How to capture key events from bluetooth headset with android

Question

My app can be controlled by normal headset. It simply overrides "onKeyDown". But key events from bluetooth headset are not captured - why? Or how to capture bluetooth key events?

the "log cat" shows the following if i press button on headset:

Bluetooth AT recv(3043): AT+VGS=15
AudioPolicyManagerBase(13654): FM radio recording off
AudioService(2261): sendVolumeUpdate, isKeyguardLocked...Not to update Volume Panel.
VolumePanel(2261): change volume by MSG_VOLUME_CHANGED
VolumePanel(2261): onVolumeChanged(streamType: 6, flags: 0)
VolumePanel(2261): Call setChangeSeekbarColor(false)

i also tried to handle media button actions but this isn't working. my idea is a free configurable key mapping: the user chooses "set key" my app hears on all keys (hardware, media buttons, bluetooth headset) then the user presses a key and the event/key code is stored in config.

Summerizing not working Answers: Volume buttons must be captured by "VOLUME_CHANGED_ACTION". The problem is this intents are broadcasted to other apps and abortBroadcast() doesn't work (it works only for "ordered" Broadcasts). Another problem is that keys on cable headset and on phone trigger onReceive() twice (why?) the bluetooth headset trigger it once. The next Problem is the 3rd key on Bluetooth headset. It triggers voice-command (s-voice starts on s3), i tried to capture many different intents regarding this but i can't "receive" this button press and don't know why. At the end i want capture all kinds of buttons and don't want them handled by other apps (like using onKeyDown and returning true).

Answer 1

Add a broadcast listener to MEDIA_BUTTON:

<intent-filter android:priority="<some number>"> 
   <action android:name="android.intent.action.MEDIA_BUTTON" /> 
</intent-filter> 

You should register your broadcast receiver inside your application (not in manifest file). Otherwise Google Music player will catch your broadcast and aboard it.

Your IntentFilter priority should be higher that other media players priorities in your phone)

Add android.permission.BLUETOOTH permission in manifest to support Bluetooth headset

After received you key you have to manually abort the broadcast using abortBroadcast().

However priorities and abortBroadcast() work fine as long as each app only responds while e.g. something is played. But several users also expect a "default player" to be launched (or start playing) upon button press, like the default player, so it might happen some app with a higher priority number won't let the intent come through to your app

In the onReceive, you can get the button event with

KeyEvent key = (KeyEvent) 
intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT); 

key.getKeyAction() tells you whether the button was released or pressed, key.getKeyCode() tells which button is pressed.

If you want to handle single button cable headsets as well, also regard the key code KEYCODE_HEADSETHOOK

Override the onKeyDown method in any activity and check for the KeyEvent.KEYCODE_MEDIA_KEYCODE_pressed_key

e.g.

 boolean onKeyDown(int keyCode, KeyEvent event) { 
            AudibleReadyPlayer abc; 
            switch (keyCode) { 
            case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD: 
                    // code for fast forward 
                    return true; 
            case KeyEvent.KEYCODE_MEDIA_NEXT: 
                    // code for next 
                    return true; 
            case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE: 
                    // code for play/pause 
                    return true; 
            case KeyEvent.KEYCODE_MEDIA_PREVIOUS: 
                    // code for previous 
                    return true; 
            case KeyEvent.KEYCODE_MEDIA_REWIND: 
                    // code for rewind 
                    return true; 
            case KeyEvent.KEYCODE_MEDIA_STOP: 
                    // code for stop 
                    return true; 
            } 
            return false; 
    } 

Volume key integration example Android - Volume Buttons used in my application
This one may need permission

<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />

Or you can try slimier implementations over the following link

Android Developer Blog : Handling remote control buttons
Android Tales : Add Headset button support to your Android application

Answer 2

Check out this article. It explains how to implement something similar using media button actions.

I know you've mentioned that you walked this way without success, still give it a try. Point your attention to gotchas related to registering broadcast receiver, setting intent filter priorities and adding permissions (all explained in the article).

Hope this will help.