Android HID device (keyboard, remote control, etc.) function implementation process and key-value mapping relationship

　HID (Human Interface Device) is a commonly used device type in USB devices . It is a USB device that directly interacts with humans, such as keyboard, remote control, mouse, and joystick. Among USB devices, HID devices cost less.

    The previous article  Android Keyboard (Remote Control) Key Value Definitions  compiled the definitions of various function keys in Android. So what is the process from keyboard keys to Android device control taking effect?

Keyboard operation implementation process on Android devices:

1. EventHub The raw events are read from  evdev the driver and the Linux key codes (sometimes called scan codes) are mapped into Android key codes using the keyboard's key layout mapping.

2. InputReader The original event will be consumed and the meta key state will be updated. For example, if you press or release the left Shift key, the reader sets or resets the  META_SHIFT_LEFT_ON bits  accordingly META_SHIFT_ON .

3. InputReaderInputDispatcher Notifications related to key events  will be sent to  .

4. InputDispatcherWindowManagerPolicy.interceptKeyBeforeQueueing Ask  WindowManagerPolicy how to handle key events  by calling  . This method (responsible for waking the device when certain keys are pressed) is part of the critical path. In effect, EventHub the wake lock is held on this critical path, ensuring that it runs to completion.

5. If it is currently in use  InputFilter,  InputDispatcher it will be given the opportunity to consume or convert keystrokes. InputFilter Can be used to implement low-level, system-wide accessibility policies.

6. InputDispatcher Keystrokes can be queued for processing on the dispatch thread.

7. When  InputDispatcher a key is removed from the queue, it gives   another chance to intercept the key event WindowManagerPolicy.interceptKeyBeforeDispatching by  calling WindowManagerPolicyThis method can be used to handle system shortcuts and other features.

8. Then, InputDispatcher the key event target (the focused window) is identified and waits for the key event target to be ready. Next, InputDispatcher the key event is sent to the app.

9. Within the app, key events are passed down the view hierarchy to the focused view for IME key preassignment.

10. If the key event is not processed in the IME key pre-assignment phase and an IME is in use, the key event will be sent to the IME.

11. If the key event is not consumed by the IME, the key event is passed down the view hierarchy to the focused view, allowing standard key assignment.

12. The application in turn reports back to  InputDispatcher the application whether the key event was used. If the event is not used, InputDispatcher it is called  WindowManagerPolicy.dispatchUnhandledKey to apply "fallback" behavior. Depending on the rollback operation, the key event distribution cycle can be restarted with a different key code. For example, if the app doesn't handle it  KEYCODE_ESCAPE, the system might instead treat the key event as  KEYCODE_BACK a reassignment.

HID usage is represented by two code values, which represent the key type and key value respectively. For example, 0x07 represents the key type as a function key , and 0x0001 represents the key value. Take USB remote control as an example :

Common key categories are as follows:

1. Control Key:

   • Code value 0x01: Ctrl key

2. Modifier Key:

   • Code value 0x02: Shift key
   • Code value 0x03: Alt key
   • Code value 0x04: GUI key (for example, Windows key or Command key)
   • Code value 0x05: Caps Lock key
   • Code value 0x06: Num Lock key

3. Navigation Key:

   • Code value 0x08: up arrow
   • Code value 0x09: down arrow
   • Code value 0x0A: right arrow
   • Code value 0x0B: left arrow
   • Code value 0x0C: Home key
   • Code value 0x0D: end key
   • Code value 0x0E: key on page
   • Code value 0x0F: page down button

4. Function Key:

   • Code value 0x07: usually represents a function key, but there can also be code values ​​for other custom function keys.

HID usage, Linux keycodes, and Android keycodes

The LKC column specifies Linux key codes in hexadecimal format.

The AKC column specifies Android key codes in hexadecimal format.

