这只是@arlomedia对答案的增强，我所做的是观看willshow和didShow。
willShow我用来移动我的文本视图到适当的位置，使其移动速度与键盘相同。
我使用didShow使用上述技术检查键盘的外观大小，并相应地隐藏/显示附件InputView。

重要的是我还将该视图设置为默认隐藏，并且当收到willHide事件时，它将再次隐藏。

- (void) addKeyboardObserver {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardDidShow:) name:UIKeyboardDidShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardHidden:) name:UIKeyboardWillHideNotification object:nil];
}

- (void) removeKeyboardObserver {
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

- (void)keyboardWillShow:(NSNotification*)notification {
    CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;

    // If we're on iOS7 or earlier and landscape then the height is in the
    // width.
    //
    if ((IS_LANDSCAPE == YES) && (IS_IOS8_OR_LATER == NO)) {
        keyboardSize.height = keyboardSize.width;
    }

    NSNumber *rate = notification.userInfo[UIKeyboardAnimationDurationUserInfoKey];

    CGRect textFieldFrame = self.textField.frame;
    textFieldFrame.origin.y = ([Util screenHeight] - keyboardSize.height) - textFieldFrame.size.height - [Util scaledHeight:10.0];

    // Move the text field into place.
    //
    [UIView animateWithDuration:rate.floatValue animations:^{
        self.answerTextField.frame = textFieldFrame;
    }];

    keyboardShown = YES;
}

- (void)keyboardDidShow:(NSNotification*)notification {
    CGRect keyboardBeginFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue];
    CGRect keyboardEndFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGSize keyboardSize = keyboardBeginFrame.size;

    // If we're on iOS7 or earlier and landscape then the height is in the
    // width.
    //
    if ((IS_LANDSCAPE == YES) && (IS_IOS8_OR_LATER == NO)) {
        keyboardSize.height = ABS(keyboardBeginFrame.origin.x - keyboardEndFrame.origin.x); // the keyboard will move by an amount equal to its height when it appears; ABS is needed for upside-down orientations
    } else {
        keyboardSize.height = ABS(keyboardBeginFrame.origin.y - keyboardEndFrame.origin.y); // the keyboard will move by an amount equal to its height when it appears; ABS is needed for upside-down orientations
    }

    NSNumber *rate = notification.userInfo[UIKeyboardAnimationDurationUserInfoKey];

    [UIView animateWithDuration:rate.floatValue animations:^{
        if (keyboardSize.height <= self.accessoryBar.frame.size.height) {
            self.textField.inputAccessoryView.hidden = YES;
            self.answerTextField.inputAccessoryView.userInteractionEnabled = NO;
        } else {
            self.textField.inputAccessoryView.hidden = NO;
            self.answerTextField.inputAccessoryView.userInteractionEnabled = YES;
        }
    }];

    keyboardShown = YES;
}

- (void)keyboardHidden:(NSNotification*)notification {

    NSNumber *rate = notification.userInfo[UIKeyboardAnimationDurationUserInfoKey];

    // Remove/hide the accessory view so that next time the text field gets focus, if a hardware
    // keyboard is used, the accessory bar is not shown.
    //
    [UIView animateWithDuration:rate.floatValue animations:^{
        self.textField.inputAccessoryView.hidden = YES;
        self.answerTextField.inputAccessoryView.userInteractionEnabled = NO;
    }];

    keyboardShown = NO;
}

注意编辑以添加对userInteractionEnabled的更改，以便隐藏的附件视图不会吃掉点击。

IIRC，当软键盘出现时，视图不会自动调整大小。我正在通过一个由UIKeyboardDidShow通知触发的keyboardDidShow方法来调整视图大小。因此，在该方法中检测硬件和软件键盘应该足够了，然后您可以跳过表格调整大小并隐藏输入辅助视图（或者调整表格大小以适应输入辅助视图，如果您更喜欢使其可见）。
无论是否存在硬件键盘，为了正确地调整视图大小，我修改了this answer中的代码：

- (void)keyboardDidShow:(NSNotification *)aNotification {
    CGRect keyboardBeginFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue];
    CGRect keyboardEndFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    float keyboardHeight = ABS(keyboardBeginFrame.origin.y - keyboardEndFrame.origin.y); // the keyboard will move by an amount equal to its height when it appears; ABS is needed for upside-down orientations

