I'm trying to handle the event when a user presses "ok" or "cancel" on the automatic permission dialog presented when I connect a "known" USB device to the android phone.
I'm using the android.usb.host library and can send and receive between the android phone and the device. Futhermore do I handle the "USB_DEVICE_ATTACHED" and "USB_DEVICE_DETACHED" using a BroadcastReceiver without any problems.
I want to enable a sort of "autoconnect" feature and therefore I need to know when the user has pressed "ok" in the automatically displayed permission dialog, but I can't find anything online at all. All I find is "bypass dialog", but this is not what I want or need.
When I connect the usb device to the android phone, a permission dialog is automatically displayed because I use the "device_filter.xml" solution from androids documentation which can be seen here Android Usb Docs.
This is how I handle the USB_DEVICE_ATTATCHED and USB_DEVICE_DETACHED events:
public NativeUsbService(ReactApplicationContext reactContext) {
...
// register device attached/detached event listeners
IntentFilter filter = new IntentFilter();
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
reactContext.registerReceiver(usbReceiver, filter);
...
}
And then the Broadcast Receiver:
private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (action.equals(UsbManager.ACTION_USB_DEVICE_ATTACHED)) {
synchronized (this) {
UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if(device != null){
usbDevice = device;
} else {
Log.d(TAG, "onReceive: DEVICE WAS ATTACHED AND WAS NULL :(");
}
}
} else if (action.equals(UsbManager.ACTION_USB_DEVICE_DETACHED)) {
Log.d(TAG, "onReceive: Device was detached!");
if(connection != null) {
connection.releaseInterface(usbDeviceInterface);
connection.close();
}
connection = null;
usbDevice = null;
endpointIn = null;
endpointOut = null;
}
}
};
I have tried multiple different approaches, but nothing has worked.
I have tried getting the user response in from the intent, like with a manual permission request like below:
private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (action.equals(UsbManager.ACTION_USB_DEVICE_ATTACHED)) {
synchronized (this) {
UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if(device != null){
usbDevice = device;
// THIS DOES NOT WORK ↓↓↓
if(intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
// The code never gets here...
}
} else {
Log.d(TAG, "onReceive: DEVICE WAS ATTACHED AND WAS NULL :(");
sendEvent("onDeviceAttached", false);
}
}
} else if (action.equals(UsbManager.ACTION_USB_DEVICE_DETACHED)) {
if(connection != null) {
connection.releaseInterface(usbDeviceInterface);
connection.close();
}
connection = null;
usbDevice = null;
endpointIn = null;
endpointOut = null;
}
}
};
I have also tried by adding a usb permission listener to the broadcast receiver by first adding the action name to my class variables:
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
Then adding the action to my intent filter like so:
public NativeUsbService(ReactApplicationContext reactContext) {
// register device attached/detached event listeners
IntentFilter filter = new IntentFilter();
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
filter.addAction(ACTION_USB_PERMISSION); // added action to my intent filter
reactContext.registerReceiver(usbReceiver, filter);
}
And finally reacting to the action like so:
private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (action.equals(UsbManager.ACTION_USB_DEVICE_ATTACHED)) {
synchronized (this) {
UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if(device != null){
usbDevice = device;
}
}
} else if (action.equals(UsbManager.ACTION_USB_DEVICE_DETACHED)) {
Log.d(TAG, "onReceive: Device was detached!");
if(connection != null) {
connection.releaseInterface(usbDeviceInterface);
connection.close();
}
connection = null;
usbDevice = null;
endpointIn = null;
endpointOut = null;
sendEvent("onDeviceDetached", true);
}
else if (action.equals(ACTION_USB_PERMISSION)) {
Log.d(TAG, "onReceive: ACTION_USB_PERMISSION");
if(intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
Log.d(TAG, "onReceive: EXTRA_PERMISSION_GRANTED = true");
} else Log.d(TAG, "onReceive: EXTRA_PERMISSION_GRANTED = false");
}
}
};
Please make me aware of any missing information.
Any help is greatly appreciated.
Answering my own question in case someone else is facing the same issue.
