如何在应用程序委托 (obj-c) 中添加 UIAlertController [英] How do I add a UIAlertController in app delegate (obj-c)
问题描述
这是我在 UIAlertView 被弃用之前使用的代码:
This is the code I was using prior to UIAlertView being deprecated:
//OLD UIALERTVIEW
- (void)applicationDidBecomeActive:(UIApplication *)application {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
// check to see if newer version exists to alert the user
BOOL updateAvailable = NO;
NSDictionary *updateDictionary = [NSDictionary dictionaryWithContentsOfURL:[NSURL URLWithString:@"PLIST_URL_HERE"]];
NSArray *items = [updateDictionary objectForKey:@"items"];
NSDictionary *itemDict = [items lastObject];
NSDictionary *metaData = [itemDict objectForKey:@"metadata"];
NSString *newversion = [metaData valueForKey:@"bundle-version"];
NSString *currentversion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"];
//updateAvailable = [newversion compare:currentversion options:NSNumericSearch] == NSOrderedDescending; //default code
updateAvailable = [@"1.3" compare:currentversion options:NSNumericSearch] == NSOrderedDescending; //force update
//updateAvailable = [@"1.1" compare:currentversion options:NSNumericSearch] == NSOrderedDescending; //force no update
if (updateAvailable) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"UPDATE AVAILABLE" message:@"Click OK to update the application to the latest version" delegate:self cancelButtonTitle:@"Later" otherButtonTitles:@"OK", nil];
[alert show];
}
}
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex != [alertView cancelButtonIndex]) {
// point to the pList on dropbox to install the
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"PLIST_URL_HERE"]];
exit(0);
我正在尝试更新它以改用 UIAlertController.这是我为此使用的代码
I am trying to update it to use UIAlertController instead. heres the code I'm using for that
//NEW UIACTIONCONTROLLER
- (void)applicationDidBecomeActive:(UIApplication *)application {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
// check to see if newer version exists to alert the user
BOOL updateAvailable = NO;
NSDictionary *updateDictionary = [NSDictionary dictionaryWithContentsOfURL:[NSURL URLWithString:@"PLIST_URL_HERE"]];
NSArray *items = [updateDictionary objectForKey:@"items"];
NSDictionary *itemDict = [items lastObject];
NSDictionary *metaData = [itemDict objectForKey:@"metadata"];
NSString *newversion = [metaData valueForKey:@"bundle-version"];
NSString *currentversion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"];
//updateAvailable = [newversion compare:currentversion options:NSNumericSearch] == NSOrderedDescending; //default code
updateAvailable = [@"1.3" compare:currentversion options:NSNumericSearch] == NSOrderedDescending; //force update
//updateAvailable = [@"1.1" compare:currentversion options:NSNumericSearch] == NSOrderedDescending; //force no update
if (updateAvailable) {
UIAlertController * alert= [UIAlertController alertControllerWithTitle:@"UPDATE AVAILABLE" message:@"Click OK to update the application to the latest version" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"PLIST_URL_HERE"]];
exit(0);
}];
UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil];
[alert addAction:ok];
[alert addAction:cancel];
[self presentViewController:alert animated:YES completion:nil];
}
}
问题是这段代码:
[self presentViewController:alert animation:YES completion:nil];
[self presentViewController:alert animated:YES completion:nil];
给我这个错误:
/Users/liz/Desktop/CactusQueuesGit/CactusQueue/AppDelegate.m:154:15:AppDelegate"没有可见的@interface 声明了选择器presentViewController:animated:completion:"
/Users/liz/Desktop/CactusQueuesGit/CactusQueue/AppDelegate.m:154:15: No visible @interface for 'AppDelegate' declares the selector 'presentViewController:animated:completion:'
我可以将该代码放在 viewDidLoad 中，但我不希望每次用户转到 TableView 时都弹出警报.我只希望它仅在应用程序打开时加载.
I can put that code in viewDidLoad but I don't want the alert popping up every time the users go to the TableView. I just want it to load ONLY when the app is opened.
我该怎么做?
推荐答案
Per Apple 文档，UIAlertController 就像任何其他需要视图控制器作为基础来呈现的视图控制器一样.
Per Apple Documentation, UIAlertController is just like any another view controller which needs a view controller as base to present on.
要从 AppDelegate 呈现一个 UIAlertController，您可以创建一个临时窗口，其中包含一个空的视图控制器并在其顶部呈现.像这样:
To present an UIAlertController from AppDelegate, you can create a temporary window with an empty view controller in it and present on top of it. Something like this:
self.alertWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.alertWindow.rootViewController = [[UIViewController alloc] init];
self.alertWindow.windowLevel = UIWindowLevelAlert + 1;
[self.alertWindow makeKeyAndVisible];
[self.alertWindow.rootViewController presentViewController:alertControl animated:YES completion:nil];
警报解除后，此窗口将自动从内存中取出.
如果 rootViewController 已初始化并添加到视图层次结构中，您还可以在它上显示警报.
You can also present your alert on rootViewController if it has been initialized and is added in view hierarchy.
我希望你明白为什么你现在会收到这个错误.从技术上讲，AppDelegate 不是视图控制器，因此不会响应 presentViewController:animated:completion: 方法.
I hope you got why you are getting this error now. Technically, AppDelegate is not a view controller and so does not respond to presentViewController:animated:completion: method.
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