ios - navigationController alpha 会重置吗？当应用程序从后台激活时

Question

1. 我在 AUIController 中，navigationController.navigationBar.alpha == 0.500
2. 我按下了主页按钮。
3. 我单击了 appIcon 以返回 AUIController。 navigationController.navigationBar.alpha 到 1.000

我该怎么做才能保持 navigationController.navigationBar 的 alpha = 0.5000 ；

我试过了..

AUIController : UIViewController  <...,UINavigationControllerDelegate>

- (void) navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {

    if (viewController == self) {
            //NSLog(@"self");
        //self.navigationController.navigationBar.tintColor = [UIColor colorWithRed:0.000 green:0.000 blue:0.000 alpha:1.000];
            self.navigationController.navigationBar.alpha = 0.500;
            self.navigationController.navigationBar.translucent = YES;
        } else {
            self.navigationController.navigationBar.alpha = 1.000;
            self.navigationController.navigationBar.translucent = NO;
        }
    }

但是当应用程序激活时，alpha 0.50 变为 1.00willShowViewController 不会被调用

Answer 1

您可以使用 KVO 来做到这一点。在 viewDidLoad的 AUIController添加此代码 [self.navigationController.navigationBar addObserver:self forKeyPath:@"alpha" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:(__bridge void *)(self)];

并实现这个功能:

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    NSLog([change description]);
    UIViewController *viewController = (__bridge UIViewController*)context;
    if ([viewController isKindOfClass:[AUIViewController class]]) {
        if (self.navigationController.navigationBar.alpha == 1) {
            self.navigationController.navigationBar.alpha = 0.500;
            self.navigationController.navigationBar.translucent = YES;
        }
    }
}