Differentiating a text code key from a control code in an Android KeyEvent

Question

There are 284 KeyEvent key codes . Some of them represent Unicode characters (for example, KEYCODE_A and KEYCODE_1 ), while others represent control characters (for example, KEYCODE_DEL ).

I am creating a custom view that handles keyboard input . It receives most of its input from the input connection, but sometimes the keyboard sends key codes (normal, associated with hard keyboard input). I need to handle this too. Should I exhaustively process each key code control and then convert the rest to text (using (char) event.getUnicodeChar() ) or is there a built-in way to differentiate text codes from control codes?

Answer 1

Documentation KeyEvent.getUnicodeChar() reports

Returns 0 if the key is not used to enter Unicode characters.

Thus, it is easy to distinguish text codes from control codes, for example:

 if (keyEvent.getUnicodeChar() != 0) { // unicode text char unicodeChar = (char) keyEvent.getUnicodeChar(); } else { // control char } 

Here is a list that helped me reach this agreement:

 // keyCode, Unicode, char, keyCode name 0 0    KEYCODE_UNKNOWN 1 0    KEYCODE_SOFT_LEFT 2 0    KEYCODE_SOFT_RIGHT 3 0    KEYCODE_HOME 4 0    KEYCODE_BACK 5 0    KEYCODE_CALL 6 0    KEYCODE_ENDCALL 7 48 0 KEYCODE_0 8 49 1 KEYCODE_1 9 50 2 KEYCODE_2 10 51 3 KEYCODE_3 11 52 4 KEYCODE_4 12 53 5 KEYCODE_5 13 54 6 KEYCODE_6 14 55 7 KEYCODE_7 15 56 8 KEYCODE_8 16 57 9 KEYCODE_9 17 42 * KEYCODE_STAR 18 35 # KEYCODE_POUND 19 0    KEYCODE_DPAD_UP 20 0    KEYCODE_DPAD_DOWN 21 0    KEYCODE_DPAD_LEFT 22 0    KEYCODE_DPAD_RIGHT 23 0    KEYCODE_DPAD_CENTER 24 0    KEYCODE_VOLUME_UP 25 0    KEYCODE_VOLUME_DOWN 26 0    KEYCODE_POWER 27 0    KEYCODE_CAMERA 28 0    KEYCODE_CLEAR 29 97 a KEYCODE_A 30 98 b KEYCODE_B 31 99 c KEYCODE_C 32 100 d KEYCODE_D 33 101 e KEYCODE_E 34 102 f KEYCODE_F 35 103 g KEYCODE_G 36 104 h KEYCODE_H 37 105 i KEYCODE_I 38 106 j KEYCODE_J 39 107 k KEYCODE_K 40 108 l KEYCODE_L 41 109 m KEYCODE_M 42 110 n KEYCODE_N 43 111 o KEYCODE_O 44 112 p KEYCODE_P 45 113 q KEYCODE_Q 46 114 r KEYCODE_R 47 115 s KEYCODE_S 48 116 t KEYCODE_T 49 117 u KEYCODE_U 50 118 v KEYCODE_V 51 119 w KEYCODE_W 52 120 x KEYCODE_X 53 121 y KEYCODE_Y 54 122 z KEYCODE_Z 55 44 , KEYCODE_COMMA 56 46 . KEYCODE_PERIOD 57 0    KEYCODE_ALT_LEFT 58 0    KEYCODE_ALT_RIGHT 59 0    KEYCODE_SHIFT_LEFT 60 0    KEYCODE_SHIFT_RIGHT 61 9 KEYCODE_TAB 62 32 KEYCODE_SPACE 63 0    KEYCODE_SYM 64 0    KEYCODE_EXPLORER 65 0    KEYCODE_ENVELOPE 66 10 KEYCODE_ENTER 67 0    KEYCODE_DEL 68 96 ` KEYCODE_GRAVE 69 45 - KEYCODE_MINUS 70 61 = KEYCODE_EQUALS 71 91 [ KEYCODE_LEFT_BRACKET 72 93 ] KEYCODE_RIGHT_BRACKET 73 92 \ KEYCODE_BACKSLASH 74 59 ; KEYCODE_SEMICOLON 75 39 ' KEYCODE_APOSTROPHE 76 47 / KEYCODE_SLASH 77 64 @ KEYCODE_AT 78 0    KEYCODE_NUM 79 0    KEYCODE_HEADSETHOOK 80 0    KEYCODE_FOCUS 