如何添加按鈕到UINavigationController

Question

我有下面的代碼，添加一個導航控制器到模態視圖。導航欄和視圖全部顯示正常，但右側按鈕不顯示。我究竟做錯了什麼？

UpgradesViewController* upgradesViewController = [[UpgradesViewController alloc] initWithNibName:@"UpgradesView" bundle:nil]; 
    upgradesViewController.title = @"Upgrades"; 

    UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:upgradesViewController]; 
    navController.modalTransitionStyle = UIModalTransitionStyleCoverVertical; 
    navController.navigationBar.barStyle = UIBarStyleBlack; 
    UIBarButtonItem* doneButton = [[UIBarButtonItem alloc] initWithTitle:@"Show" style:UIBarButtonItemStylePlain target: self action:nil]; 
    navController.navigationItem.rightBarButtonItem = doneButton; 
    [self presentModalViewController:navController animated:YES]; 

    [navController release]; 
    [upgradesViewController release]; 

Answer 1

將doneButton添加到upgradedesViewController的navigationItem，而不是navController。導航控制器顯示頂部控制器的導航項目，而不是它本身。