三个导航栏Item的区别（leftBarButtonItem/backBarButtonItem/backItem）三个导航栏Item的区别（leftBa

三种导航栏Item为：
1、self.navigationItem.leftBarButtonItem
2、self.navigationItem.backBarButtonItem
3、self.navigationController.navigationBar.backItem
其中UINavigationItem有三种：backBarButtonItem、leftBarButtonItem、rightBarButtonItem。
一、leftBarButtonItem
如果设置了leftBarButtonItem，会替换掉backBarButtonItem。但可以设置leftItemsSupplementBackButton为YES，来同时显示leftBarButtonItem和backBarButtonItem。
leftBarButtonItem的自定义方式如下：

UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom]; [backBtn setTitleColor:[UIColor colorWithRed:74 / 255.0 green:74 / 255.0 blue:74 / 255.0 alpha:1.0] forState:UIControlStateNormal]; [backBtn setTitle:@"返回" forState:UIControlStateNormal]; [backBtn setImage:[UIImage imageNamed:@"NewBackButton"] forState:UIControlStateNormal]; [backBtn addTarget:self action:@selector(popViewController:) forControlEvents:UIControlEventTouchUpInside]; [backBtn sizeToFit]; self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backBtn]; - (void)popViewController:(UIButton *)sender { [self.navigationController popViewControllerAnimated:YES]; }

二、backBarButtonItem
backBarButtonItem是返回按钮，可以自定义。注意：假如想实现第二个ViewController的backBarButtonItem，就要先在第一个ViewController中设置backBarButtonItem。
返回按钮backBarButtonItem的自定义方式如下：

UIBarButtonItem *backBarButtonItem = [[UIBarButtonItem alloc] init]; [backBarButtonItem setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor colorWithRed:74 / 255.0 green:74 / 255.0 blue:74 / 255.0 alpha:1.0], NSFontAttributeName:[UIFont systemFontOfSize:18]} forState:UIControlStateNormal]; backBarButtonItem.title = [NSString stringWithFormat:@"返回"]; backBarButtonItem.image = [UIImage imageNamed:@"NewBackButton"]; self.navigationItem.backBarButtonItem = backBarButtonItem;

这样才会在第二个ViewController中有效果出现，显示返回按钮样式；?否则，无设置效果。
【三个导航栏Item的区别（leftBarButtonItem/backBarButtonItem/backItem）】三、backItem
backItem只是一个只读属性，不能设置。