I though about manually requesting the permission again, after permission was granted, since it is possible to handle this manual permission request when user presses an option in the dialog. I discarded this idea, not because it wouldn't work, but because I saw it as unecessary for the user to also have to press another dialog after the initial (automatic dialog).
I must add that I have not implemented this solution, so I do not know with certainty that it would prompt the user again, but I have had trouble with the manual permission request previously. If you want to try this approach the method belongs to the UsbManager class and is invoke like so usbManger.requestPermission(usbDevice).
I ended up with a solution where I start a thread which runs a loop calling usbManager.hasPermission(usbDevice) until it has permission and then emits an event (emitting this event is my use case, implement it how you like).
The solution can be seen here:
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbManager;
import com.facebook.react.bridge.ReactApplicationContext;
...
private static volatile boolean permissionThreadShouldStop = false;
private static Thread activePermissionThread = null;
...
public static void usbPermissionEventEmitter(ReactApplicationContext reactContext, UsbManager usbManager, UsbDevice usbDevice) {
if((activePermissionThread != null && activePermissionThread.isAlive())) {
activePermissionThread.interrupt();
}
permissionThreadShouldStop = false;
activePermissionThread = new Thread(new Runnable() {
#Override
public void run() {
while (!usbManager.hasPermission(usbDevice) && !permissionThreadShouldStop) {
try {
Thread.sleep(30);
} catch (InterruptedException e) {
e.printStackTrace();
break;
}
}
if(usbManager.hasPermission(usbDevice)) {
sendEvent(reactContext, "onUsbPermissionGranted", true);
}
}
});
activePermissionThread.start();
}
The ReactApplicationContext can be swapped with the normal android context. But this is for a react native module, so I use the reactContext.
I hope this will be helpful for someone, because i'm honestly really surpriced how scarse the android documentation is in regards to implementing Usb functionality using the android.hardware.usb library.
Also in general when searching for information online, I have often found myself lost since there is very little information on this subject.
I am a complete novice in Java and Android. I am trying to create a test app to listen for BLE and BT devices nearby. I have another device where I wrote some logic to broadcast its BLE beacons. I verified it using a playstore app. Now I am trying to write my own app on Android.
I have been reading the Android developer pages for guidance. I have literally followed every step of the following pages
https://developer.android.com/guide/topics/connectivity/bluetooth/setup
https://developer.android.com/guide/topics/connectivity/bluetooth/permissions
https://developer.android.com/guide/topics/connectivity/bluetooth/find-bluetooth-devices
https://developer.android.com/guide/topics/connectivity/bluetooth/find-ble-devices
Also, Note that I have used BARE MINIMUM CODE from the Android Developers page So here is what I have done.
1. First off I have added my permissions under AndroidManifest
Note1 : I am deploying this app to My phone running Android 11
Note2 : All this code is written inside MainActivity. I have not created any other activity class
<uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
<uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
2. Next I check if my BT is enabled.
if (bluetoothAdapter == null) {
blefinder.append("\nDEVICE DOES NOT SUPPORT BLUETOOTH");
}
else {
blefinder.append("\nDEVICE SUPPORTS BLUETOOTH");
}
I get the success message that BT is of course enabled
3. Next I check if my device supports BLE
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
blefinder.append("\nBLE NOT SUPPORTED ON THIS DEVICE : ");
finish();
}
else{
blefinder.append("\nBLE IS SUPPORTED ON THIS DEVICE : ");
}
I get the message that BLE is supported
4. Next I list my already paired/bonded devices
For this I call ListPairedAndBondedDevices(); in onCreate() itself right after the above steps. Function Definition Below.
private void ListPairedAndBondedDevices(){
#SuppressLint("MissingPermission") Set<BluetoothDevice> pairedDevices = bluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
// There are paired devices. Get the name and address of each paired device.
blefinder.append("\nPAIRED/BONDED DEVICES");
for (BluetoothDevice device : pairedDevices) {
blefinder.append("\n" + device.getName() + " | " + device.getAddress());
}
}
}
This also works like a charm and prints out my paired devices. The next 2 parts is where I face the problem.
5. The Problem Step | Part 1:
Here I register a Broadcast receiver to discover all BT devices in the vicinity. I've unbonded my BT headphones and kept it in pairing mode to verify this.
