UIAlertController dismiss is slow

问题

After iOS 8, changing my implementation to UIAlertController instead of UIAlertView is giving me some headaches.

The dismissal takes around a full second before the UI becomes responsive after clicking a button. It means users think there's something wrong.

Am I the only one suffering from this? It's across several apps, and true for an implementation as simple as this. I tried this in a new blank project.

- (IBAction)showAlertView {

    [[[UIAlertView alloc] initWithTitle:@"test" message:@"test" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil] show];
}

-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {

    NSLog(@"this is fast");
}

-(IBAction)showAlert {

    UIAlertController *controller = [UIAlertController alertControllerWithTitle:@"test" message:@"test" preferredStyle:UIAlertControllerStyleAlert];

    [controller addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {

        NSLog(@"this is slow");

    }]];

    [self presentViewController:controller animated:NO completion:nil];

}

Clicking the button gives around a 1-second delay before anything is printed to the console. Presentation of the alert is not delayed at all.

Edit: By closer timing it's probably more like 700ms, so not a full second, but still way too long for something that should be instantaneous.

回答1:

I know it's an old question but I had the same problem and adding this in the ViewController presenting the UIAlertController solved it for me:

- (BOOL)canBecomeFirstResponder {
    return YES;
}

Swift version:

override func canBecomeFirstResponder() -> Bool {
    return true
}

回答2:

Sadly, overriding canBecomeFirstResponder did not help us.

What did help us was to call resignFirstResponder on any possible responders in the view controller BEFORE showing the alert.

For some reason, if a text field was a first responder, it looks like it would try to go through the view hierarchy looking for the next responder. If no text fields had any focus, the delay disappeared.

来源：https://stackoverflow.com/questions/37165632/uialertcontroller-dismiss-is-slow

标签

ios

objective-c

uialertcontroller