如何禁用“完成”当键盘滑入时，导航栏中的按钮？

Question

我相信我无法禁用它，因为我无法以编程方式访问该 UIBarButttonItem
（使用 viewWithTag 或 rightBarButtonItem ）。

有什么建议（除了添加没有 IB 的接口之外）？
作为测试，我还尝试以编程方式添加按钮（在导航栏的左侧），但它没有显示在导航栏中。

相关代码（在MyEditorViewControler.m中）：

    - (void)textFieldDidBeginEditing:(UITextField *)sender { //successfully executes when keyboard slides in

        UINavigationItem *item = self.navigationItem; //item  = 0x6420e0  OK.  (value at debugger breakpoints)
        UIBarButtonItem *doneButton4    = (UIBarButtonItem *) [self.view viewWithTag:44]; //doneButton4 = 0x0,  not OK.
        doneButton4.enabled = NO; 
    }
    - (void)textFieldDidEndEditing:(UITextField *)sender {  //successfully executes when keyboard  slides out.  
        ...
        UIButton* doneButton = (UIButton *)[self.view viewWithTag:44]; //Attempt to re-enable button.
        doneButton.enabled = YES;
    }
    - (void)viewDidLoad {   //Attempt to programmatically add a *left* button to the nav bar. Result: Button does not display in nav bar.
        .... 
        UIBarButtonItem *leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(done)];
        self.navigationItem.leftBarButtonItem = leftBarButtonItem;
        [leftBarButtonItem release];
    }

详细信息
我认为这是一种常见情况，因为“完成”按钮：
a) 是从 IB 库添加到导航栏的 UIBarButttonItem，该导航栏位于具有一些 UITextField 的滚动视图中。
b）按预期运行（保存用户输入的数据等），
除了键盘出现时不会被禁用。
c) IB>检查员>栏按钮项目属性显示：
标识符 = 完成
标签 = 44
类 = UIBarButtonItem

Answer 1

你应该只是使用

UIBarButtonItem *doneButton = self.navigationItem.leftBarButtonItem; 
doneButton.enabled = YES;

//Both of these should work, you shouldn't need any type of IBOutlets for this

UINavigationItem *item = self.navigationItem;
UIBarButtonItem *doneButton = item.leftBarButtonItem;

Answer 2

您可以收听键盘滑入时发布的通知 (UIKeyboardWillShowNotification)：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];

然后实现 -keyboardWillShow:。

-(void)keyboardWillShow {
    UIButton *button = self.navigationItem.leftBarButtonItem;
    button.enabled = NO;
}

要再次重新启用该按钮，请对 UIKeyboardDidHideNotification 执行相同的操作