ListPairedAndBondedDevices(); // From previous code snippet
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); // New code statement
registerReceiver(BTReceiver, filter);// New code statement
Broadcast Receiver implementation
private final BroadcastReceiver BTReceiver = new BroadcastReceiver() {
#SuppressLint("MissingPermission")
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Discovery has found a device. Get the BluetoothDevice
// object and its info from the Intent.
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
blefinder.append("\n" + device.getName() + " | " + device.getAddress());
}
}
};
So This part didn't Work :(
If you see above, I am registering the BTReceiver in onCreate right after listing the already paired devices (by calling ListPairedAndBondedDevices()).
When I ran the debugger, this broadcast receiver never gets called.
6. The Problem Step | Part 2:
Right after this I try to scan for BLE Devices as well by callin scanLeDevice()
ListPairedAndBondedDevices(); // From previous snippet
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); // From previous snippet
registerReceiver(BTReceiver, filter);// From previous snippet
scanLeDevice(); // ---------------->>> CALLING THIS FUNCTION TO SCAN FOR BLE DEVICES
Implementation of scanLeDevice()
private void scanLeDevice() {
if (!scanning) {
// Stops scanning after a predefined scan period.
handler.postDelayed(new Runnable() {
#Override
public void run() {
scanning = false;
bluetoothLeScanner.stopScan(leScanCallback);
blefinder.append("\nSTOPPING BLE SCAN... TIMEOUT REACHED");
}
}, SCAN_PERIOD);
scanning = true;
bluetoothLeScanner.startScan(leScanCallback);
} else {
scanning = false;
bluetoothLeScanner.stopScan(leScanCallback);
blefinder.append("\nSTOPPING BLE SCAN");
}
}
Unfortunately this also fails. The debugger tells me that this part of the code is getting called.
And after 30 seconds of SCAN_PERIOD (The TIMEOUT that I've set), I get the message that the scanning has stopped (STOPPING BLE SCAN)
Now I have implemented the leScanCallback as well (i.e the Device Scan Callback)
private ScanCallback leScanCallback =
new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
super.onScanResult(callbackType, result);
blefinder.append("SOMETHING GOT SCANNED?");
blefinder.append("\n"+result.getDevice().toString());
// leDeviceListAdapter.addDevice(result.getDevice());
// leDeviceListAdapter.notifyDataSetChanged();
}
};
Notice that I am not using a ListAdapter since I have no idea about that concept. Hence for starters I am just trying to dump the results in a TextView represented by blefinder . This blefinder prints all the other texts so there is nothing wrong with that TextView variable. When I ran using the, debugger, it is not entering into the leScanCallback piece of code definition at all, even after 30 seconds, after scanLeDevice() function is executed.
I am a little lost here. Is there something I may be missing or doing wrong. It is supposed to be a simple, list the ble/bt devices around my vicinity.
I am happy to share any further information if I have missed. Just let me know in the comments.
Assuming you've done with the permissions that I've mentioned in the comments, we can implement a clean bluetooth LE scanner object and then use it in the UI.
First we implement a result consumer interface in order to deliver the results to the consumers which call the BleScanner.scan() method.
