在eventFirstResponder或resignFirstResponder的情况下,将对象保持在键盘顶部？

Question

我目前在键盘上有一个UITextField.点击它时,它应该粘在键盘顶部并平稳向上移动.我不知道键盘的确切持续时间和动画类型,所以它真的很颠簸.这就是我所拥有的:

[theTextView resignFirstResponder];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDelegate:self];
[UIView setAnimationDuration:0.25];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
// Frame changes go here (move down 216px)
[UIView commitAnimations];

[theTextView becomeFirstResponder];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDelegate:self];
[UIView setAnimationDuration:0.25];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
// Frame changes go here (move up 216px)
[UIView commitAnimations];

如果有人之前做过这样的事情,我想知道你用来使动画变得平滑的设置,并让它看起来像是"卡在"键盘的顶部.

Answer 1

UIKit UIKeyboardWillShowNotification在显示键盘时以及UIKeyboardWillHideNotification隐藏键盘时发布.这些通知包含正确设置动画的所需信息UITextField.

假设您的UITextField名字叫做"被叫" myTextField.

首先,您需要在某处注册通知.您注册的位置取决于移动的对象myTextField.在我的项目中,该字段的superview负责,因为我从一个笔尖加载我的UI,我在superview中执行awakeFromNib:

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

如果你用a UIViewController来移动字段,你可能想要进行viewWillAppear:animated:.

您应该在您的dealloc或中取消注册viewWillDisappear:animated::

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

当然,这个keyboardWillHideOrShow:方法很棘手.首先,我从通知中提取动画参数:

- (void)keyboardWillHideOrShow:(NSNotification *)note
{
    NSDictionary *userInfo = note.userInfo;
    NSTimeInterval duration = [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    UIViewAnimationCurve curve = [[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];

    CGRect keyboardFrame = [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

该keyboardFrame是全局坐标系统相同.我需要的帧转换到同一坐标系myTextField.frame,并且myTextField.frame是坐标系中myTextField.superview:

    CGRect keyboardFrameForTextField = [self.myTextField.superview convertRect:keyboardFrame fromView:nil];

接下来,我计算要myTextField移动到的帧.新框架的下边缘应该等于键盘框架的上边缘:

    CGRect newTextFieldFrame = self.myTextField.frame;
    newTextFieldFrame.origin.y = keyboardFrameForTextField.origin.y - newTextFieldFrame.size.height;

最后,我myTextField使用键盘使用的相同动画参数设置其新帧的动画:

    [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionBeginFromCurrentState | curve animations:^{
        self.myTextField.frame = newTextFieldFrame;
    } completion:nil];
}

这里全部放在一起:

- (void)keyboardWillHideOrShow:(NSNotification *)note
{
    NSDictionary *userInfo = note.userInfo;
    NSTimeInterval duration = [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    UIViewAnimationCurve curve = [[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];

    CGRect keyboardFrame = [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGRect keyboardFrameForTextField = [self.myTextField.superview convertRect:keyboardFrame fromView:nil];

    CGRect newTextFieldFrame = self.myTextField.frame;
    newTextFieldFrame.origin.y = keyboardFrameForTextField.origin.y - newTextFieldFrame.size.height;

    [UIView animateWithDuration:duration delay:0 options:UIViewAnimationOptionBeginFromCurrentState | curve animations:^{
        self.myTextField.frame = newTextFieldFrame;
    } completion:nil];
}

Answer 2

将文本字段(或包含文本字段的视图)设置为inputAccessoryView您正在编辑的字段.然后它会自动连接到键盘顶部并进行适当的动画制作.