HID usage	HID usage name	LKC	Linux key code name	Version	AKC	Android key code name	Remark
0x07 0x0001	Keyboard bugs, anti-ghosting
0x07 0x0002	Keyboard POST failed
0x07 0x0003	keyboard error undefined
0x07 0x0004	Keyboard a and A keys	0x001e	KEY_A	1.6	0x001d	KEYCODE_A	1
0x07 0x0005	Keyboard b and B keys	0x0030	KEY_B	1.6	0x001e	KEYCODE_B	1
0x07 0x0006	Keyboard c and C keys	0x002e	KEY_C	1.6	0x001f	KEYCODE_C	1
0x07 0x0007	Keyboard d and D keys	0x0020	KEY_D	1.6	0x0020	KEYCODE_D	1
0x07 0x0008	Keyboard e and E keys	0x0012	KEY_E	1.6	0x0021	KEYCODE_E	1
0x07 0x0009	Keyboard f and F keys	0x0021	KEY_F	1.6	0x0022	KEYCODE_F	1
0x07 0x000a	Keyboard g and G keys	0x0022	KEY_G	1.6	0x0023	KEYCODE_G	1
0x07 0x000b	Keyboard h and H keys	0x0023	KEY_H	1.6	0x0024	KEYCODE_H	1
0x07 0x000c	Keyboard i and I keys	0x0017	KEY_I	1.6	0x0025	KEYCODE_I	1
0x07 0x000d	Keyboard j and J keys	0x0024	KEY_J	1.6	0x0026	KEYCODE_J	1
0x07 0x000e	Keyboard k and K keys	0x0025	KEY_K	1.6	0x0027	KEYCODE_K	1
0x07 0x000f	Keyboard l and L keys	0x0026	KEY_L	1.6	0x0028	KEYCODE_L	1
0x07 0x0010	Keyboard m and M keys	0x0032	KEY_M	1.6	0x0029	KEYCODE_M	1
0x07 0x0011	Keyboard n and N keys	0x0031	KEY_N	1.6	0x002a	KEYCODE_N	1
0x07 0x0012	Keyboard o and O keys	0x0018	KEY_O	1.6	0x002b	KEYCODE_O	1
0x07 0x0013	Keyboard p and P keys	0x0019	KEY_P	1.6	0x002c	KEYCODE_P	1
0x07 0x0014	Keyboard q and Q keys	0x0010	KEY_Q	1.6	0x002d	KEYCODE_Q	1
0x07 0x0015	Keyboard r and R keys	0x0013	KEY_R	1.6	0x002e	KEYCODE_R	1
0x07 0x0016	Keyboard s and S keys	0x001f	KEY_S	1.6	0x002f	KEYCODE_S	1
0x07 0x0017	Keyboard t and T keys	0x0014	KEY_T	1.6	0x0030	KEYCODE_T	1
0x07 0x0018	Keyboard u and U keys	0x0016	KEY_U	1.6	0x0031	KEYCODE_U	1
0x07 0x0019	Keyboard v and V keys	0x002f	KEY_V	1.6	0x0032	KEYCODE_V	1
0x07 0x001a	Keyboard w and W keys	0x0011	KEY_W	1.6	0x0033	KEYCODE_W	1
0x07 0x001b	Keyboard x and X keys	0x002d	KEY_X	1.6	0x0034	KEYCODE_X	1
0x07 0x001c	键盘 y 和 Y 键	0x0015	KEY_Y	1.6	0x0035	KEYCODE_Y	1
0x07 0x001d	键盘 z 和 Z 键	0x002c	KEY_Z	1.6	0x0036	KEYCODE_Z	1
0x07 0x001e	键盘 1 和 ! 键	0x0002	KEY_1	1.6	0x0008	KEYCODE_1	1
0x07 0x001f	键盘 2 和 @ 键	0x0003	KEY_2	1.6	0x0009	KEYCODE_2	1
