

<pre><code>-(void)hideTopBanner:(bool)b;
{
    if(b)
    {

        [UIView animateWithDuration:0.35 animations:^{

         UIView *bannerView =[self.navigationController.navigationBar viewWithTag:999];
            [bannerView setFrame:CGRectMake(-320, 8, 144, 30)];


        }];
    }
    else {

        [UIView animateWithDuration:0.35 animations:^{



            UIView *bannerView =[self.navigationController.navigationBar viewWithTag:999];
            [bannerView setFrame:CGRectMake(88 , 8, 144, 30)];



        }];
    }
}
</code></pre>

<p>//--------------</p>

<pre><code>UIImageView *bgImageView =  [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"topbg1.png"]] ;
[bgImageView setFrame:CGRectMake(0, 0, 320, 46)];
[self.navigationController.navigationBar addSubview:bgImageView];
bgImageView.tag=999;
[bgImageView release];
</code></pre>

<p>I try to use</p>

<pre><code>  UIBarButtonItem *myBarButtonItem = [[UIBarButtonItem alloc] init];
   myBarButtonItem.title = @back"; // or whatever text you want
    self.navigationItem.backBarButtonItem = myBarButtonItem;
    [myBarButtonItem release];
</code></pre>

<p>display a back button ,but nothing displayed</p>

<p>but when it navigates to another view controller.
The back button on navigation bar disappear.</p>

<p>Welcome any comment</p>
