Resize the UITextView when keyboard appears

In viewWillAppear method, add the following:

- (void) viewWillAppear:(BOOL)paramAnimated{
    [super viewWillAppear:paramAnimated];

    [[NSNotificationCenter defaultCenter] 
        addObserver:self 
           selector:@selector(handleKeyboardDidShow:) 
               name:UIKeyboardDidShowNotification object:nil];

    [[NSNotificationCenter defaultCenter]
        addObserver:self
           selector:@selector(handleKeyboardWillHide:)     
               name:UIKeyboardWillHideNotification object:nil];    
}

Then implement the two methods of the notification center, like this:

- (void) handleKeyboardDidShow:(NSNotification *)paramNotification{

    NSValue *keyboardRectAsObject =
        [[paramNotification userInfo] 
            objectForKey:UIKeyboardFrameEndUserInfoKey];

    CGRect keyboardRect = CGRectZero;
    [keyboardRectAsObject getValue:&keyboardRect];

    yourTextView.contentInset =
        UIEdgeInsetsMake(0.0f,
                         0.0f,
                         keyboardRect.size.height,
                         0.0f);
}

And the other one like:

- (void) handleKeyboardWillHide:(NSNotification *)paramNotification{

    yourTextView.contentInset = UIEdgeInsetsZero;
}

It will work for all devices ;)

Swift / Modified Version

Using the above, I made some adjustments to use NSLayoutConstraint's changing the height constant property when the keyboard shows and hides. This also works if you rotate the device.

1. Set up TextView Constraints

Then control drag an outlet from you height constraint to the class.

2. Add The Following

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)

        NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(SkillDescriptionViewController.keyboardWillShowHandle(_:)), name: UIKeyboardDidShowNotification, object: nil)

        NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(SkillDescriptionViewController.keyboardWillHideHandle), name: UIKeyboardWillHideNotification, object: nil)

    }


    func keyboardWillShowHandle(note:NSNotification) {
        guard let keyboardRect = note.userInfo![UIKeyboardFrameEndUserInfoKey] as? NSValue else { return }
        let kbFrame = keyboardRect.CGRectValue()
        tvHeight.constant = -kbFrame.height
        view.layoutIfNeeded()
    }

    func keyboardWillHideHandle() {
        tvHeight.constant = 0
        view.layoutIfNeeded()
    }

Swift 5 solution based on answers above

Notification API has changed (20190707) as well as how to use #selector

The solution here can be used when the keyboard pop covers UITextView which causes user unable to see the text been edited.

import UIKit

class DCNodeLogEntryViewController: UIViewController {
    @IBOutlet weak var textViewNodeLogEntry: UITextView!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        NotificationCenter.default.addObserver(
            self,
            selector: #selector(DCNodeLogEntryViewController.handleKeyboardDidShow(notification:)),
            name: UIResponder.keyboardDidShowNotification,
            object: nil
        )

        NotificationCenter.default.addObserver(
            self,
            selector: #selector(DCNodeLogEntryViewController.handleKeybolardWillHide),
            name: UIResponder.keyboardWillHideNotification,
            object: nil
        )
    }

    @objc func handleKeyboardDidShow(notification: NSNotification) {
        guard let keyboardRect = notification
            .userInfo![UIResponder.keyboardFrameEndUserInfoKey]
            as? NSValue else { return }

        let frameKeyboard = keyboardRect.cgRectValue

        textViewNodeLogEntry.contentInset = UIEdgeInsets(
            top: 0.0,
            left: 0.0,
            bottom: frameKeyboard.size.height,
            right: 0.0
        )

        view.layoutIfNeeded()
    }

    @objc func handleKeybolardWillHide() {
        textViewNodeLogEntry.contentInset = .zero
    }
}