在没有UINavigationController的情况下将backBarButtonItem添加到navigationItem？

Question

我有一个UIViewController，我在InterfaceBuilder中添加一个navigationItem来查看标题，我发现我无法将backBarButtonItem拖到navigationItem，只能添加leftBarButtonItem和rightBarButtonItem。所以我尝试在我的控制器代码中将backBarButtonItem添加到navigationItem元素：

- (void)viewWillAppear:(BOOL)animated {
   UIBarButtonItem *_backButton = [[UIBarButtonItem alloc] initWithTitle:@"Back"   style:UIBarButtonItemStyleDone target:nil action:nil];
   self.myNavigationItem.backBarButtonItem = _backButton;
  [_backButton release];
}

但是视图上仍然没有backBarButtonItem？如何解决？

Answer 1

你必须实际设置leftBarButtonItem，而不是backBarButtonItem，然后才设置self.hidesBackBarButtonItem，如下所示：

- (void)viewWillAppear:(BOOL)animated {
 UIBarButtonItem *_backButton = [[UIBarButtonItem alloc] initWithTitle:@"Back"   style:UIBarButtonItemStyleDone target:nil action:nil];
    self.navigationItem.hidesBackButtonItem = YES;
     self.myNavigationItem.leftBarButtonItem = _backButton;
    [_backButton release];
}