How to handle multi-keycode keys on Android with a bluetooth keyboard?

Question

I have a Microsoft Mobile Wedge keyboard. I've connected it to my Nexus 9 and after setting the language in the settings it works almost perfectly. Almost! There are 4 keys on it that don't work, because they're multi-keycode keys. They're the "magnifier glass"-key, the "3 dots on a ring"-key, the "black rectangle intersecting with rectangle border"-key and the "gears/settings"-key.

So far I've found out with

getevent -lt /dev/input/event4

that the Linux keycodes they send are

KEY_LEFTSHIFT
KEY_LEFTMETA
KEY_F21

KEY_LEFTALT
KEY_LEFTMETA
KEY_F21

KEY_LEFTCTRL
KEY_LEFTMETA
KEY_F21

KEY_LEFTMETA
KEY_F21

I've created the 2 files from their Generic.kl and Generic.kcm counterparts

/system/usr/keylayout/Vendor_045e_Product_0790.kl
/system/usr/keychars/Vendor_045e_Product_0790.kcm

and made sure with

dumpsys input

that they're used.

I tried to enable F21 in the layout first, but that didn't work because there's no Android keycode for F21. So I bound it to INSERT instead, because it's an unused key. Then I went into the character map and tried making an INSERT key (which is actually F21) and applying the right modifiers to it.

key INSERT {
    base:           'a'
    lmeta:          'A'
}

The above being for the key that only had 2 keycodes. Unfortunately this didn't work. Nothing happened. So now I'm here to pick your brain.

Does anyone know how to do multi-keycode keys?

Thank you very much in advance.

Answer 1

Do the following:

1. Run getevent without the -lt flag.

2. Press the key you want to test a few times. You'll get three lines something like:

   /dev/input/eventn: 0004 0004 longnum
   /dev/input/eventn: 0001 4_DIGIT_NUMBER_OF_INTEREST MASK
   /dev/input/eventn: 0000 0000 longemptynum

   The 4_DIGIT_NUMBER_OF_INTEREST is the scan-code.

3. In your .kl file (in /system/usr/keylayout/[yourlayout].kl), add a line:

   key [4_DIGIT_NUMBER_OF_INTEREST] [UNUSED_BINDING] 
   

   You've already gotten that far.

   So, in your .kcm file, you put the following lines and you should be good to go.

   key [UNUSED_BINDING] {
   lmeta:            what_you_want_for_just_lmeta (but it should be first)
   lshift+lmeta:     what_you_want_for_lshift+lmeta
   lalt+lmeta:       what_you_want_for_lalt+lmeta
   lctrl+lmeta:      what_you_want_for_lctrl+lmeta
   }

Reference: Key Character Map Files (under Key Declarations → Properties)

Answer 2

I am not sure if your way works or not, but try and see if this works. I have linked all the necessary stuff, have a look and try and se if it works.

Android Keyboard Devices (Scroll to the bottom of the page for all the key codes)

Keytest Apk (Use to show keycodes when pressed)

How to map android keys to your USB/Bluetooth Keyboard

Map android keys to any Keyboard

Android key Maps (User Blog)

Keyboard shortcuts and navigation, these may help with your problem or not (also extras for users who are reading this)

• ESC = go back
• CTRL + ESC = menu
• CTRL + ALT + DEL = restart (no questions asked)
• ALT + SPACE = search page (say “OK Google” to voice search)
• ALT + TAB (ALT + SHIFT + TAB) = switch tasks

Also, if you have designated volume function keys, those will probably work too. There’s also some dedicated app shortcuts like calculator, Gmail, and a few others:

Android Keyboard Shortcuts: Apps

• CMD (Windows key) + A = calculator
• CMD + C = contacts
• CMD + E = e-mail
• CMD + G = Gmail
• CMD + L = Calendar
• CMD + P = Play Music
• CMD + Y = YouTube

Others keys that are useful include:

Android Keyboard Shortcuts: Scrolling

• Spacebar: Page down in any Web page/document view
• Shift + Spacebar: Page up in any Web page/document view

Android Keyboard Shortcuts: Typing

• Alt + Spacebar: Insert a special character

• Shift + Del: Delete the character to the right of the cursor

• Alt + Del: Delete an entire line

• Shift + Shift (press it twice): Activate caps-lock; press shift once more to exit

• Alt + Trackball (Mouse) -Left: Move cursor to beginning of line

• Alt + Trackball-Right: Move cursor to end of line

• Alt + Trackball-Up: Move cursor to top of page

• Alt + Trackball-Down: Move cursor to bottom of page

• Shift + Trackball-Left/Right: Highlight text for cutting or copying

• Menu + X: Cut text (will cut all text on-screen unless specific characters are highlighted)

• Menu + C: Copy text to clipboard (will copy all text on-screen unless specific characters are highlighted)

• Menu + V: Paste text from clipboard

• Menu + A: Select all text in the current field

Android Keyboard Shortcuts: Browsing

• Menu + I: Zoom in

• Menu + O: Zoom out

• Menu + J: Go back a page

• Menu + K: Go forward a page

• Menu + R: Refresh current page

• Menu + F: Find on page

• Menu + B: Open bookmarks

• Menu + S: Open social network sharing menu

• Menu + H: View browsing history

• Menu + S: Open browser settings

Android Keyboard Shortcuts: Gmail

• F: Forward current message (works only while inside the message)

• R: Reply to current message (works only while inside the message)

• A: Reply-all to current message (works only while inside the message)

• Y: Archive message (works from within message or while on main inbox list)

• Menu + U: Refresh inbox

• Menu + C: Compose new e-mail

• Enter: Open an e-mail (from the main inbox list)

• Alt + Trackball-Up: Jump to top of inbox

• Alt + Trackball-Down: Jump to bottom of inbox