81 43 + KEYCODE_PLUS 82 0    KEYCODE_MENU 83 0    KEYCODE_NOTIFICATION 84 0    KEYCODE_SEARCH 85 0    KEYCODE_MEDIA_PLAY_PAUSE 86 0    KEYCODE_MEDIA_STOP 87 0    KEYCODE_MEDIA_NEXT 88 0    KEYCODE_MEDIA_PREVIOUS 89 0    KEYCODE_MEDIA_REWIND 90 0    KEYCODE_MEDIA_FAST_FORWARD 91 0    KEYCODE_MUTE 92 0    KEYCODE_PAGE_UP 93 0    KEYCODE_PAGE_DOWN 94 0    KEYCODE_PICTSYMBOLS 95 0    KEYCODE_SWITCH_CHARSET 96 0    KEYCODE_BUTTON_A 97 0    KEYCODE_BUTTON_B 98 0    KEYCODE_BUTTON_C 99 0    KEYCODE_BUTTON_X 100 0    KEYCODE_BUTTON_Y 101 0    KEYCODE_BUTTON_Z 102 0    KEYCODE_BUTTON_L1 103 0    KEYCODE_BUTTON_R1 104 0    KEYCODE_BUTTON_L2 105 0    KEYCODE_BUTTON_R2 106 0    KEYCODE_BUTTON_THUMBL 107 0    KEYCODE_BUTTON_THUMBR 108 0    KEYCODE_BUTTON_START 109 0    KEYCODE_BUTTON_SELECT 110 0    KEYCODE_BUTTON_MODE 111 0    KEYCODE_ESCAPE 112 0    KEYCODE_FORWARD_DEL 113 0    KEYCODE_CTRL_LEFT 114 0    KEYCODE_CTRL_RIGHT 115 0    KEYCODE_CAPS_LOCK 116 0    KEYCODE_SCROLL_LOCK 117 0    KEYCODE_META_LEFT 118 0    KEYCODE_META_RIGHT 119 0    KEYCODE_FUNCTION 120 0    KEYCODE_SYSRQ 121 0    KEYCODE_BREAK 122 0    KEYCODE_MOVE_HOME 123 0    KEYCODE_MOVE_END 124 0    KEYCODE_INSERT 125 0    KEYCODE_FORWARD 126 0    KEYCODE_MEDIA_PLAY 127 0    KEYCODE_MEDIA_PAUSE 128 0    KEYCODE_MEDIA_CLOSE 129 0    KEYCODE_MEDIA_EJECT 130 0    KEYCODE_MEDIA_RECORD 131 0    KEYCODE_F1 132 0    KEYCODE_F2 133 0    KEYCODE_F3 134 0    KEYCODE_F4 135 0    KEYCODE_F5 136 0    KEYCODE_F6 137 0    KEYCODE_F7 138 0    KEYCODE_F8 139 0    KEYCODE_F9 140 0    KEYCODE_F10 141 0    KEYCODE_F11 142 0    KEYCODE_F12 143 0    KEYCODE_NUM_LOCK 144 0    KEYCODE_NUMPAD_0 145 0    KEYCODE_NUMPAD_1 146 0    KEYCODE_NUMPAD_2 147 0    KEYCODE_NUMPAD_3 148 0    KEYCODE_NUMPAD_4 149 0    KEYCODE_NUMPAD_5 150 0    KEYCODE_NUMPAD_6 151 0    KEYCODE_NUMPAD_7 152 0    KEYCODE_NUMPAD_8 153 0    KEYCODE_NUMPAD_9 154 47 / KEYCODE_NUMPAD_DIVIDE 155 42 * KEYCODE_NUMPAD_MULTIPLY 156 45 - KEYCODE_NUMPAD_SUBTRACT 157 43 + KEYCODE_NUMPAD_ADD 158 0    KEYCODE_NUMPAD_DOT 159 44 , KEYCODE_NUMPAD_COMMA 160 10 KEYCODE_NUMPAD_ENTER 161 61 = KEYCODE_NUMPAD_EQUALS 162 40 ( KEYCODE_NUMPAD_LEFT_PAREN 163 41 ) KEYCODE_NUMPAD_RIGHT_PAREN 164 0    KEYCODE_VOLUME_MUTE 165 0    KEYCODE_INFO 166 0    KEYCODE_CHANNEL_UP 167 0    KEYCODE_CHANNEL_DOWN 168 0    KEYCODE_ZOOM_IN 169 0    KEYCODE_ZOOM_OUT 170 0    KEYCODE_TV 171 0    KEYCODE_WINDOW 172 0    KEYCODE_GUIDE 173 0    KEYCODE_DVR 174 0    KEYCODE_BOOKMARK 175 0    KEYCODE_CAPTIONS 176 0    KEYCODE_SETTINGS 177 0    KEYCODE_TV_POWER 178 0    KEYCODE_TV_INPUT 179 0    KEYCODE_STB_POWER 180 0    KEYCODE_STB_INPUT 181 0    KEYCODE_AVR_POWER 182 0    KEYCODE_AVR_INPUT 183 0    KEYCODE_PROG_RED 184 0    KEYCODE_PROG_GREEN 185 0    KEYCODE_PROG_YELLOW 186 0    KEYCODE_PROG_BLUE 187 0    KEYCODE_APP_SWITCH 188 0    KEYCODE_BUTTON_1 189 0    