iphone - 检测何时推送 Viewcontroller

Question

我正在尝试检测何时推送 ViewController。所以我跟着苹果的文档http://developer.apple.com/library/ios/#documentation/uikit/reference/UINavigationBarDelegate_Protocol/Reference/Reference.html ，关于 NavegationBar 委托(delegate)，但我没有想出如何让它成功工作。我在我的 ViewController 中放置了以下代码，但它没有检测到它正在推送。我做错了什么？

- (void)navigationBar:(UINavigationBar *)navigationBar didPushItem:(UINavigationItem *)item, {
    NSLog(@"didPushItem: %@", item);
    [self showimage];
}

Answer 1

不清楚您需要做什么，但有几种 UIViewController 方法可以辨别其上下文。下面有两个，docs 中还有两个。

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    BOOL pushed = [self isMovingToParentViewController];

    printf("viewWillAppear     %d\n", pushed);

}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    BOOL popped = [self isMovingFromParentViewController];

    printf("viewWillDisappear     %d\n", popped);

}