Autolayout约束 - 键盘

Question

我试图平滑地制作一个具有自动布局约束的桌面视图.我在我的.h中引用了约束"keyboardHeight",并在IB中将其链接起来.我想要做的就是在弹出窗口时用键盘为表格视图设置动画.这是我的代码:

- (void)keyboardWillShow:(NSNotification *)notification
{
    NSDictionary *info = [notification userInfo];
    NSValue *kbFrame = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
    NSTimeInterval animationDuration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    CGRect keyboardFrame = [kbFrame CGRectValue];
    CGFloat height = keyboardFrame.size.height;

    [UIView animateWithDuration:animationDuration animations:^{
        self.keyboardHeight.constant = -height;
        [self.view setNeedsLayout];
    }];
}

事情是动画块是瞬时的,我看到在键盘完成动画之前出现了空格.所以基本上我看到视图的白色背景,因为键盘是动画.只要键盘是动画,我就无法使动画持续.

我接近这个错误的方式吗？提前致谢!

Answer 1

试试这种方式:

self.keyboardHeight.constant = -height;
[self.view setNeedsUpdateConstraints];

[UIView animateWithDuration:animationDuration animations:^{
   [self.view layoutIfNeeded];
}];

记住这种模式,因为这应该是更新基于约束的布局的正确方法(根据WWDC).NSLayoutConstraint只要您打电话setNeedsUpdateConstraints,您也可以添加或删除s .

Answer 2

如果您正在使用UITableViewController,iOS应自动调整键盘大小以调整contentInsets.但是如果你的tableView在UIViewController中,你可能想要使用它:

KeyboardLayoutConstraint在春天框架.到目前为止我找到的最简单的解决方案.

Answer 3

尝试下一个代码.在这种情况下,表格视图位于屏幕的底部边缘.

- (void)keyboardWillShow:(NSNotification *)notification { // UIKeyboardWillShowNotification

    NSDictionary *info = [notification userInfo];
    NSValue *keyboardFrameValue = [info objectForKey:UIKeyboardFrameEndUserInfoKey];
    NSTimeInterval animationDuration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    CGRect keyboardFrame = [keyboardFrameValue CGRectValue];

    BOOL isPortrait = UIDeviceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation);
    CGFloat keyboardHeight = isPortrait ? keyboardFrame.size.height : keyboardFrame.size.width;

    // constrBottom is a constraint defining distance between bottom edge of tableView and bottom edge of its superview
    constrBottom.constant = keyboardHeight; 
    // or constrBottom.constant = -keyboardHeight - in case if you create constrBottom in code (NSLayoutConstraint constraintWithItem:...:toItem:...) and set views in inverted order

    [UIView animateWithDuration:animationDuration animations:^{
        [tableView layoutIfNeeded];
    }];
}


- (void)keyboardWillHide:(NSNotification *)notification { // UIKeyboardWillHideNotification

    NSDictionary *info = [notification userInfo];
    NSTimeInterval animationDuration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];

    constrBottom.constant = 0;
    [UIView animateWithDuration:animationDuration animations:^{
        [tableView layoutIfNeeded];
    }];
}