KEYCODE_BUTTON_2 190 0    KEYCODE_BUTTON_3 191 0    KEYCODE_BUTTON_4 192 0    KEYCODE_BUTTON_5 193 0    KEYCODE_BUTTON_6 194 0    KEYCODE_BUTTON_7 195 0    KEYCODE_BUTTON_8 196 0    KEYCODE_BUTTON_9 197 0    KEYCODE_BUTTON_10 198 0    KEYCODE_BUTTON_11 199 0    KEYCODE_BUTTON_12 200 0    KEYCODE_BUTTON_13 201 0    KEYCODE_BUTTON_14 202 0    KEYCODE_BUTTON_15 203 0    KEYCODE_BUTTON_16 204 0    KEYCODE_LANGUAGE_SWITCH 205 0    KEYCODE_MANNER_MODE 206 0    KEYCODE_3D_MODE 207 0    KEYCODE_CONTACTS 208 0    KEYCODE_CALENDAR 209 0    KEYCODE_MUSIC 210 0    KEYCODE_CALCULATOR 211 0    KEYCODE_ZENKAKU_HANKAKU 212 0    KEYCODE_EISU 213 0    KEYCODE_MUHENKAN 214 0    KEYCODE_HENKAN 215 0    KEYCODE_KATAKANA_HIRAGANA 216 0    KEYCODE_YEN 217 0    KEYCODE_RO 218 0    KEYCODE_KANA 219 0    KEYCODE_ASSIST 220 0    KEYCODE_BRIGHTNESS_DOWN 221 0    KEYCODE_BRIGHTNESS_UP 222 0    KEYCODE_MEDIA_AUDIO_TRACK 223 0    KEYCODE_SLEEP 224 0    KEYCODE_WAKEUP 225 0    KEYCODE_PAIRING 226 0    KEYCODE_MEDIA_TOP_MENU 227 0    KEYCODE_11 228 0    KEYCODE_12 229 0    KEYCODE_LAST_CHANNEL 230 0    KEYCODE_TV_DATA_SERVICE 231 0    KEYCODE_VOICE_ASSIST 232 0    KEYCODE_TV_RADIO_SERVICE 233 0    KEYCODE_TV_TELETEXT 234 0    KEYCODE_TV_NUMBER_ENTRY 235 0    KEYCODE_TV_TERRESTRIAL_ANALOG 236 0    KEYCODE_TV_TERRESTRIAL_DIGITAL 237 0    KEYCODE_TV_SATELLITE 238 0    KEYCODE_TV_SATELLITE_BS 239 0    KEYCODE_TV_SATELLITE_CS 240 0    KEYCODE_TV_SATELLITE_SERVICE 241 0    KEYCODE_TV_NETWORK 242 0    KEYCODE_TV_ANTENNA_CABLE 243 0    KEYCODE_TV_INPUT_HDMI_1 244 0    KEYCODE_TV_INPUT_HDMI_2 245 0    KEYCODE_TV_INPUT_HDMI_3 246 0    KEYCODE_TV_INPUT_HDMI_4 247 0    KEYCODE_TV_INPUT_COMPOSITE_1 248 0    KEYCODE_TV_INPUT_COMPOSITE_2 249 0    KEYCODE_TV_INPUT_COMPONENT_1 250 0    KEYCODE_TV_INPUT_COMPONENT_2 251 0    KEYCODE_TV_INPUT_VGA_1 252 0    KEYCODE_TV_AUDIO_DESCRIPTION 253 0    KEYCODE_TV_AUDIO_DESCRIPTION_MIX_UP 254 0    KEYCODE_TV_AUDIO_DESCRIPTION_MIX_DOWN 255 0    KEYCODE_TV_ZOOM_MODE 256 0    KEYCODE_TV_CONTENTS_MENU 257 0    KEYCODE_TV_MEDIA_CONTEXT_MENU 258 0    KEYCODE_TV_TIMER_PROGRAMMING 259 0    KEYCODE_HELP 260 0    KEYCODE_NAVIGATE_PREVIOUS 261 0    KEYCODE_NAVIGATE_NEXT 262 0    KEYCODE_NAVIGATE_IN 263 0    KEYCODE_NAVIGATE_OUT 264 0    KEYCODE_STEM_PRIMARY 265 0    KEYCODE_STEM_1 266 0    KEYCODE_STEM_2 267 0    KEYCODE_STEM_3 268 0    KEYCODE_DPAD_UP_LEFT 269 0    KEYCODE_DPAD_DOWN_LEFT 270 0    KEYCODE_DPAD_UP_RIGHT 271 0    KEYCODE_DPAD_DOWN_RIGHT 272 0    KEYCODE_MEDIA_SKIP_FORWARD 273 0    KEYCODE_MEDIA_SKIP_BACKWARD 274 0    KEYCODE_MEDIA_STEP_FORWARD 275 0    KEYCODE_MEDIA_STEP_BACKWARD 276 0    KEYCODE_SOFT_SLEEP 277 0    KEYCODE_CUT 278 0    KEYCODE_COPY 279 0    KEYCODE_PASTE 280 0    KEYCODE_SYSTEM_NAVIGATION_UP 281 0    KEYCODE_SYSTEM_NAVIGATION_DOWN 282 0    KEYCODE_SYSTEM_NAVIGATION_LEFT 283 0    KEYCODE_SYSTEM_NAVIGATION_RIGHT 

