如何解决如果我将我的应用程序移至后台,然后在iOS中移至前台,则呈现的视图控制器将被关闭
我有一个要求,当用户将应用程序移至背景 applicationDidEnterBackground 时,必须用黑色布局覆盖屏幕,以保护屏幕上某些敏感数据的私密性。因此,为此,我利用AppDelegate函数在背景中呈现黑色,然后通过在前景 applicationDidEnterBackground 时将其消除而将其删除。代码是:
#import "AppDelegate.h"
@interface AppDelegate ()
@end
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.
return YES;
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
UIViewController *blankViewController = [UIViewController new];
blankViewController.view.backgroundColor = [UIColor blackColor];
[self.window makeKeyAndVisible];
[self.window.rootViewController presentViewController:blankViewController animated:NO completion:NULL];
}
- (void)applicationWillEnterForeground:(UIApplication *)application {
[self.window.rootViewController dismissViewControllerAnimated:false completion:nil];
}
@end
现在,在我的应用程序中一切正常,但是在一个屏幕上,我通过单击以下按钮来显示 ViewContollerB :[self presentViewController:webview animated:YES completion:nil];
该应用程序通常在移动时会被黑色覆盖到后台,但是当我在此之后将应用程序带到前台时,显示的 ViewContollerB 也被关闭了。如何防止我提出的ViewController一旦退出背景就被解雇了?
解决方法
您正在尝试执行以下操作:rootviewcontroller A呈现一个空白的viewcontrollerB。您的应用程序进入后台,并且从此处显示ViewcontrollerC。现在B关闭,因为A同时显示B和C,这是不允许的。
您将需要检查rootviewcontroller是否呈现任何视图控制器,以及是否递归呈现其他视图控制器。您可以使用视图控制器上的属性presentedViewController
来检查这些内容。
就个人而言,我会(在所有视图控制器都继承的基类的视图控制器中)保留一个变量,以检查该变量是否可见(通过跟踪viewDidAppear
和viewDidDisappear
)。如果这是可见的,则在顶部添加一个空白视图。
在Swift中回答,因为没有编辑器就无法信任Objective-C:
class BaseViewController: UIViewController {
var appeared = false
func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated: animated)
appeared = true
}
func viewDidDisappear(animated: Bool) {
super.viewDidDisappear(animated: animated)
appeared = false
}
}
然后,您需要从AppDelegate
中触发该视图控制器中捕获的通知,然后在顶部显示空白视图。
创建一个名为applicationDidEnterBackground
的新'UIViewController'并将其加载到
- (void)applicationDidEnterBackground:(UIApplication *)application {
OverLayViewController *blankViewController = [OverLayViewController new];
blankViewController.view.backgroundColor = [UIColor blackColor];
[self.window makeKeyAndVisible];
UIViewController *rvc = self.window.rootViewController;
UIViewController *pvc = rvc.presentedViewController; // you may need to loop through presentedViewControllers if you have more than one
if(pvc != nil) {
[pvc presentViewController: blankViewController animated: NO completion:nil];
}
else{
[self.window.rootViewController presentViewController: blankViewController animated: NO completion:nil];
}
}
- (void)applicationWillEnterForeground:(UIApplication *)application {
UIViewController *test = [self topViewController];
if ([test isKindOfClass:[OverLayViewController class]]) {
[test dismissViewControllerAnimated:false completion:nil];
}
}
- (UIViewController*)topViewController {
return [self topViewControllerWithRootViewController:[UIApplication sharedApplication].keyWindow.rootViewController];
}
-(UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController {
if ([rootViewController isKindOfClass:[UITabBarController class]]) {
UITabBarController* tabBarController = (UITabBarController*)rootViewController;
return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
} else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
UINavigationController* navigationController = (UINavigationController*)rootViewController;
return [self topViewControllerWithRootViewController:navigationController.visibleViewController];
} else if (rootViewController.presentedViewController) {
UIViewController* presentedViewController = rootViewController.presentedViewController;
return [self topViewControllerWithRootViewController:presentedViewController];
} else {
return rootViewController;
}
}
方法
dismissViewContoller
在这种情况下,@deprecated
代码将不适用于您的网络视图。
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