public interface ScanResultConsumer {
public void onDeviceFound(BluetoothDevice device, byte[] scanRecord, int rssi);
public void onScanningStarted();
public void onScanningStopped();
}
Now we need to implement the scanner object that manages the scanning events:
public class BleScanner {
private static final String TAG = BleScanner.class.getSimpleName();
private BluetoothLeScanner leScanner = null;
private BluetoothAdapter bleAdapter = null;
private Handler uiHandler = new Handler(Looper.getMainLooper);
private ScanResultConsumer scanResultConsumer;
private boolean scanning = false;
private final ArrayList<BluetoothDevice> foundDeviceList = new ArrayList<>();
public BleScanner(Context context) {
final BluetoothManager bluetoothManager = (BluetoothManager)
context.getSystemService(Context.BLUETOOTH_SERVICE);
bleAdapter = bluetoothManager.getAdapter();
if(bleAdapter == null) {
Log.d(TAG, "No bluetooth hardware.");
}
else if(!bleAdapter.isEnabled()){
Log.d(TAG, "Blutooth is off.");
}
}
public void scan(ScanResultConsumer scanResultConsumer, long scanTime){
foundDeviceList.clear();
if (scanning){
Log.d(TAG, "Already scanning.");
return;
}
Log.d(TAG, "Scanning...");
if(leScanner == null){
leScanner = bleAdapter.getBluetoothLeScanner();
}
if(scanTimeMs > 0) {
uiHandler.postDelayed(()-> {
if (scanning) {
Log.d(TAG, "Scanning is stopping.");
if(leScanner != null)
leScanner.stopScan(scanCallBack);
else
Log.d(TAG,"Scanner null");
setScanning(false);
}
}, scanTimeMs);
}
this.scanResultConsumer = scanResultConsumer;
leScanner.startScan(scanCallBack);
setScanning(true);
}
private final ScanCallback scanCallBack = new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
super.onScanResult(callbackType, result);
if (!scanning){
return;
}
if(foundDeviceList.contains(result.getDevice())) {
// This device has already been found
return;
}
// New device found, add it to the list in order to prevent duplications
foundDeviceList.add(result.getDevice());
if(scanResultConsumer != null) {
uiHandler.post(() -> {
scanResultConsumer.onDeviceFound(result.getDevice(),
result.getScanRecord().getBytes(), result.getRssi());
});
}
}
};
public boolean isScanning(){
return scanning;
}
void setScanning(boolean scanning){
this.scanning = scanning;
uiHandler.post(() -> {
if(scanResultConsumer == null) return;
if(!scanning){
scanResultConsumer.onScanningStopped();
// Nullify the consumer in order to prevent UI crashes
scanResultConsumer = null;
} else{
scanResultConsumer.onScanningStarted();
}
});
}
}
Finally we can use this clean implementation in anywhere we need. But do note that a context must be provided in order to create a BleScanner object.
public class MainActivity extends AppCompatActivity {
private BleScanner bleScanner;
private Button buttonScan
// Other codes...
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Other codes...
bleScanner = new BleScanner(getApplicationContext());
// Other codes...
// For example if you want to start scanning on a button press
// Let's say you have a button called buttonScan and initiated it
buttonScan = findViewById(R.id.scan_button);
buttonScan.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
bleScanner.scan(new ScanResultConsumer {
#Override
public void onDeviceFound(BluetoothDevice device, byte[] scanRecord, int rssi) {
// TODO Here you have a newly found device, do something.
}
#Override
q public void onScanningStarted() {
// TODO Scanning has just started, you may want to make some UI changes.
}
#Override
public void onScanningStopped() {
// TODO Scanning has just stopped, you may want to make some UI changes.
}
});
}
});
}
}
Note: I written this code in a plain editor not in Android Studio. So there may be some errors, let me know if any.
First you should check if your app was granted the location permission(s) in the Settings app > Apps <your_app> > permissions. Some permissions (like ACCESS_*_LOCATION and BLUETOOTH_ADMIN) need to be requested at runtime and granted by the user through a popup. Normally you should get a SecurityException or a logcat warning when trying to execute code requiring permissions which your app doesn't have, but it's not uncommon for android to skip over error handling.
Consider using this method to start the scan in order check its result code for potential additional info about what is (not) going on.
You might also get some clues by logging all actions received in BTReceiver.onReceive(), not just action found.
Lastly check if the location settings on your device to ensure that bluetooth scanning is turned on (Settings app > location > wifi and bluetooth scanning )
I know how to listen to volume buttons in an activity. But can I do that in a background service? If yes, how to do that?
