當按下UINavigationController上的后退按鈕時，如何調用方法？ （蘋果手機）

Question

當按下UINavigationController上的后退按鈕時，如何調用方法。 我需要能夠在顯示上一個視圖之前調用一個方法。 這可能嗎？ 如果是這樣，有人可以建議如何做嗎？

Answer 1

一種快速的解決方案是為viewWillDisappear：方法添加一個實現。 一旦viewController響應后退按鈕的按下而消失，它將被觸發。

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

另一種解決方案是將自定義響應器添加到“后退”按鈕。 您可以按如下方式修改viewController的init方法：

- (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;
}

然后可以使用以下選擇器方法。 確保正確關閉viewController，否則導航控制器將不會彈出。

- (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];

創建一個自定義的后退按鈕，並使用該選擇器調用所需的方法。 並且還使用[self.navigationController popViewControllerAnimated：TRUE];

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

Answer 3

我認為我找到了一種“干凈”的方法：

首先，將您的視圖控制器設置為符合UINavigationControllerDelegate協議

@interface MyViewController () <UINavigationControllerDelegate>

然后，將其定義為委托

- (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協議中的此方法：

#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

最簡單的方法是將代碼放入ViewController中，該代碼將在按下后退按鈕時顯示。 您可以使用viewWillAppear

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

請注意，由於任何其他原因在顯示視圖時也會執行此操作，因此，如果只希望在按下后退按鈕時執行此視圖，則必須使用委托： UINavigationControllerDelegate