Incorrect Keyboard Extension height after rotation

问题

I have iOS custom keyboard that changes height when it rotates.

My code works fine 95% times... But in some cases (see below) the height is not changed when rotated to landscape - portrait height is kept.

Issue can be reproduced with this (almost) minimal code - create new Keyboard Extension target and copy this code to KeyboardViewController:

class KeyboardViewController: UIInputViewController {
    private var orangeView = UIView()
    private var heightConstraint: NSLayoutConstraint!
    @IBOutlet var nextKeyboardButton: UIButton!

    override func updateViewConstraints() {
        super.updateViewConstraints()
        let screenSize = UIScreen.mainScreen().bounds.size
        let screenH = screenSize.height
        let screenW = screenSize.width
        let isLandscape = !(self.view.frame.size.width == screenW * ((screenW < screenH) ? 1 : 0) + screenH * ((screenW > screenH) ? 1 : 0))
        let desiredHeight: CGFloat = isLandscape ? 193 : 252
        if heightConstraint.constant != desiredHeight {
            heightConstraint!.constant = desiredHeight
            orangeView.frame = CGRect(x: 0, y: 0, width: screenW, height: isLandscape ? 193 : 252)
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        nextKeyboardButton = UIButton(type: .System)
        nextKeyboardButton.setTitle("Next Keyboard", forState: .Normal)
        nextKeyboardButton.sizeToFit()
        nextKeyboardButton.translatesAutoresizingMaskIntoConstraints = false
        nextKeyboardButton.addTarget(self, action: "advanceToNextInputMode", forControlEvents: .TouchUpInside)
        heightConstraint = NSLayoutConstraint(item:self.inputView!, attribute:.Height, relatedBy:.Equal, toItem:nil, attribute:.NotAnAttribute, multiplier: 0.0, constant: 0) //preparing heightConstraint
        heightConstraint?.priority = 999
        orangeView.backgroundColor = UIColor.orangeColor()
        view.addSubview(orangeView)
        view.addSubview(self.nextKeyboardButton)
        let nextKeyboardButtonLeftSideConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1.0, constant: 0.0)
        let nextKeyboardButtonBottomConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Bottom, relatedBy: .Equal, toItem: self.view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
        view.addConstraints([nextKeyboardButtonLeftSideConstraint, nextKeyboardButtonBottomConstraint])
    }

    override func viewWillAppear(animated: Bool) {
        if self.view.constraints.filter({c in c == self.heightConstraint}).isEmpty {
            self.view.addConstraint(heightConstraint)
        }
        view.setNeedsUpdateConstraints() //ensures that updateViewConstraints always gets called at least once
        super.viewWillAppear(animated)
    }
}

For more info on how it works see this and this answer.

When you run the keyboard it will probably work fine - it is slightly higher and after rotation the orange view covers the whole keyboard:

However you might also get this (portrait height is kept after rotation):

Steps to reproduce the isue (with code above):

Open keyboard in Messages app, rotate landscape and back
If you did not see the issue kill Messages app (press home button 2x -> swipe messages up)
Open messages again, rotate landscape and back
You might need to repeat steps 1-3 few times to see the issue (usually no more than 2-4 times)

What I know:

If you see the issue you will keep seing it until keyboard is hidden and re-displayed
If you see the issue hide and re-display the keyboard withing same app - the issue always disapears
The issue might appear again only after killing and restarting the hosting app
Debuger shows that heightConstraint!.constant is 193 but both view.frame.height and view.window?.frame.height are still 253 (changing frame directly does not fix it)

What I have tried:

Instead of just setting the constraint heightConstraint!.constant = desiredHeight first remove it from view, set new value and then re-add it
I verified that heightConstraint!.constant is always changed when it should be

How do I fix or workaround this issue? There has to be a solution because SwiftKey does not have this issue.

回答1:

I faced a similar issue with a keyboard extension -- on iPhone 6+ models, it always failed to set its height correctly on rotations the first time the keyboard was invoked in an app, and occasionally on iPhone 6 and other iPhone models.

I eventually found a solution, though it has its own drawbacks.

Firstly, the documentation states that

In iOS 8.0, you can adjust a custom keyboard’s height any time after its primary view initially draws on screen.

You're setting the height constraint in -[UIViewController viewWillAppear:], which, under a strict interpretation of the documentation, is too early. If you set it in -[UIViewController viewDidAppear:], the problem that you're currently having should be solved.

However, you may then find that your height adjustment is visually jarring, as it is occurring after the keyboard is appearing.

I have no idea how SwiftKey manages to set their height (seemingly) before the keyboard appears and avoid this issue.

来源：https://stackoverflow.com/questions/36145450/incorrect-keyboard-extension-height-after-rotation

标签

ios

iphone

swift

ios-app-extension

custom-keyboard