This Solution make sure that it hides keyboard also do nothing if it not opened. It uses extension so it can be used from any Context Owner class.

fun Context.dismissKeyboard() {
    val imm by lazy { this.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager }
    val windowHeightMethod = InputMethodManager::class.java.getMethod("getInputMethodWindowVisibleHeight")
    val height = windowHeightMethod.invoke(imm) as Int
    if (height > 0) {
        imm.toggleSoftInput(InputMethodManager.HIDE_IMPLICIT_ONLY, 0)
    }
}

By using the context of the view, we can achieve the desired outcome with the following extension methods in Kotlin:

/**
 * Get the [InputMethodManager] using some [Context].
 */
fun Context.getInputMethodManager(): InputMethodManager {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        return getSystemService(InputMethodManager::class.java)
    }

    return getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
}

/**
 * Dismiss soft input (keyboard) from the window using a [View] context.
 */
fun View.dismissKeyboard() = context
        .getInputMethodManager()
        .hideSoftInputFromWindow(
                windowToken
                , 0
        )

Once these are in place, just call:

editTextFoo.dismiss()

Kotlin:

To dismiss the keyboard, call clearFocus() on the respective element when the button is clicked.

Example:

mSearchView.clearFocus()