0x07 0x0020	键盘 3 和 # 键	0x0004	KEY_3	1.6	0x000a	KEYCODE_3	1
0x07 0x0021	键盘 4 和 $ 键	0x0005	KEY_4	1.6	0x000b	KEYCODE_4	1
0x07 0x0022	键盘 5 和 % 键	0x0006	KEY_5	1.6	0x000c	KEYCODE_5	1
0x07 0x0023	键盘 6 和 ^ 键	0x0007	KEY_6	1.6	0x000d	KEYCODE_6	1
0x07 0x0024	键盘 7 和 & 键	0x0008	KEY_7	1.6	0x000e	KEYCODE_7	1
0x07 0x0025	键盘 8 和 * 键	0x0009	KEY_8	1.6	0x000f	KEYCODE_8	1
0x07 0x0026	键盘 9 和 ( 键	0x000a	KEY_9	1.6	0x0010	KEYCODE_9	1
0x07 0x0027	键盘 0 和 ) 键	0x000b	KEY_0	1.6	0x0007	KEYCODE_0	1
0x07 0x0028	键盘返回 (Enter) 键	0x001c	KEY_ENTER	1.6	0x0042	KEYCODE_ENTER	1
0x07 0x0029	键盘 Esc 键	0x0001	KEY_ESC	3.0	0x006f	KEYCODE_ESCAPE
""	""	""	""	2.3	0x0004	KEYCODE_BACK
0x07 0x002a	键盘删除 (Backspace) 键	0x000e	KEY_BACKSPACE	1.6	0x0043	KEYCODE_DEL
0x07 0x002b	键盘 Tab 键	0x000f	KEY_TAB	1.6	0x003d	KEYCODE_TAB
0x07 0x002c	键盘空格键	0x0039	KEY_SPACE	1.6	0x003e	KEYCODE_SPACE
0x07 0x002d	键盘 - 和 _ 键	0x000c	KEY_MINUS	1.6	0x0045	KEYCODE_MINUS	1
0x07 0x002e	键盘 = 和 + 键	0x000d	KEY_EQUAL	1.6	0x0046	KEYCODE_EQUALS	1
0x07 0x002f	键盘 [ 和 { 键	0x001a	KEY_LEFTBRACE	1.6	0x0047	KEYCODE_LEFT_BRACKET	1
0x07 0x0030	键盘 ] 和 } 键	0x001b	KEY_RIGHTBRACE	1.6	0x0048	KEYCODE_RIGHT_BRACKET	1
0x07 0x0031	键盘 \ 和 | 键	0x002b	KEY_BACKSLASH	1.6	0x0049	KEYCODE_BACKSLASH	1
0x07 0x0032	键盘非美式 # 和 ~ 键	0x002b	KEY_BACKSLASH	1.6	0x0049	KEYCODE_BACKSLASH	1
0x07 0x0033	键盘 ; 和 : 键	0x0027	KEY_SEMICOLON	1.6	0x004a	KEYCODE_SEMICOLON	1
0x07 0x0034	键盘 ' 和 " 键	0x0028	KEY_APOSTROPHE	1.6	0x004b	KEYCODE_APOSTROPHE	1
0x07 0x0035	键盘 ` 和 ~ 键	0x0029	KEY_GRAVE	3.0	0x0044	KEYCODE_GRAVE	1
0x07 0x0036	键盘 , 和 < 键	0x0033	KEY_COMMA	1.6	0x0037	KEYCODE_COMMA	1
0x07 0x0037	键盘 . 和 > 键	0x0034	KEY_DOT	1.6	0x0038	KEYCODE_PERIOD	1
0x07 0x0038	键盘 / 和 ? 键	0x0035	KEY_SLASH	1.6	0x004c	KEYCODE_SLASH	1
0x07 0x0039	键盘 Caps Lock 键	0x003a	KEY_CAPSLOCK	3.0	0x0073	KEYCODE_CAPS_LOCK
0x07 0x003a	键盘 F1 键	0x003b	KEY_F1	3.0	0x0083	KEYCODE_F1
""	""	""	""	1.6	0x0052	KEYCODE_MENU
0x07 0x003b	键盘 F2 键	0x003c	KEY_F2	3.0	0x0084	KEYCODE_F2
""	""	""	""	1.6	0x0002	KEYCODE_SOFT_RIGHT
0x07 0x003c	键盘 F3 键	0x003d	KEY_F3	3.0	0x0085	KEYCODE_F3
""	""	""	""	1.6	0x0005	KEYCODE_CALL
0x07 0x003d	键盘 F4 键	0x003e	KEY_F4	3.0	0x0086	KEYCODE_F4
""	""	""	""	1.6	0x0006	KEYCODE_ENDCALL
