如何在按下UINavigationController上的后退按钮时调用方法？ （苹果手机）

Question

如果按下UINavigationController上的后退按钮，我该如何调用方法？我需要能够在显示上一个视图之前调用方法。这可能吗？如果是这样，请有人建议如何做到这一点？

Answer 1

快速解决方案是为 viewWillDisappear：方法添加实现。只要 viewController 在消除后退按钮时消失，它就会被触发。

- (void)viewWillDisappear:(BOOL)animated {
  //... 
  //make you stuff here
  //... 
}

另一种解决方案是在后退按钮中添加自定义响应器。您可以修改viewController的init方法，如下所示：

- (id)init {
    if (self = [super init]) {
        //other your stuff goes here
        //... 
        //here we customize the target and action for the backBarButtonItem
        //every navigationController has one of this item automatically configured to pop back
        self.navigationItem.backBarButtonItem.target = self;
        self.navigationItem.backBarButtonItem.action = @selector(backButtonDidPressed:);
    }
    return self;
}

然后您可以使用选择器方法，如下所示。请务必正确关闭viewController，否则导航控制器将无法按需弹出。

- (void)backButtonDidPressed:(id)aResponder {
    //do your stuff
    //but don't forget to dismiss the viewcontroller
    [self.navigationController popViewControllerAnimated:TRUE];
}

Answer 2

UIButton *backButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 52, 31)];
[backButton setBackgroundImage:[UIImage imageNamed:@"BackButton.png"] forState:UIControlStateNormal];
//[backButton setTitle:@"CLOSE" forState:UIControlStateNormal];
[backButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
[backButton.titleLabel setFont:[UIFont boldSystemFontOfSize:14.0f]];
[backButton addTarget:self action:@selector(tappedBackButton:) forControlEvents:UIControlStateHighlighted];

UIBarButtonItem* item = [[UIBarButtonItem alloc] initWithCustomView:backButton];

self.navigationItem.leftBarButtonItem = item;
[item release];

创建自定义后退按钮并使用该选择器调用所需的方法。并且还使用[self.navigationController popViewControllerAnimated：TRUE];

- (void)tappedBackButton:(id)button
{
    // call your method here
    [self.navigationController popViewControllerAnimated:TRUE];
} 

Answer 3

我认为我找到了一种“干净”的方法：

首先，将视图控制器设置为符合UINavigationControllerDelegate协议

@interface MyViewController () <UINavigationControllerDelegate>

然后，将其定义为委托

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    // Set this View Controller as the navigation controller delegate
    self.navigationController.delegate = self;

}

最后，使用UINavigationControllerDelegate协议中的此方法：

#pragma mark - Navigation controller delegate
- (void)willMoveToParentViewController:(UIViewController *)parent
{
    // If there is no parent, then it means that the view controller has been removed from the stack, which happens when the back button has been pressed
    if (!parent) {
        NSLog(@"Back button pressed");

        // it can be useful to store this into a BOOL property
        self.backButtonPressed = YES;
    }
}

Answer 4

最简单的方法是将代码放在按下后退按钮时显示的ViewController中。您可以使用viewWillAppear

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
     //Your code here
}

请注意，当出于任何其他原因显示视图时，也会执行此操作，因此，如果您希望仅在按下后退按钮时才会执行此操作，则必须使用委托： UINavigationControllerDelegate