在下面的代码中，我仅在发生特定事件时才尝试调用handleEvent方法。为此，我在事件发生的地方发布了一个通知(下面的代码未显示)，以便观察者和handleEvent可以观察到该通知(如下代码)。
我想要一个警报viewController弹出并输入文本，以便我可以接收它。
但我得到以下错误:
Warning: Attempt to present <UIAlertController: 0x7f9d1347ed90> on <MSMDemoFirstViewController: 0x7f9d1347e920> whose view is not in the window hierarchy!
尽管我正在使用单例，但我无法理解，但无法正确获取alertViewController。任何帮助都会很有用。
#import "MSMDemoFirstViewController.h"
#import "CAMDOReporter.h"
static MSMDemoFirstViewController * instance = nil;
@interface MSMDemoFirstViewController ()
@end
@implementation MSMDemoFirstViewController
+ (MSMDemoFirstViewController *)sharedInstance {
// Singleton implementation
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
if (instance == nil) {
instance = [[MSMDemoFirstViewController alloc] init];
}
});
return instance;
}
+(void)load{
[[NSNotificationCenter defaultCenter] addObserver:[MSMDemoFirstViewController sharedInstance] selector:@selector(handleEvent:) name:EVENT_OCCURRED object:nil];
}
+(void) initialize{
}
- (void) viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
//[[CAMDOReporter sharedInstance] startApplicationTransaction:@"DemoEventApplicationTransaction"];
// [self showAlert];
}
-(void)showAlert{
NSLog(@"2ew");
NSString *title = NSLocalizedString(@"A Short Title Is Best", nil);
NSString *message = NSLocalizedString(@"A message should be a short, complete sentence.", nil);
NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil);
NSString *otherButtonTitle = NSLocalizedString(@"OK", nil);
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:title message:message preferredStyle:UIAlertControllerStyleAlert];
[alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) {
// If you need to customize the text field, you can do so here.
}];
// Create the action.
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
NSLog(@"The simple alert's cancel action occured.");
}];
UIAlertAction *otherAction = [UIAlertAction actionWithTitle:otherButtonTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
NSLog(@"The \"Text Entry\" alert's other action occured.");
}];
// Add the action.
[alertController addAction:cancelAction];
[alertController addAction:otherAction];
[self presentViewController:alertController animated:YES completion:nil];
}
-(void)handleEvent:(NSNotification *)note{
NSLog(@"Handle Crash Event");
NSDictionary *crashData = [note userInfo];
if(crashData !=nil){
//Implement any UI Logic to get any response from the user. e.g. AlertView, TextFields.
//Once the feedback is received convert it into NSString and send the data.
// Show a text entry alert with two custom buttons.
[[MSMDemoFirstViewController sharedInstance] showAlert];
NSString *feedback=[[NSUserDefaults standardUserDefaults] objectForKey:@"crashDetails"];
[[CAMDOReporter sharedInstance] setCustomerFeedback:feedback];
}
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
现在我得到的输出是:
2015-01-21 20:17:45.762 CAMAADemo[18891:1558312] Handle Crash Event
2015-01-21 20:17:45:762 CAMAADemo[18891:1807] Posting Notification about crash
2015-01-21 20:17:45.762 CAMAADemo[18891:1558312] 2ew
2015-01-21 20:17:45.778 CAMAADemo[18891:1558312] Warning: Attempt to present <UIAlertController: 0x7ff5d2273580> on <MSMDemoFirstViewController: 0x7ff5d2204be0> whose view is not in the window hierarchy!
这意味着该调用将要使用showAlert方法，但随后却遇到了同样的错误。
甚至以下代码也无济于事。
-(void)viewDidLoad{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleCrashEvent:) name:CAMAA_CRASH_OCCURRED object:nil];
}
-(void)showAlert{
NSLog(@"2ew");
NSString *title = NSLocalizedString(@"A Short Title Is Best", nil);
NSString *message = NSLocalizedString(@"A message should be a short, complete sentence.", nil);
NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil);
NSString *otherButtonTitle = NSLocalizedString(@"OK", nil);
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:title message:message preferredStyle:UIAlertControllerStyleAlert];
[alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) {
// If you need to customize the text field, you can do so here.
}];
// Create the action.
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
NSLog(@"The simple alert's cancel action occured.");
}];
UIAlertAction *otherAction = [UIAlertAction actionWithTitle:otherButtonTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
NSLog(@"The \"Text Entry\" alert's other action occured.");
}];
// Add the action.
[alertController addAction:cancelAction];
[alertController addAction:otherAction];
[self presentViewController:alertController animated:YES completion:nil];
}
-(void)handleCrashEvent:(NSNotification *)note{
NSLog(@"Handle Crash Event");
NSDictionary *crashData = [note userInfo];
if(crashData !=nil){
//Implement any UI Logic to get any response from the user. e.g. AlertView, TextFields.
//Once the feedback is received convert it into NSString and send the data.
// Show a text entry alert with two custom buttons.
[self showAlert];
NSString *feedback=[[NSUserDefaults standardUserDefaults] objectForKey:@"crashDetails"];
[[CAMDOReporter sharedInstance] setCustomerFeedback:feedback];
}
}
最佳答案
代码的问题是您创建了一个全新的视图控制器，并显示了来自新控制器的警报。但是没有显示该控制器，因此显示错误消息。
修复此代码的正确方法是从实际显示的视图控制器显示警报。
为此，将实际的视图控制器实例注册为通知处理程序，而不是在load方法中注册该类。
进行以下更改:
load方法。 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleEvent:) name:EVENT_OCCURRED object:nil];的调用移至viewDidLoad方法。 handleEvent:更改为实例方法。 [[[self alloc]init] showAlert];更改为[self showAlert];。 dealloc方法并取消注册通知查看器。 关于ios - AlertViewController-其 View 不在窗口层次结构中，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28081097/