0x07 0x003e	键盘 F5 键	0x003f	KEY_F5	3.0	0x0087	KEYCODE_F5
0x07 0x003f	键盘 F6 键	0x0040	KEY_F6	3.0	0x0088	KEYCODE_F6
0x07 0x0040	键盘 F7 键	0x0041	KEY_F7	3.0	0x0089	KEYCODE_F7
0x07 0x0041	键盘 F8 键	0x0042	KEY_F8	3.0	0x008a	KEYCODE_F8
0x07 0x0042	键盘 F9 键	0x0043	KEY_F9	3.0	0x008b	KEYCODE_F9
0x07 0x0043	键盘 F10 键	0x0044	KEY_F10	3.0	0x008c	KEYCODE_F10
""	""	""	""	2.3	0x0052	KEYCODE_MENU
0x07 0x0044	键盘 F11 键	0x0057	KEY_F11	3.0	0x008d	KEYCODE_F11
0x07 0x0045	键盘 F12 键	0x0058	KEY_F12	3.0	0x008e	KEYCODE_F12
0x07 0x0046	键盘 Print Screen 键	0x0063	KEY_SYSRQ	3.0	0x0078	KEYCODE_SYSRQ
0x07 0x0047	键盘 Scroll Lock 键	0x0046	KEY_SCROLLLOCK	3.0	0x0074	KEYCODE_SCROLL_LOCK
0x07 0x0048	键盘 Pause 键	0x0077	KEY_PAUSE	3.0	0x0079	KEYCODE_BREAK
0x07 0x0049	键盘 Insert 键	0x006e	KEY_INSERT	3.0	0x007c	KEYCODE_INSERT
0x07 0x004a	键盘 Home 键	0x0066	KEY_HOME	3.0	0x007a	KEYCODE_MOVE_HOME
""	""	""	""	1.6	0x0003	KEYCODE_HOME
0x07 0x004b	键盘 Page Up 键	0x0068	KEY_PAGEUP	3.0	0x005c	KEYCODE_PAGE_UP
0x07 0x004c	键盘 Delete Forward 键	0x006f	KEY_DELETE	3.0	0x0070	KEYCODE_FORWARD_DEL
0x07 0x004d	键盘 End 键	0x006b	KEY_END	3.0	0x007b	KEYCODE_MOVE_END
""	""	""	""	1.6	0x0006	KEYCODE_ENDCALL
0x07 0x004e	键盘 Page Down 键	0x006d	KEY_PAGEDOWN	3.0	0x005d	KEYCODE_PAGE_DOWN
0x07 0x004f	键盘向右箭头键	0x006a	KEY_RIGHT	1.6	0x0016	KEYCODE_DPAD_RIGHT
0x07 0x0050	键盘向左箭头键	0x0069	KEY_LEFT	1.6	0x0015	KEYCODE_DPAD_LEFT
0x07 0x0051	键盘向下箭头键	0x006c	KEY_DOWN	1.6	0x0014	KEYCODE_DPAD_DOWN
0x07 0x0052	键盘向上箭头键	0x0067	KEY_UP	1.6	0x0013	KEYCODE_DPAD_UP
0x07 0x0053	键盘 Num Lock 和 Clear 键	0x0045	KEY_NUMLOCK	3.0	0x008f	KEYCODE_NUM_LOCK
0x07 0x0054	小键盘 / 键	0x0062	KEY_KPSLASH	3.0	0x009a	KEYCODE_NUMPAD_DIVIDE
0x07 0x0055	小键盘 * 键	0x0037	KEY_KPASTERISK	3.0	0x009b	KEYCODE_NUMPAD_MULTIPLY
0x07 0x0056	小键盘 - 键	0x004a	KEY_KPMINUS	3.0	0x009c	KEYCODE_NUMPAD_SUBTRACT
0x07 0x0057	小键盘 + 键	0x004e	KEY_KPPLUS	3.0	0x009d	KEYCODE_NUMPAD_ADD
0x07 0x0058	小键盘 Enter 键	0x0060	KEY_KPENTER	3.0	0x00a0	KEYCODE_NUMPAD_ENTER
0x07 0x0059	小键盘 1 和 End 键	0x004f	KEY_KP1	3.0	0x0091	KEYCODE_NUMPAD_1
0x07 0x005a	小键盘 2 和向下箭头键	0x0050	KEY_KP2	3.0	0x0092	KEYCODE_NUMPAD_2
0x07 0x005b	小键盘 3 和 PageDn 键	0x0051	KEY_KP3	3.0	0x0093	KEYCODE_NUMPAD_3