It is possible. Use code below (for newer Android versions, especially Marshmallow, see bottom of the answer):
public class SettingsContentObserver extends ContentObserver {
int previousVolume;
Context context;
public SettingsContentObserver(Context c, Handler handler) {
super(handler);
context=c;
AudioManager audio = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
previousVolume = audio.getStreamVolume(AudioManager.STREAM_MUSIC);
}
#Override
public boolean deliverSelfNotifications() {
return super.deliverSelfNotifications();
}
#Override
public void onChange(boolean selfChange) {
super.onChange(selfChange);
AudioManager audio = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
int currentVolume = audio.getStreamVolume(AudioManager.STREAM_MUSIC);
int delta=previousVolume-currentVolume;
if(delta>0)
{
Logger.d("Ściszył!"); // volume decreased.
previousVolume=currentVolume;
}
else if(delta<0)
{
Logger.d("Zrobił głośniej!"); // volume increased.
previousVolume=currentVolume;
}
}
}
Then in your service onCreate register it with:
mSettingsContentObserver = new SettingsContentObserver(this,new Handler());
getApplicationContext().getContentResolver().registerContentObserver(android.provider.Settings.System.CONTENT_URI, true, mSettingsContentObserver );
Then unregister in onDestroy:
getApplicationContext().getContentResolver().unregisterContentObserver(mSettingsContentObserver);
Note that this example judges by change of media volume, if you want to use other volume, change it!
UPDATE:
Above method supposedly doesn't work on Marshmallow, BUT there's much better way now since MediaSession was introduced! So first you have to migrate your code to MediaController/MediaSession pattern and then use this code:
private VolumeProviderCompat myVolumeProvider = null;
myVolumeProvider = new VolumeProviderCompat(VolumeProviderCompat.VOLUME_CONTROL_RELATIVE, maxVolume, currentVolume) {
#Override
public void onAdjustVolume(int direction) {
// <0 volume down
// >0 volume up
}
};
mSession.setPlaybackToRemote(myVolumeProvider);
Somehow volume button presses are detected even with screen off (just be sure to register proper media button intent receiver if applicable for your platform!)
UPDATE 2 since GalDude requested some more info on getting media MediaSession/MediaController. Sorry, but since I stopped using Java it will be in Kotlin:
lateinit var mediaSession: MediaSessionCompat // you have to initialize it in your onCreate method
val kontroler: MediaControllerCompat
get() = mediaSession.controller // in Java it's just getController() on mediaSession
// in your onCreate/start method:
mediaSession = MediaSessionCompat(this, "YourPlayerName", receiver, null)
mediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS or MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS)
mediaSession.isActive = true
if (ratingIsWorking) // note: rating crashes on some machines you have to check it!
mediaSession.setRatingType(RatingCompat.RATING_5_STARS)
mediaSession.setCallback(object : MediaSessionCompat.Callback() {
...
// here you have to implement what happens with your player when play/pause/stop/ffw etc. is requested - see exaples elsewhere
})
// onDestroy/exit method:
mediaSession.isActive = false
mediaSession.release()
Unfortunately, this is another area of Android where there are like five different ways to "solve the problem", but most of them don't work very well. For my own sanity, I'll attempt to list all the different approaches below.
Solutions
1) MediaSession (from Service)
Answer by Denis Kniazhev: https://stackoverflow.com/a/43304591/2441655
Drawbacks:
Requires Android API level 21+ (Android 5.0+).
2) android.media.VOLUME_CHANGED_ACTION (from Service)
Answer by Nikhil: https://stackoverflow.com/a/44040282/2441655
Drawbacks:
Not an official part of the SDK: https://stackoverflow.com/a/8974510/2441655
Ignores first-press of volume-key (since it only shows the volume-bar).
Ignores volume-up key when at 100%, and volume-down key when at 0%.
3) ContentObserver (from Service)
Answer by ssuukk: https://stackoverflow.com/a/15292255/2441655 (first part)
Drawbacks:
Doesn't work in newer versions of Android: comment by dsemi
Ignores first-press of volume-key (since it only shows the volume-bar).
Ignores volume-up key when at 100%, and volume-down key when at 0%.
4) AudioManager.registerMediaButtonEventReceiver (from Service)
Answer by Joe: https://stackoverflow.com/a/11510564/2441655
Drawbacks:
Doesn't work on most roms: comment by elgui
5) onKeyDown (from Activity)
Answer by dipali: https://stackoverflow.com/a/21086563/2441655
Drawbacks:
Doesn't work if screen is off, in different app, etc.
6) dispatchKeyEvent (from Activity)
Answer by Maurice Gavin: https://stackoverflow.com/a/11462962/2441655
Drawbacks:
Doesn't work if screen is off, in different app, etc.
