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

Question

如何UINavigationController按下a上的后退按钮时如何调用方法.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

一个快速的解决方案是为viewWillDisappear:方法添加一个实现.一旦viewController响应后退按钮消失,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上添加自定义响应器.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.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

我想我发现了一种"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;
    }
}