0x07 0x005c	小键盘 4 和向左箭头键	0x004b	KEY_KP4	3.0	0x0094	KEYCODE_NUMPAD_4
0x07 0x005d	小键盘 5 键	0x004c	KEY_KP5	3.0	0x0095	KEYCODE_NUMPAD_5
0x07 0x005e	小键盘 6 和向右箭头键	0x004d	KEY_KP6	3.0	0x0096	KEYCODE_NUMPAD_6
0x07 0x005f	小键盘 7 和 Home 键	0x0047	KEY_KP7	3.0	0x0097	KEYCODE_NUMPAD_7
0x07 0x0060	小键盘 8 和向上箭头键	0x0048	KEY_KP8	3.0	0x0098	KEYCODE_NUMPAD_8
0x07 0x0061	小键盘 9 和 Page Up 键	0x0049	KEY_KP9	3.0	0x0099	KEYCODE_NUMPAD_9
0x07 0x0062	小键盘 0 和 Insert 键	0x0052	KEY_KP0	3.0	0x0090	KEYCODE_NUMPAD_0
0x07 0x0063	小键盘 . 键（删除键）	0x0053	KEY_KPDOT	3.0	0x009e	KEYCODE_NUMPAD_DOT
0x07 0x0064	键盘 Non-US \ 和 | 键	0x0056	KEY_102ND	4.0	0x0049	KEYCODE_BACKSLASH	1
0x07 0x0065	键盘应用键	0x007f	KEY_COMPOSE	3.0	0x0052	KEYCODE_MENU
""	""	""	""	1.6	0x0054	KEYCODE_SEARCH
0x07 0x0066	键盘 Power 键	0x0074	KEY_POWER	1.6	0x001a	KEYCODE_POWER
0x07 0x0067	小键盘 = 键	0x0075	KEY_KPEQUAL	3.0	0x00a1	KEYCODE_NUMPAD_EQUALS
0x07 0x0068	键盘 F13 键	0x00b7	KEY_F13
0x07 0x0069	键盘 F14 键	0x00b8	KEY_F14
0x07 0x006a	键盘 F15 键	0x00b9	KEY_F15
0x07 0x006b	键盘 F16 键	0x00ba	KEY_F16
0x07 0x006c	键盘 F17 键	0x00bb	KEY_F17
0x07 0x006d	键盘 F18 键	0x00bc	KEY_F18
0x07 0x006e	键盘 F19 键	0x00bd	KEY_F19
0x07 0x006f	键盘 F20 键	0x00be	KEY_F20
0x07 0x0070	键盘 F21 键	0x00bf	KEY_F21
0x07 0x0071	键盘 F22 键	0x00c0	KEY_F22
0x07 0x0072	键盘 F23 键	0x00c1	KEY_F23
0x07 0x0073	键盘 F24 键	0x00c2	KEY_F24
0x07 0x0074	键盘 Execute 键	0x0086	KEY_OPEN
0x07 0x0075	键盘帮助键	0x008a	KEY_HELP
0x07 0x0076	键盘菜单键	0x0082	KEY_PROPS
0x07 0x0077	键盘 Select 键	0x0084	KEY_FRONT
0x07 0x0078	键盘 Stop 键	0x0080	KEY_STOP	3.0	0x0056	KEYCODE_MEDIA_STOP
0x07 0x0079	键盘 Again 键	0x0081	KEY_AGAIN
0x07 0x007a	键盘 Undo 键	0x0083	KEY_UNDO
0x07 0x007b	键盘 Cut 键	0x0089	KEY_CUT
0x07 0x007c	键盘 Copy 键	0x0085	KEY_COPY
0x07 0x007d	键盘 Paste 键	0x0087	KEY_PASTE
0x07 0x007e	键盘 Find 键	0x0088	KEY_FIND
0x07 0x007f	键盘 Mute 键	0x0071	KEY_MUTE	3.0	0x00a4	KEYCODE_VOLUME_MUTE
0x07 0x0080	键盘音量调高键	0x0073	KEY_VOLUMEUP	1.6	0x0018	KEYCODE_VOLUME_UP
0x07 0x0081	键盘音量调低键	0x0072	KEY_VOLUMEDOWN	1.6	0x0019	KEYCODE_VOLUME_DOWN
0x07 0x0082	键盘锁定 Caps Lock 键
0x07 0x0083	键盘锁定 Num Lock 键
0x07 0x0084	键盘锁定 Scroll Lock 键
0x07 0x0085	小键盘逗号键	0x0079	KEY_KPCOMMA	3.0	0x009f	KEYCODE_NUMPAD_COMMA
0x07 0x0086	小键盘等号键
