iphone navigationController：在退出当前视图之前等待uialertview响应 [英] iphone navigationController : wait for uialertview response before to quit the current view

问题描述

我有一个带有导航控制器管理的后退按钮的视图，我想检查用户单击后退按钮时是否已保存文件。
如果文件已保存，则返回上一个视图，否则uialertview会询问您是否要保存文件。

I have a view with a back button managed with a navigation controller and I want to check if a file has been saved when the user click on the back button. If the file has been saved you go back in the previous view, else a uialertview ask you if you want to save the file or not.

所以我做了那个，但视图消失了，警报视图出现在后面。

So I did that but the view disapear and the alertview appear after.

-(void)viewWillDisappear:(BOOL)animated {
if(!self.fileSaved){
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"" message:@"Save the file?"  delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes",nil];
    [alert show];
    [alert release];
}
}

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
switch (buttonIndex) {
    case 0:
        NSLog(@"NO");
        break;
    case 1:
        NSLog(@"yes");
        break;
    default:
        break;
}
}

推荐答案

调用viewWillDisappear，已经太晚了。您应该在之前拦截后退按钮。我从来没有这样做过，但我的建议是在viewDidAppear方法中的navigationBar属性上设置委托：

When viewWillDisappear is called, it's already too late. You should intercept the back button earlier on. I have never done it, but my suggestion is to set the delegate on the navigationBar property in your viewDidAppear method:

// save the previous delegate (create an ivar for that)
prevNavigationBarDelegate = self.navigationController.navigationBar.delegate;

self.navigationController.navigationBar.delegate = self;

不要忘记在viewWillDisappear中将其设置回来：

Don't forget to set it back in viewWillDisappear:

self.navigationController.navigationBar.delegate = prevNavigationBarDelegate;

然后截取shouldPopItem方法：

Then intercept the shouldPopItem method:

- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {
     if(!self.fileSaved) {
         UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"" message:@"Save the file?"  delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes",nil];
         [alert show];
         [alert release];

         return NO;
     }

   if ([prevNavigationBarDelegate respondsToSelector:@selector(navigationBar:shouldPopItem:)]) 
      return [prevNavigationBarDelegate navigationBar:navigationBar shouldPopItem:item];

   return YES; 
}

在对话框的YES处理程序中，手动弹出控制器：

And in the YES handler for the dialog, manually pop the controller:

[self.navigationController popViewController:YES];

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