How to toggle a word selection view (change height) in iOS custom keyboard?

Question

I'd to like to add a word selection view similar to the above in an iOS 8 custom keyboard.

1. How can I change the keyboard view rectangle size dynamically? and
2. notify the active app (such as the built-in Messages app) to reposition the input bar correspondingly?

UPDATE: based on this, the height of keyboard is customisable. How can that be possible?

Answer 1

It IS possible to change the size of the keyboard in the current iOS 8

Taken verbatim from the documentation: "In iOS 8.0, you can adjust a custom keyboard’s height any time after its primary view initially draws on screen."

To resize your custom keyboard, add a simple layout constraint.

CGFloat _expandedHeight = 500;
NSLayoutConstraint *_heightConstraint = 
    [NSLayoutConstraint constraintWithItem: self.view 
                                 attribute: NSLayoutAttributeHeight 
                                 relatedBy: NSLayoutRelationEqual 
                                    toItem: nil 
                                 attribute: NSLayoutAttributeNotAnAttribute 
                                multiplier: 0.0 
                                  constant: _expandedHeight];
[self.view addConstraint: _heightConstraint];

For more information look at Apple's prerelease documentation here!