UINavigationController设置返回按钮

UINavigationController 当A界面push到B界面，B界面push到C界面时。

如果要在C界面设置返回B界面的返回按钮，常用的方法是在B界面配置C界面显示的返回按钮。

    UIBarButtonItem *backItem = [[UIBarButtonItem alloc]initWithTitle:@"返回" style:UIBarButtonItemStyleDone target:self action:nil];

    self.navigationItem.backBarButtonItem = backItem;

同理B界面的返回按钮也需要在A界面配置。

上面这种方式是最常用来设置返回键的方式。

官方文档

The bar button item on the left side of the navigation bar allows for navigation back to the previous view controller on the navigation stack. The navigation controller updates the left side of the navigation bar as follows:

• If the new top-level view controller has a custom left bar button item, that item is displayed. To specify a custom left bar button item, set the leftBarButtonItem property of the view controller’s navigation item.
• If the top-level view controller does not have a custom left bar button item, but the navigation item of the previous view controller has a valid item in itsbackBarButtonItem property, the navigation bar displays that item.
• If a custom bar button item is not specified by either of the view controllers, a default back button is used and its title is set to the value of the title property of the previous view controller—that is, the view controller one level down on the stack. (If there is only one view controller on the navigation stack, no back button is displayed.)

1、如果B视图有一个自定义的左侧按钮（leftBarButtonItem），则会显示这个自定义按钮；

2、如果B没有自定义按钮，但是A视图的backBarButtonItem属性有自定义项，则显示这个自定义项；

3、如果前2条都没有，则默认显示一个后退按钮，后退按钮的标题是A视图的标题。