Clojure's Seesaw: How do I recognize that enter has been pressed

Question

http://docs.oracle.com/javase/7/docs/api/java/awt/event/KeyEvent.html#getKeyCode()

I don't know how to test if the key that was pressed was Enter. Using the following boiler plate and (alert ...). I've managed to determined that the event, e, is a KeyEvent and from its documentation I see there is a constant VK_Enter to represent Enter and three methods getKeyChar, getKeyCode and getKeyText. Using (alert e) It appears that getKeyChar returns Enter, or at least something that is represented with the Enter String, but (= (.getKeyChar e) "Enter") returns false. How can I detect that Enter was pressed?

(-> (frame :title "Zangalon" :content
           (text :text "Input Goes here"
                 :listen [:key-typed (fn [e] ..)]))
    pack!
    show!)

VK_Enter

Answer 1

A working example:

(ns user
  (:require [seesaw.core :as ui]))

(defn keypress [e]
  (let [k (.getKeyChar e)]
    (prn k (type k))
    (if (= k \newline)
      (prn "ENTER!")
      (prn "some other key"))))

(defn run []
  (-> (ui/frame :title "Zangalon" :content
                (ui/text :text "Input Goes here"
                         :listen [:key-typed keypress]))
      ui/pack!
      ui/show!))

and the output:

\q java.lang.Character
"some other key"
\w java.lang.Character
"some other key"
\e java.lang.Character
"some other key"
\newline java.lang.Character
"ENTER!"
\newline java.lang.Character
"ENTER!"

Event itself is:

#<KeyEvent java.awt.event.KeyEvent[KEY_TYPED,keyCode=0,keyText=Unknown keyCode: 0x0,keyChar=Enter,keyLocation=KEY_LOCATION_UNKNOWN,rawCode=0,primaryLevelUnicode=10,scancode=0,extendedKeyCode=0x0] ...>

As you can see keyCode is 0 so .getKeyCode will not work.

java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)

Answer 2

Try this:

(fn [e]
  (if (= java.awt.event.KeyEvent/VK_ENTER (.getKeyCode e))
    ...)

---

EDIT: (based on conversation with @edbond in comments)

TLDR: use getKeyChar for :key-typed events and getKeyCode for :key-released or :key-pressed ; depending on your use case, any of the three types of events may be suitable.

Quoting KeyEvent's documentation:

"Key typed" events are higher-level and generally do not depend on the platform or keyboard layout. They are generated when a Unicode character is entered, and are the preferred way to find out about character input. In the simplest case, a key typed event is produced by a single key press (e.g., 'a'). Often, however, characters are produced by series of key presses (e.g., 'shift' + 'a'), and the mapping from key pressed events to key typed events may be many-to-one or many-to-many. Key releases are not usually necessary to generate a key typed event, but there are some cases where the key typed event is not generated until a key is released (e.g., entering ASCII sequences via the Alt-Numpad method in Windows). No key typed events are generated for keys that don't generate Unicode characters (e.g., action keys, modifier keys, etc.).

The getKeyChar method always returns a valid Unicode character or CHAR_UNDEFINED. Character input is reported by KEY_TYPED events: KEY_PRESSED and KEY_RELEASED events are not necessarily associated with character input. Therefore, the result of the getKeyChar method is guaranteed to be meaningful only for KEY_TYPED events.

For key pressed and key released events, the getKeyCode method returns the event's keyCode. For key typed events, the getKeyCode method always returns VK_UNDEFINED. The getExtendedKeyCode method may also be used with many international keyboard layouts.

"Key pressed" and "key released" events are lower-level and depend on the platform and keyboard layout. They are generated whenever a key is pressed or released, and are the only way to find out about keys that don't generate character input (e.g., action keys, modifier keys, etc.). The key being pressed or released is indicated by the getKeyCode and getExtendedKeyCode methods, which return a virtual key code.

Answer 3

check if it is = to the character \newline

user> (java.net.URLDecoder/decode "%00")
true

so

...
(fn [e] (= \newline (.getKeyChar e))