0x07 0x0087	键盘 International1	0x0059	KEY_RO
0x07 0x0088	键盘 International2	0x005d	KEY_KATAKANAHIRAGANA
0x07 0x0089	键盘 International3	0x007c	KEY_YEN
0x07 0x008a	键盘 International4	0x005c	KEY_HENKAN
0x07 0x008b	键盘 International5	0x005e	KEY_MUHENKAN
0x07 0x008c	键盘 International6	0x005f	KEY_KPJPCOMMA
0x07 0x008d	键盘 International7
0x07 0x008e	键盘 International8
0x07 0x008f	键盘 International9
0x07 0x0090	键盘 LANG1	0x007a	KEY_HANGEUL
0x07 0x0091	键盘 LANG2	0x007b	KEY_HANJA
0x07 0x0092	键盘 LANG3	0x005a	KEY_KATAKANA
0x07 0x0093	键盘 LANG4	0x005b	KEY_HIRAGANA
0x07 0x0094	键盘 LANG5	0x0055	KEY_ZENKAKUHANKAKU
0x07 0x0095	键盘 LANG6
0x07 0x0096	键盘 LANG7
0x07 0x0097	键盘 LANG8
0x07 0x0098	键盘 LANG9
0x07 0x0099	键盘 Alternate Erase 键
0x07 0x009a	Keyboard SysReq/Attention key
0x07 0x009b	Keyboard Cancel key
0x07 0x009c	Keyboard Clear key
0x07 0x009d	Keyboard Prior key
0x07 0x009e	Keyboard Return key
0x07 0x009f	Keyboard Separator key
0x07 0x00a0	Keyboard Out key
0x07 0x00a1	Keyboard Opera key
0x07 0x00a2	Keyboard Clear/Again key
0x07 0x00a3	Keyboard CrSel/Props keys
0x07 0x00a4	Keyboard ExSel keys
0x07 0x00b0	Numpad 00
0x07 0x00b1	Numpad 000
0x07 0x00b2	thousands separator
0x07 0x00b3	decimal separator
0x07 0x00b4	Currency Unit
0x07 0x00b5	currency subunit
0x07 0x00b6	numpad (key	0x00b3	KEY_KPLEFTPAREN	3.0	0x00a2	KEYCODE_NUMPAD_LEFT_PAREN
0x07 0x00b7	numpad) keys	0x00b4	KEY_KPRIGHTPAREN	3.0	0x00a3	KEYCODE_NUMPAD_RIGHT_PAREN
0x07 0x00b8	numpad {keys
0x07 0x00b9	Keypad} key
0x07 0x00ba	Keyboard Tab key
0x07 0x00bb	Numpad Backspace key
0x07 0x00bc	Keypad A key
0x07 0x00bd	Numpad B key
0x07 0x00be	Numpad C key
0x07 0x00bf	D key on the small keyboard
0x07 0x00c0	Keypad E key
0x07 0x00c1	Numpad F key
0x07 0x00c2	Numpad XOR key
0x07 0x00c3	Numpad ^ key
0x07 0x00c4	Numpad % key
0x07 0x00c5	Numpad< key
0x07 0x00c6	Keypad > Keys
0x07 0x00c7	Keypad & Keys
0x07 0x00c8	Numpad && keys
0x07 0x00c9	keypad | key
0x07 0x00ca	Keyboard|| key
0x07 0x00cb	Numpad: keys
0x07 0x00cc	Keypad # key
0x07 0x00cd	Small keyboard space bar
0x07 0x00ce	Numpad @ key
0x07 0x00cf	Numpad! key
0x07 0x00d0	Numpad Memory Store key
0x07 0x00d1	Numpad Memory Recall key
