Observer for keyboard (Swift)

Why Observer ?

Sometimes its useful to know when the keyboard will popup, so that we can do some extra changes in the view or call some functions with extra code.
UITextFields are enough to get the state.
but Observer to keyboard is again a plus point.

Managing the Keyboard

Although many UIKit objects display the keyboard automatically in response to user interactions, your app still has some responsibilities for configuring and managing the keyboard. The following sections describe those responsibilities.

Receiving Keyboard Notifications

When the keyboard is shown or hidden, iOS sends out the following notifications to any registered observers:

• UIKeyboardWillShowNotification
• UIKeyboardDidShowNotification
• UIKeyboardWillHideNotification
• UIKeyboardDidHideNotification

Each keyboard notification includes information about the size and position of the keyboard on the screen. You can access this information from the userInfo dictionary of each notification using the UIKeyboardFrameBeginUserInfoKey and UIKeyboardFrameEndUserInfoKey keys.

You should always use the information in these notifications as opposed to assuming the keyboard is a particular size or in a particular location. The size of the keyboard is not guaranteed to be the same from one input method to another and may also change between different releases of iOS. In addition, even for a single language and system release, the keyboard dimensions can vary depending on the orientation of your app. For example, Figure 4–3 shows the relative sizes of the URL keyboard in both the portrait and landscape modes. Using the information inside the keyboard notifications ensures that you always have the correct size and position information.

Displaying the Keyboard

When the user taps a view, the system automatically designates that view as the first responder. When this happens to a view that contains editable text, the view initiates an editing session for that text. At the beginning of that editing session, the view asks the system to display the keyboard, if it is not already visible. If the keyboard is already visible, the change in first responder causes text input from the keyboard to be redirected to the newly tapped view.

Because the keyboard is displayed automatically when a view becomes the first responder, you often do not need to do anything to display it. However, you can programmatically display the keyboard for an editable text view by calling that view’s becomeFirstRespondermethod. Calling this method makes the target view the first responder and begins the editing process just as if the user had tapped on the view.

If your app manages several text-based views on a single screen, it is a good idea to track which view is currently the first responder so that you can dismiss the keyboard later.

Dismissing the Keyboard

Although it typically displays the keyboard automatically, the system does not dismiss the keyboard automatically. Instead, it is your app’s responsibility to dismiss the keyboard at the appropriate time. Typically, you would do this in response to a user action. For example, you might dismiss the keyboard when the user taps the Return or Done button on the keyboard or taps some other button in your app’s interface. Depending on how you configured the keyboard, you might need to add some additional controls to your user interface to facilitate the keyboard’s dismissal.

To dismiss the keyboard, you call the resignFirstResponder method of the text-based view that is currently the first responder. When a text view resigns its first responder status, it ends its current editing session, notifies its delegate of that fact, and dismisses the keyboard. In other words, if you have a variable called myTextField that points to the UITextField object that is currently the first responder, dismissing the keyboard is as simple as doing the following:

Lets get started with the code…

1: Create a function and add observer to keyboard.

//Adding observer to keyboard notifications
fileprivate func observeKeyboardNotifications() {
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardShow), name: .UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(keyboardHide), name: .UIKeyboardWillHide, object: nil)
}

2: Hide keyboard and show keyboard function.

//Hide keyboard
@objc func keyboardHide() {
    //Code the lines to hide the keyboard and the extra lines you      want to execute before keyboard hides.
}
//Show keyboard
@objc func keyboardShow() {
    //Code the lines you want to execute before keyboard pops up.
}

3: Call the observer method in viewDidLoad( ).

override func viewDidLoad() {
    super.viewDidLoad()
    observeKeyboardNotifications()
}

Thank You..:-)