    // now you can resize your views based on keyboardHeight
    // that will be the height of the inputAccessoryView if a hardware keyboard is present
}

如果你想让inputAccessoryView保持可见，这就是你所需要的。要隐藏它，我认为你需要设置一个示例变量，这样你就可以在keyboardDidShow中访问它：

UIView *currentInputAccessoryView;

- (void)textFieldDidBeginEditing:(UITextField *)textField {
    self.currentInputAccessoryView = textField.inputAccessoryView;
}

- (void)textViewDidBeginEditing:(UITextView *)textView {
    self.currentInputAccessoryView = textView.inputAccessoryView;
}

- (void)keyboardDidShow:(NSNotification *)aNotification {
    CGRect keyboardBeginFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue];
    CGRect keyboardEndFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    float keyboardHeight = ABS(keyboardBeginFrame.origin.y - keyboardEndFrame.origin.y); // the keyboard will move by an amount equal to its height when it appears; ABS is needed for upside-down orientations

    if (keyboardHeight == 44) {
        self.currentInputAccessoryView.hidden = YES;
        keyboardHeight = 0;
    }

    // now you can resize your views based on keyboardHeight
    // that will be 0 if a hardware keyboard is present
}

我解决这个问题的最后一个方法是简单地为UIKeyboardWillShowNotification添加一个观察者...

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillShow:)
                                             name:UIKeyboardWillShowNotification object:nil];

..并隐藏先前存储在示例变量中的inputAccessoryView。

// Called when the UIKeyboardWillShowNotification is sent.
- (void)keyboardWillShow:(NSNotification*)notification
{
    NSLog(@"keyboardWillShow");

    // get the frame end user info key
    CGRect kbEndFrame = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

    // calculate the visible portion of the keyboard on the screen
    CGFloat height = [[UIScreen mainScreen] bounds].size.height - kbEndFrame.origin.y;

    // check if there is a input accessorry view (and no keyboard visible, e.g. hardware keyboard)
    if (self.activeTextField && height <= self.activeTextField.inputAccessoryView.frame.size.height) {

        NSLog(@"hardware keyboard");

        self.activeTextField.inputAccessoryView.hidden = YES;
    } else {

        NSLog(@"software keyboard");

        self.activeTextField.inputAccessoryView.hidden = NO;
    }
}

原来这个问题是由我在getter方法中动态创建我的自定义UITextField子类的inputAccessoryView引起的。我无意中在每次调用getter时重新创建了视图，而不是在惰性示例化中重用示例变量。这导致我对视图的所有赋值都被忽略，因为显然getter方法将被多次调用当访问文本字段时，键盘显示，因此视图在我的分配后被覆盖。通过将视图保存到示例变量来重用视图修复了此问题。

这是一个旧的线程，但截至iOS 14，我们现在有适当的API通过GameController框架使用GCKeyboard和GCKeyboardDidConnect/GCKeyboardDidDisconnect通知跟踪硬件键盘。
在这个隐藏和显示inputAccessoryView的特殊情况下，您可以执行如下操作：

import GameController

class ViewController: UIViewController {
    ...
    var isHardwareKeyboardConnected: Bool {
        didSet {
            enableInputAccessoryIfNeeded()
        }
    }

    func enableInputAccessoryIfNeeded() {
        textField.inputAccessoryView = isHardwareKeyboardConnected ? nil : textFielInputAccessoryView
        textField.reloadInputViews()
    }

    init() {
        isHardwareKeyboardConnected = GCKeyboard.coalesced != nil
        super.init(nibName: nil, bundle: nil)
        startObservingHardwareKeyboard()
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        enableInputAccessoryIfNeeded()
    }

    func startObservingHardwareKeyboard() {
        NotificationCenter.default.addObserver(self, selector: #selector(hardwareKeyboardDidConnect), name: .GCKeyboardDidConnect, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(hardwareKeyboardDidDisconnect), name: .GCKeyboardDidDisconnect, object: nil)
    }

    @objc func hardwareKeyboardDidConnect(_ notification: Notification) {
        print("[Keyboard] Hardware keyboard did connect")
        isHardwareKeyboardConnected = true
    }

    @objc func hardwareKeyboardDidDisconnect(_ notification: Notification) {
        print("[Keyboard] Hardware keyboard did disconnect")
        isHardwareKeyboardConnected = false
    }
}