在输入附件视图中显示带有 UITextField 的键盘

Question

我有一个 buttonA，当单击 buttonA 时，我希望键盘在 inputAccessoryView 中显示一个 UITextField。有没有办法手动显示键盘并设置 inputAccessoryView 而没有最初的 UITextField？

谢谢。

Answer 1

如果没有可以成为第一响应者的对象，您将无法召唤键盘。有两种解决方法：

• 子类化 UIView 并在其中实现 UIKeyInput 协议。例如：

  在您的 .h 文件中：

  @interface InputObject : UIView<UIKeyInput>
  @property (nonatomic, copy) NSString *text;
  @property (nonatomic, strong) UIView *inputAccessoryView; // You must override inputAccessoryView , since it's readonly by default
  @end
  

  在您的 .m 文件中，实现协议：

  - (BOOL)canBecomeFirstResponder
  {
      return YES;
  }
  
  - (BOOL)hasText
  {
      return [self.text length];
  }
  
  - (void)insertText:(NSString *)text
  {
      NSString *selfText = self.text ? self.text : @"";
      self.text = [selfText stringByAppendingString:text];
      [[NSNotificationCenter defaultCenter] postNotificationName:kInputObjectTextDidChangeNotification object:self];
  }
  
  - (void)deleteBackward
  {
      if ([self.text length] > 0)
          self.text = [self.text substringToIndex:([self.text length] - 1)];
      else
          self.text = nil;
      [[NSNotificationCenter defaultCenter] postNotificationName:kInputObjectTextDidChangeNotification object:self];
  }
  

假设你想在-viewDidAppear: 中召唤键盘，代码如下：

    - (void)viewDidLoad
    {
        [super viewDidLoad];
        // inputObject and textField are both your ivars in your view controller
        inputObject = [[InputObject alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
        textField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 100, 30)];
        inputObject.inputAccessoryView = textField;
        [self.view addSubview:inputObject];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(inputObjectTextDidChange:) name:kInputObjectTextDidChangeNotification object:nil];

    }

    - (void)viewDidAppear:(BOOL)animated
    {
        [super viewDidAppear:animated];
        [inputObject becomeFirstResponder]; // This will summon the keyboard
    }

然后在你的视图控制器中实现通知选择器：

    - (void)inputObjectTextDidChange:(NSNotification *)notification
    {
        // Just set the text here. notification.object is actually your inputObject.
        textField.text = ((InputObject *)(notification.object)).text;
    }

这可能是您所说的“在最初没有 UITextField 的情况下设置 inputAccessoryView”的意思

• 另一种解决方法是通过仔细安排其动画让 textField “假装”为inputAccessoryView。但是此解决方案需要您的 textField 成为第一响应者。

首先，您观察-viewDidLoad 中的键盘事件：

    - (void)viewDidLoad
    {
        [super viewDidLoad];
        // Init the textField and add it as a subview of self.view
        textField = [[UITextField alloc] init];
        textField.backgroundColor = [UIColor redColor];
        [self.view addSubview:textField];

        // Register keyboard events
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShowNotification:) name:UIKeyboardWillShowNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHideNotification:) name:UIKeyboardWillHideNotification object:nil];
    }

其次，将你的textField的框架设置为-viewWillAppear:，以保证其框架不受自动调整大小的影响：

    - (void)viewWillAppear:(BOOL)animated
    {
        [super viewWillAppear:animated];
        textField.frame = CGRectMake(0, CGRectGetMaxY(self.view.bounds), CGRectGetWidth(self.view.bounds), 50);
    }

然后，安排你的textField 动画，让它与键盘动画同步。您的键盘通知选择器可能是这样的：

    - (void)keyboardWillShowNotification:(NSNotification *)notification
    {
        NSDictionary *userInfo = notification.userInfo;
        UIViewAnimationCurve curve = [[userInfo valueForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];
        CGFloat duration = [[userInfo valueForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue];
        CGRect keyboardFrame = [[userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
        keyboardFrame = [self.view convertRect:keyboardFrame toView:self.view];

