Keyboard dismisses after multiple UIAlertViews are opened

问题

I am having a weird issue with my keyboard automatically closing and then reopening when I open multiple UIAlertViews. If I have a keyboard (from a separate UITextField) and I display a UIAlertView, then upon dismissal of that alert I open another (opening the second one in the didDismissWithButtonIndex). When I dismiss the 2nd one it dismisses the keyboard which then comes back up. If i try this with more than 2 alerts in a row, it will still close my keyboard after the 2nd alert is dismissed, but it doesn't show up until the last alert is dismissed. The problem is that the keyboard delegate functions are NOT called so I cannot respond to it being dismissed. I have other UI elements (textfield and images) that get shifted when the keyboard opens, so when it closes those elements float in the screen and look strange. Any idea why that keyboard automatically dismisses? Thanks

BTW, I use an NSMutableArray of NSDictionary objects to queue up alerts that need to be displayed if an alert is already displayed. I am not creating and displaying more than 1 alert at a time.

EDIT: Here's sample code. If you run this you'll see both alerts open (0 then 1) after you dismiss '1' you'll see '0' under it. After you dismiss '0' you'll see what I mean - they keyboard briefly closes and opens but no delegate functions are called. If you set i to a value higher than 2, you'll see that the keyboard still closes after dismissing the 2nd alert, but will stay closed until the last alert is dismissed. I also tried opening just 1 UIAlert, and opening the others one at a time from a queue as each one was dismissed, and still noticed that same behavior. Any ideas?

EDIT: After some more digging I found that if I register for the notifications UIKeyboardDidShowNotification and UIKeyboardDidHideNotification they are in fact fired when the keyboard is automatically dismissed and presented. I still would like to know what in the underlying API is causing it to even happen so it can hopefully be avoided.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
// Override point for customization after application launch.
UITextField *textField = [[UITextField alloc] initWithFrame:CGRectMake(0, 100, 320, 48)];
[textField setDelegate:self];
[textField setBackgroundColor:[UIColor redColor]];
[window addSubview:textField];
[textField release];
[self.window makeKeyAndVisible];
return YES;
}

- (BOOL)textFieldShouldReturn:(UITextField *) textField{
NSLog(@"textFieldShouldReturn called with %@", textField);
[textField resignFirstResponder];
return YES;
}


-(void) textFieldDidBeginEditing:(UITextField *)textField 
{
NSLog(@"textFieldDidBeginEditing called with %@", textField);
for (int i=0; i< 2; i++) {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"test" message: [NSString stringWithFormat:@"%d", i] delegate:self cancelButtonTitle:NSLocalizedString(@"OK",@"") otherButtonTitles:nil];
    [alert show];
    [alert release];
}
}

- (BOOL)textFieldShouldEndEditing:(UITextField *)textField
{
NSLog(@"++++ textFieldShouldEndEditing %@", textField);
return YES;
}

-(void) textFieldDidEndEditing:(UITextField *)textField
{
NSLog(@"++++ textFieldDidEndEditing %@", textField);

}

回答1:

the keyboard is only shown when the corresponding UI element is the first responder.. somehow multiple alert views modify the responder chain for a short time. Seems like a framework issue..

I would suggest this workaround:

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
    dispatch_async(dispatch_get_main_queue(), ^{
        /* show new alert view here */
    });
}

EDIT

actually i now think it has to do with the Window hierarchy of the application. UIAlertViews create their own window (at window level UIWindowLevelAlert), make them the key window to recieve touch input and then make the old window key window again upon dismissal. When you show a new alert view on didDismiss, UIKit seems to lose (temporarily) track of key windows and the responder chain..
The fix above of course still applies.

来源：https://stackoverflow.com/questions/7588714/keyboard-dismisses-after-multiple-uialertviews-are-opened

标签

iphone

keyboard

uitextfield

dismiss