Conclusion
The solution I'm currently using is #1, because:
It's an official part of the SDK.
It is usable from a service. (ie. regardless of what app you're in)
It captures every volume-key press, regardless of current-volume/ui-state.
It works when the screen is off.
Let me know if you find any others -- or if you've found more drawbacks to some of them!
The AOSP Music app has a Service (MediaPlaybackService) that responds to volume key events by registering a BroadcastReceiver (MediaButtonIntentReceiver).
Here's the code snippet where it registers the receiver:
mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
ComponentName rec = new ComponentName(getPackageName(),
MediaButtonIntentReceiver.class.getName());
mAudioManager.registerMediaButtonEventReceiver(rec);
Also, don't forget about manifest:
<receiver android:name="com.android.music.MediaButtonIntentReceiver">
<intent-filter>
<action android:name="android.intent.action.MEDIA_BUTTON" />
<action android:name="android.media.AUDIO_BECOMING_NOISY" />
</intent-filter>
</receiver>
This works even if the Music app is not in the foreground. Isn't that what you want?
I was able to make it work on android 5+ devices using MediaSession. However,ContentObserver suggested by #ssuukk didn't work for me on both 4.4 and 7.0 devices (at least on ROMs that I've been testing on).
Here is a full example which works on android 5+.
Service:
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.support.v4.media.VolumeProviderCompat;
import android.support.v4.media.session.MediaSessionCompat;
import android.support.v4.media.session.PlaybackStateCompat;
public class PlayerService extends Service {
private MediaSessionCompat mediaSession;
#Override
public void onCreate() {
super.onCreate();
mediaSession = new MediaSessionCompat(this, "PlayerService");
mediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
.setState(PlaybackStateCompat.STATE_PLAYING, 0, 0) //you simulate a player which plays something.
.build());
//this will only work on Lollipop and up, see https://code.google.com/p/android/issues/detail?id=224134
VolumeProviderCompat myVolumeProvider =
new VolumeProviderCompat(VolumeProviderCompat.VOLUME_CONTROL_RELATIVE, /*max volume*/100, /*initial volume level*/50) {
#Override
public void onAdjustVolume(int direction) {
/*
-1 -- volume down
1 -- volume up
0 -- volume button released
*/
}
};
mediaSession.setPlaybackToRemote(myVolumeProvider);
mediaSession.setActive(true);
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onDestroy() {
super.onDestroy();
mediaSession.release();
}
}
In AndroidManifest.xml:
<application ...>
...
<service android:name=".PlayerService"/>
</application>
In your activity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
startService(new Intent(this, PlayerService.class));
}
There are several things to be aware of:
It intercepts volume buttons completely so while this code is running you won't be able to adjust ring volume using volume buttons. This might be possible to fix, I just didn't try.
If you run the example as-is the volume buttons will remain controlled by the app even when the screen is off and the app has been removed from "Recent Apps" list. You'll have to go to Settings->Applications, find the app and force stop it to get volume buttons back.
Judging by the couple of other questions about this topic, no.
Other question 1,
Other question 2
Services simply do not receive KeyEvent callbacks.
You need to play blank sound from service then only you can listen to volume changes. Following worked for me
Steps
1. Put blank.mp3 in raw folder (Download from here)
2. Start media at onStartCommand()
private MediaPlayer mediaPlayer;
public MyService() {
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
........
mediaPlayer = MediaPlayer.create(this, R.raw.blank);
mediaPlayer.setLooping(true);
mediaPlayer.start();
.......
return START_STICKY;
}
3. You must choose to stop and release mediaplayer. It's better to do so in onDestroy()
#Override
public void onDestroy() {
mediaPlayer.stop();
mediaPlayer.release();
super.onDestroy();
}
4. Create Broadcast receiver that will listen for volume changes
int volumePrev = 0;
private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
if ("android.media.VOLUME_CHANGED_ACTION".equals(intent.getAction())) {
int volume = intent.getIntExtra("android.media.EXTRA_VOLUME_STREAM_VALUE",0);
Log.i(TAG, "volume = " + volume);
if (volumePrev < volume) {
Log.i(TAG, "You have pressed volume up button");
} else {
Log.i(TAG, "You have pressed volume down button");
}
volumePrev = volume;
}
}
};
5. Register the broadcast receiver in onStartCommand()
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
.....