        [UIView animateWithDuration:duration delay:0.0f options:(UIViewAnimationOptions)curve animations:^{
            CGRect textFieldFrame = textField.frame;
            textFieldFrame.origin.y = keyboardFrame.origin.y - CGRectGetHeight(textFieldFrame);
            textField.frame = textFieldFrame;
        }completion:nil];
    }

    - (void)keyboardWillHideNotification:(NSNotification *)notification
    {
        NSDictionary *userInfo = notification.userInfo;
        UIViewAnimationCurve curve = [[userInfo valueForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];
        CGFloat duration = [[userInfo valueForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue];
        [UIView animateWithDuration:duration delay:0.0f options:(UIViewAnimationOptions)curve animations:^{
            textField.frame = CGRectMake(0, CGRectGetMaxY(self.view.bounds), CGRectGetWidth(self.view.bounds), 50);
        }completion:nil];
    }

最后调用[textField becomeFirstResponder]触发动画。

Answer 2

另一种解决方案是将这些方法添加到您的 UIViewController 实现中：

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

- (BOOL)canBecomeFirstResponder {
    return YES;
}

- (UIView *)inputAccessoryView {
    if (!_textField) {
        _textField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
        _textField.backgroundColor = [UIColor whiteColor];
        _textField.delegate = self;
    }
    return _textField;
}

#pragma mark - UITextFieldDelegate

- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    [textField resignFirstResponder];
    return YES;
}

并将_textField 变量添加到您的界面：

@interface ViewController : UIViewController <UITextFieldDelegate> {
    UITextField *_textField;
}
@end

Answer 3

解决这个问题的一个hacky方法是在视图中有一个UITextField但隐藏，然后在它上面调用[textfield becomeFirstResponder]。

我刚刚测试了它，这很有效

UITextField * randofield = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 0, 0)];
[self.view addSubview:randofield];
// doesn't have to be hidden... but to be safe.
randofield.hidden = YES;
[randofield becomeFirstResponder];

你必须让它成为视图的子视图，否则这将不起作用。

Answer 4

使用自动布局约束的 Swift 版本基于刘耀东的回答。

要求您在屏幕底部和文本视图之间设置垂直空间约束。请注意，设置偏移量必须发生在动画上下文之外，并且只有布局发生在动画上下文中。

@IBOutlet weak var textViewBottomOffsetConstraint: NSLayoutConstraint!

override public func viewDidLoad() {
    super.viewDidLoad()
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(keyboardWillShow(_:)), name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(keyboardWillHide(_:)), name: UIKeyboardWillHideNotification, object: nil)
}

func keyboardWillHide(notification: NSNotification) {
    guard let userInfo = notification.userInfo else {
        return
    }

    animateTextFieldOffset(0, userInfo: userInfo)
}

func keyboardWillShow(notification: NSNotification) {
    guard let userInfo = notification.userInfo, var keyboardFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.CGRectValue() else {
        return
    }

    keyboardFrame = view.convertRect(keyboardFrame, toView: view)

    animateTextFieldOffset(keyboardFrame.size.height, userInfo: userInfo)
}

func animateTextFieldOffset(offset: CGFloat, userInfo: [NSObject: AnyObject] ){
    guard let animationCurveInt = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? Int, let animationCurve = UIViewAnimationCurve(rawValue:animationCurveInt) else { return }

    guard let animationDuration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Double else { return }

    self.loginViewBottomOffsetConstraint.constant = offset

    UIView.beginAnimations(nil, context: nil)
    UIView.setAnimationDuration(animationDuration)
    UIView.setAnimationCurve(animationCurve)
    UIView.setAnimationBeginsFromCurrentState(true)
    self.view.layoutIfNeeded()
    UIView.commitAnimations()
}