如何同时解除UIAlertController和键盘？

Question

我创建了一个带有a的注册表单,UIAlertController并使用该方法addTextFieldWithConfigurationHandler添加文本字段.但是有一点问题.

当表单出现时,键盘和模态会以平滑的动画显示.关闭表单时,模态首先消失,然后键盘消失.这使键盘突然下降.

如何使模态和键盘优雅地消失？

lazy var alertController: UIAlertController = { [weak self] in
    let alert = UIAlertController(title: "Alert", message: "This is a demo alert", preferredStyle: .Alert)
    alert.addTextFieldWithConfigurationHandler { textField in
        textField.delegate = self
    }
    alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
    return alert
}()

@IBAction func alert() {
    presentViewController(alertController, animated: true, completion: nil)
}

func textFieldShouldReturn(textField: UITextField) -> Bool {
    alertController.dismissViewControllerAnimated(true, completion: nil)
    return true
}

Answer 1

您可以将视图控制器或其他对象设置为转换UIAlertController(alert.transitioningDelegate)的委托,并制作用于解除的自定义动画.代码示例:

@interface ViewController () <UIViewControllerTransitioningDelegate, UIViewControllerAnimatedTransitioning, UITextFieldDelegate>
@property (assign, nonatomic) NSTimeInterval keyboardAnimationDuration;
@property (assign, nonatomic) CGFloat keyboardHeight;
@property (nonatomic, strong) UIAlertController *alertController;
@property (nonatomic,strong) id <UIViewControllerTransitioningDelegate> transitioningDelegateForAlertController;
@end

@implementation ViewController

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)viewDidLoad {
    [super viewDidLoad];
    [self subscribeForKeyboardNotification];
}

#pragma mark - Keyboard notifications

- (void)subscribeForKeyboardNotification {
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillAppear:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
}

- (void)keyboardWillAppear:(NSNotification *)notification {
    self.keyboardAnimationDuration = [notification.userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    self.keyboardHeight = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size.height;
}

#pragma mark - IBAction

- (IBAction)showAlertButtonPressed:(id)sender {
    [self showAlert];
}

- (void)showAlert {
    self.alertController = [UIAlertController alertControllerWithTitle:@"Alert"
                                                                             message:@"This is a demo alert"
                                                                      preferredStyle:UIAlertControllerStyleAlert];
    __weak typeof(self) weakSelf = self;
    [self.alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) {
        textField.delegate = weakSelf;
    }];
    self.transitioningDelegateForAlertController = self.alertController.transitioningDelegate;
    self.alertController.transitioningDelegate = self;
    [self.alertController addAction:[UIAlertAction actionWithTitle:@"Ok"
                                                        style:UIAlertActionStyleCancel
                                                      handler:nil]];
    [self presentViewController:self.alertController animated:YES completion:nil];
}

#pragma mark - UITextFieldDelegate

- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    [self.alertController dismissViewControllerAnimated:YES completion:nil];
    return YES;
}

#pragma mark - UIViewControllerTransitioningDelegate

- (id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented
                                                                   presentingController:(UIViewController *)presenting
                                                                       sourceController:(UIViewController *)source {
    return [self.transitioningDelegateForAlertController animationControllerForPresentedController:presented
                                                                          presentingController:presenting
                                                                              sourceController:source];
}

- (id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {
    return self;
}

#pragma mark - UIViewControllerAnimatedTransitioning

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext {
    return self.keyboardAnimationDuration ?: 0.5;
}

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *destination = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    if ([destination isBeingPresented])
        [self animatePresentation:transitionContext];
    else
        [self animateDismissal:transitionContext];
}

- (void)animatePresentation:(id <UIViewControllerContextTransitioning>)transitionContext {
    NSTimeInterval transitionDuration = [self transitionDuration:transitionContext];
    UIViewController *fromController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *container = transitionContext.containerView;
    fromController.view.frame = container.bounds;
    toController.view.frame = container.bounds;
    toController.view.alpha = 0.0f;
    [container addSubview:toController.view];
    [fromController beginAppearanceTransition:NO animated:YES];
    [UIView animateWithDuration:transitionDuration
                     animations:^{
                         toController.view.alpha = 1.0;
                     }
                     completion:^(BOOL finished) {
                         [fromController endAppearanceTransition];
                         [transitionContext completeTransition:YES];
                     }];
}

- (void)animateDismissal:(id <UIViewControllerContextTransitioning>)transitionContext {
    NSTimeInterval transitionDuration = [self transitionDuration:transitionContext];
    UIViewController *fromController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    [toController beginAppearanceTransition:YES animated:YES];
    [UIView animateWithDuration:transitionDuration
                     animations:^{
                         fromController.view.alpha = 0.0;
                         [fromController.view endEditing:YES];
                         CGRect frame = fromController.view.frame;
                         frame.origin.y += self.keyboardHeight / 2;
                         fromController.view.frame = frame;
                     }
                     completion:^(BOOL finished) {
                         [toController endAppearanceTransition];
                         [transitionContext completeTransition:YES];
                     }];
}

@end

结果:

PS:我使用旧警报转换代表进行演示,因为我无法重现原始动画.因此animatePresentation:从不使用方法.

Answer 2

我遇到了完全相同的问题并偶然找到了解决方案.你可能不再需要这个,但为了像我这样的其他人,这里是答案:

迅速:

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

Objective-C的:

- (BOOL)canBecomeFirstResponder {
    return true;
}

只需在处理警报的视图控制器中添加此代码即可.只在swift中测试过.