在iOS中按下后退按钮时如何创建确认弹出窗口？

Question

我想在有人按下我的 iOS 应用程序的“返回”按钮时添加一个弹出窗口，询问用户是否真的想回来。然后，根据用户的响应，我想撤消操作或继续。我尝试在视图的 viewWillDisappear 函数中添加代码，然后编写正确的委托，但它不起作用，因为它总是更改视图然后显示弹出窗口。我的代码是：

    -(void) viewWillDisappear:(BOOL)animated {
       _animated = animated;
       if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
           UIAlertView *alert_undo = [[UIAlertView alloc] initWithTitle:@"UIAlertView"
                                                                message:@"You could be    loosing information with this action. Do you want to proceed?"
                                                               delegate:self
                                                      cancelButtonTitle:@"Go back"
                                                      otherButtonTitles:@"Yes", nil];
           [alert_undo show];
       }
       else [super viewWillDisappear:animated];
   }

委托实现是：

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    NSString *title = [alertView buttonTitleAtIndex:buttonIndex];
    if([title isEqualToString:@"Yes"])
    {
        [super viewWillDisappear:_animated];
    }
}

这根本不起作用。现在有没有人有更好的方法来做到这一点或可能出了什么问题？

非常感谢，

Answer 1

一旦调用 -viewWillDisappear:，就无法阻止您的 viewController 消失。

理想情况下，您应该覆盖navigationBar 的后退按钮，并在其方法中显示警报（其余部分几乎相同）

- (void)viewDidLoad
{
    //...
    UIBarButtonItem *bbtnBack = [[UIBarButtonItem alloc] initWithTitle:@"Back"
                                                                 style:UIBarButtonItemStyleBordered
                                                                target:self
                                                                action:@selector(goBack:)];

    [self.navigationItem setBackBarButtonItem: bbtnBack];
}

- (void)goBack:(UIBarButtonItem *)sender
{
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert"
                                                    message:@"...Do you want to proceed?"
                                                   delegate:self
                                          cancelButtonTitle:@"No"
                                          otherButtonTitles:@"Yes", nil];
    [alert show];
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    switch(buttonIndex) {
        case 0: //"No" pressed
            //do something?
            break;
        case 1: //"Yes" pressed
            //here you pop the viewController
            [self.navigationController popViewControllerAnimated:YES];
            break;
    }
}

注意：不要忘记在这个viewController的.h文件中声明<UIAlertViewDelegate> em>

Answer 2

感谢您的回答，@staticVoidMan！我终于用你的代码做了一些修改。后退按钮无法修改，因此应创建一个附加按钮并隐藏标准按钮。唯一的问题是新的“返回”按钮的样式，它不等于标准的。最终代码为：

- (void)viewDidLoad
{

    self.navigationItem.hidesBackButton = YES;
    UIBarButtonItem *bbtnBack = [[UIBarButtonItem alloc] initWithTitle:@"Back"
                                                                 style:UIBarButtonItemStyleBordered
                                                                target:self
                                                                action:@selector(goBack:)];

    self.navigationItem.leftBarButtonItem = bbtnBack;

}

- (void)goBack:(UIBarButtonItem *)sender
{
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Alert"
                                                    message:@"...Do you want to proceed?"
                                                   delegate:self
                                          cancelButtonTitle:@"No"
                                          otherButtonTitles:@"Yes", nil];
    [alert show];
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    switch(buttonIndex) {
        case 0: //"No" pressed
            //do something?
            break;
        case 1: //"Yes" pressed
            //here you pop the viewController
            [self.navigationController popViewControllerAnimated:YES];
            break;
    }
}