Dead keys

Please note that you may also need to accept dead keys . docs say

The system recognizes the following Unicode characters as a combination of diacritical dead key characters.

• '\u0300' : strong accent.
• '\u0301' : A sharp accent.
• '\u0302' : Circumflex accent.
• '\u0303' : Emphasis on tilde.
• '\u0308' : Umlaut accent.

When a dead key is typed, followed by another character, a dead key and the following characters are composed. For example, when the user type of dead key is a serious accent followed by the letter "a", the result is 'a'.

To get the dead key, a combination of KeyEvent.getDeadChar() , COMBINING_ACCENT and COMBINING_ACCENT_MASK . The following method is used in many open source projects to send InputConnection events to InputConnection .

 /** * This translates incoming hard key events in to edit operations on an * InputConnection. It is only needed when using the * PROCESS_HARD_KEYS option. */ private boolean translateKeyDown(int keyCode, KeyEvent event) { mMetaState = MetaKeyKeyListener.handleKeyDown(mMetaState, keyCode, event); int c = event.getUnicodeChar(MetaKeyKeyListener.getMetaState(mMetaState)); mMetaState = MetaKeyKeyListener.adjustMetaAfterKeypress(mMetaState); InputConnection ic = getCurrentInputConnection(); if (c == 0 || ic == null) { return false; } boolean dead = false; if ((c & KeyCharacterMap.COMBINING_ACCENT) != 0) { dead = true; c = c & KeyCharacterMap.COMBINING_ACCENT_MASK; } if (mComposing.length() > 0) { char accent = mComposing.charAt(mComposing.length() -1 ); int composed = KeyEvent.getDeadChar(accent, c); if (composed != 0) { c = composed; mComposing.setLength(mComposing.length()-1); } } onKey(c, null); return true; } 

Another way?

@pskink mentions TextKeyListener , BaseKeyListener and KeyListener . This may be the best way. However, I could not find an adequate explanation and examples of how to use them.