0x07 0x00d2	Keypad Memory Clear key
0x07 0x00d3	Numpad Memory Add key
0x07 0x00d4	Numpad Memory Subtract key
0x07 0x00d5	Keypad Memory Multiply key
0x07 0x00d6	Numpad Memory Divide key
0x07 0x00d7	Numpad +/- keys
0x07 0x00d8	Keyboard Clear key
0x07 0x00d9	Keyboard Clear Entry key
0x07 0x00da	Keypad binary numbers
0x07 0x00db	Keypad octal number
0x07 0x00dc	Keypad decimal numbers
0x07 0x00dd	Keypad hexadecimal numbers
0x07 0x00e0	Keyboard left Ctrl key	0x001d	KEY_LEFTCTRL	3.0	0x0071	KEYCODE_CTRL_LEFT
0x07 0x00e1	Keyboard left shift key	0x002a	KEY_LEFTSHIFT	1.6	0x003b	KEYCODE_SHIFT_LEFT
0x07 0x00e2	Keyboard left Alt key	0x0038	KEY_LEFTALT	1.6	0x0039	KEYCODE_ALT_LEFT
0x07 0x00e3	Keyboard left GUI key	0x007d	KEY_LEFTMETA	3.0	0x0075	KEYCODE_META_LEFT
0x07 0x00e4	Keyboard right Ctrl key	0x0061	KEY_RIGHTCTRL	3.0	0x0072	KEYCODE_CTRL_RIGHT
0x07 0x00e5	Keyboard right Shift key	0x0036	KEY_RIGHTSHIFT	1.6	0x003c	KEYCODE_SHIFT_RIGHT
0x07 0x00e6	Keyboard right Alt key	0x0064	KEY_RIGHTALT	1.6	0x003a	KEYCODE_ALT_RIGHT
0x07 0x00e7	Keyboard right GUI key	0x007e	KEY_RIGHTMETA	3.0	0x0076	KEYCODE_META_RIGHT
0x07 0x00e8		0x00a4	KEY_PLAYPAUSE	3.0	0x0055	KEYCODE_MEDIA_PLAY_PAUSE
0x07 0x00e9		0x00a6	KEY_STOPCD	3.0	0x0056	KEYCODE_MEDIA_STOP
0x07 0x00ea		0x00a5	KEY_PREVIOUSSONG	3.0	0x0058	KEYCODE_MEDIA_PREVIOUS
0x07 0x00eb		0x00a3	KEY_NEXTSONG	3.0	0x0057	KEYCODE_MEDIA_NEXT
0x07 0x00ec		0x00a1	KEY_EJECTCD	3.0	0x0081	KEYCODE_MEDIA_EJECT
0x07 0x00ed		0x0073	KEY_VOLUMEUP	1.6	0x0018	KEYCODE_VOLUME_UP
0x07 0x00ee		0x0072	KEY_VOLUMEDOWN	1.6	0x0019	KEYCODE_VOLUME_DOWN
0x07 0x00ef		0x0071	KEY_MUTE	3.0	0x00a4	KEYCODE_VOLUME_MUTE
0x07 0x00f0		0x0096	KEY_WWW	1.6	0x0040	KEYCODE_EXPLORER
0x07 0x00f1		0x009e	KEY_BACK	1.6	0x0004	KEYCODE_BACK
0x07 0x00f2		0x009f	KEY_FORWARD	3.0	0x007d	KEYCODE_FORWARD
0x07 0x00f3		0x0080	KEY_STOP	3.0	0x0056	KEYCODE_MEDIA_STOP
0x07 0x00f4		0x0088	KEY_FIND
0x07 0x00f5		0x00b1	KEY_SCROLLUP	3.0	0x005c	KEYCODE_PAGE_UP
0x07 0x00f6		0x00b2	KEY_SCROLLDOWN	3.0	0x005d	KEYCODE_PAGE_DOWN

Here is a link to Google’s official instructions: 

Keyboard device | Android Open Source Project | Android Open Source Project