iOS: Get top of keyboard point in iPad modal view? - ios

Question

I need to adjust a 'message bar' when the keyboard is shown and am having issues when using iPad modal view controller. The 'message bar' should sit right on top of the keyboard when it is shown, and then at the bottom of the modal when the keyboard is hidden (a la Messages app style).
The problem is I need to get the top most point of the keyboard's frame in terms of the Modal's coordinate system.
I found this answer that theoretically seems correct, but doesn't work (How can I find portion of my view which isn't covered by the keyboard (UIModalPresenationStyleFormSheet)?):
FYI When the keyboard is shown, the keyboard's frame in the main window (i.e. 'keyboardFrame') = (-84.0, 526.0, 768.0, 264.0). The keyboard's frame when translated for the modal view controller coordinate system (i.e. '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

I ended up using a familiar category to get the proper keyboard frame in a iPad modal view:
- (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);
}
along with DAKeyboardControl (for panning):
// 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

It is possible to calculate exact overlap this way, on keyboardDidShowNotification
let parentRelativeFrame = view.convert(view.frame, to: nil)
let viewBottomVerticalOffset = parentRelativeFrame.origin.y + parentRelativeFrame.height
let overlap = viewBottomVerticalOffset - keyboardFrame.origin.y

Answer 3

I think you're running into one of two problems (maybe both):
In iOS 8, you have to convert the keyboard's rect from the screen's coordinate space
On iPad, the sheet views sometimes move up a bit when the keyboard is displayed, which happens after the keyboard is shown, so you need to calculate the results again in viewWillLayoutSubviews
Here's a sample project that does what you want.
For posterity, here's the interesting source code:
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)")
}
}
}