向UINavigationBar（iPhone）添加左键 [英] Adding left button to UINavigationBar (iPhone)

问题描述

我创建了一个新的基于导航的iPhone应用程序。我将它添加到RootViewController。

I've created a new navigation based iPhone app. I added this to the RootViewController.

- (void)viewDidLoad {
    [super viewDidLoad];
    UIBarButtonItem *addButton = [[UIBarButtonItem alloc] init];
self.navigationItem.leftBarButtonItem = addButton;
self.navigationItem.leftBarButtonItem.enabled = YES;
}

但是不显示左按钮。有什么我需要做的吗？

No left button displays however. Is there something I need to do?

推荐答案

你没有定义按钮的实际功能。这是我的应用程序中的一行：

You don't define what the button actually does. This is a line from my app:

self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(cancelEdit:)];

cancelEdit：，选择器，在当前类（self）并定义为：

cancel, the selector, is in the current class (self) and is defined as:

- (void) cancelEdit: (id) sender;

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