iOS：在 iPad 模式视图中获取键盘点的顶部？

Question

我需要在显示键盘时调整“消息栏”，并且在使用 iPad 模态视图控制器时遇到问题。 “消息栏”在显示时应位于键盘的正上方，然后在键盘隐藏时位于模式的底部（类似于消息应用程序样式）。

问题是我需要根据模态坐标系获得键盘框架的最高点。 我发现这个答案在理论上似乎是正确的，但不起作用（How can I find portion of my view which isn't covered by the keyboard (UIModalPresenationStyleFormSheet)?）：

仅供参考当显示键盘时，主窗口中的键盘框架（即“keyboardFrame”）= (-84.0, 526.0, 768.0, 264.0)。为模态视图控制器坐标系翻译时的键盘框架（即'newSize'）= (-168.0, 292.0, 768.0, 264.0)*

// Convert the keyboard rect into the view controller's coordinate system
// The fromView: nil means keyboardRect is in the main window's coordinate system
let newSize = self.view.convertRect(keyboardFrame, fromView: nil)

// And then this is the part that gets covered!
let keyboardCoveredHeight = self.view.bounds.height - newSize.origin.y
self.messageToolbar.bottomConstraint.constant = -keyboardCoveredHeight

Answer 1

我最终使用熟悉的类别在 iPad 模态视图中获得正确的键盘框架：

- (CGFloat)heightCoveredByKeyboardOfSize:(CGSize)keyboardSize
{
UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
CGRect frameInWindow = [self convertRect:self.bounds toView:nil];
CGRect windowBounds = self.window.bounds;

CGFloat keyboardTop;
CGFloat heightCoveredByKeyboard;

//Determine height of the view covered by the keyboard relative to current rotation

switch (orientation)
{
    case UIInterfaceOrientationLandscapeLeft:
    case UIInterfaceOrientationLandscapeRight:
        keyboardTop = windowBounds.size.height - keyboardSize.height;
        heightCoveredByKeyboard = windowBounds.size.height - frameInWindow.origin.y - keyboardTop;
        break;
    case UIInterfaceOrientationPortraitUpsideDown:
    default:
        keyboardTop = windowBounds.size.height - keyboardSize.height;
        heightCoveredByKeyboard = CGRectGetMaxY(frameInWindow) - keyboardTop;
        break;
}

return MAX(0.0f,heightCoveredByKeyboard);
}

连同 DAKeyboardControl（用于平移）：

    // Use [unowned self] in closure for weak reference
    self.view.addKeyboardPanningWithFrameBasedActionHandler(nil, constraintBasedActionHandler: { [unowned self] (keyboardFrameInView, opening, closing) -> Void in
        if opening
        {
            if UIDevice.isIpad()
            {
                // iPad requires a different method due to use of modal view
                self.messageToolbar.bottomConstraint.constant = -self.view.heightCoveredByKeyboardOfSize(keyboardFrameInView.size)
            }
            else
            {
                self.messageToolbar.bottomConstraint.constant = -keyboardFrameInView.size.height
            }
        }

        if closing
        {
            self.messageToolbar.bottomConstraint.constant = 0
        }

        self.view.updateConstraintsIfNeeded()
        self.view.layoutIfNeeded()
    })

Answer 2

可以在keyboardDidShowNotification上以这种方式计算精确的重叠

let parentRelativeFrame = view.convert(view.frame, to: nil)
let viewBottomVerticalOffset = parentRelativeFrame.origin.y + parentRelativeFrame.height
let overlap = viewBottomVerticalOffset - keyboardFrame.origin.y

Answer 3

我认为您遇到了两个问题之一（可能两者都有）：

1. 在 iOS 8 中，您必须从屏幕坐标空间转换键盘的矩形
2. 在 iPad 上，当显示键盘时，工作表视图有时会向上移动一点，这种情况发生在键盘显示之后，因此您需要再次计算结果在viewWillLayoutSubviews

这里是a sample project that does what you want。

为了后代，这里是有趣的源代码：

class TypingViewController: UIViewController {

    var keyboardHoverView: UIView! // your keyboard toolbar or whatever
    var lastKeyboardFrame : CGRect! // whenever you get a frame update, store it here

    override func viewDidLoad() {
        super.viewDidLoad()

        createKeyboardHoverView()
        observeKeyboard()
    }

    func createKeyboardHoverView() {
        // make your keyboard toolbar
        keyboardHoverView = view
    }

    func observeKeyboard() {
        NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name: UIKeyboardWillHideNotification, object: nil)
    }

    func keyboardWillShow(notification : NSNotification) {
        let dict = notification.userInfo!
        let frameValue = dict[UIKeyboardFrameEndUserInfoKey] as! NSValue
        lastKeyboardFrame = frameValue.CGRectValue()

        moveKeyboardView()
    }

    func keyboardWillHide(notification : NSNotification) {
        moveKeyboardView()
    }

    override func viewWillLayoutSubviews() {
        // this moves the view again, in case the modal view has shifted up
        moveKeyboardView()
    }

    func moveKeyboardView() {
        if lastKeyboardFrame != nil {
            // this conversion is used in iOS 8 and differs from most online tutorials
            let frameInThisView = self.view.convertRect(lastKeyboardFrame, fromCoordinateSpace: view.window!.screen.coordinateSpace)

            var newRect = keyboardHoverView.frame
            newRect.origin.y = frameInThisView.origin.y - CGRectGetHeight(newRect)
            keyboardHoverView.frame = newRect

            println("Setting rect: \(newRect)")
        }
    }
}