IntentFilter filter = new IntentFilter();
filter.addAction("android.media.VOLUME_CHANGED_ACTION");
registerReceiver(broadcastReceiver, filter);
....
return START_STICKY;
}
6. Unregister broadccast receiver in onDestroy()
#Override
public void onDestroy() {
.....
unregisterReceiver(broadcastReceiver);
.....
super.onDestroy();
}
That's all
This requires Lollipop (v5.0/API 21) or higher
My goal was to adjust system volume from a Service. Any action can be taken on press though.
public class VolumeKeyController {
private MediaSessionCompat mMediaSession;
private final Context mContext;
public VolumeKeyController(Context context) {
mContext = context;
}
private void createMediaSession() {
mMediaSession = new MediaSessionCompat(mContext, KeyUtil.log);
mMediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
mMediaSession.setPlaybackState(new Builder()
.setState(PlaybackStateCompat.STATE_PLAYING, 0, 0)
.build());
mMediaSession.setPlaybackToRemote(getVolumeProvider());
mMediaSession.setActive(true);
}
private VolumeProviderCompat getVolumeProvider() {
final AudioManager audio = mContext.getSystemService(Context.AUDIO_SERVICE);
int STREAM_TYPE = AudioManager.STREAM_MUSIC;
int currentVolume = audio.getStreamVolume(STREAM_TYPE);
int maxVolume = audio.getStreamMaxVolume(STREAM_TYPE);
final int VOLUME_UP = 1;
final int VOLUME_DOWN = -1;
return new VolumeProviderCompat(VolumeProviderCompat.VOLUME_CONTROL_RELATIVE, maxVolume, currentVolume) {
#Override
public void onAdjustVolume(int direction) {
// Up = 1, Down = -1, Release = 0
// Replace with your action, if you don't want to adjust system volume
if (direction == VOLUME_UP) {
audio.adjustStreamVolume(STREAM_TYPE,
AudioManager.ADJUST_RAISE, AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE);
}
else if (direction == VOLUME_DOWN) {
audio.adjustStreamVolume(STREAM_TYPE,
AudioManager.ADJUST_LOWER, AudioManager.FLAG_REMOVE_SOUND_AND_VIBRATE);
}
setCurrentVolume(audio.getStreamVolume(STREAM_TYPE));
}
};
}
// Call when control needed, add a call to constructor if needed immediately
public void setActive(boolean active) {
if (mMediaSession != null) {
mMediaSession.setActive(active);
return;
}
createMediaSession();
}
// Call from Service's onDestroy method
public void destroy() {
if (mMediaSession != null) {
mMediaSession.release();
}
}
}
#venryx: Solution 1 no longer works in Android 12
#ssuukk: I can confirm #venryx's comment that SettingsContentObserver does not get triggered if the volume is already at min or max.
#bikram: I created a VolumeButtonHelper class that uses this approach. Although it does use an undocumented SDK feature, it still works in 2022. I have extensively researched this topic and this was the only solution I could find.
class VolumeButtonHelper(private var context: Context,
private var stream: Int? = null,
enabledScreenOff: Boolean)
{
companion object
{
const val VOLUME_CHANGE_ACTION = "android.media.VOLUME_CHANGED_ACTION"
const val EXTRA_VOLUME_STREAM_TYPE = "android.media.EXTRA_VOLUME_STREAM_TYPE"
}
enum class Direction
{
Up,
Down,
Release
}
private lateinit var mediaPlayer: MediaPlayer
private var volumeBroadCastReceiver: VolumeBroadCastReceiver? = null
private var volumeChangeListener: VolumeChangeListener? = null
private val audioManager: AudioManager? =
context.getSystemService(Context.AUDIO_SERVICE) as? AudioManager
private var priorVolume = -1
private var volumePushes = 0.0
private var longPressReported = false
var doublePressTimeout = 350L
var buttonReleaseTimeout = 100L
var minVolume = -1
private set
var maxVolume = -1
private set
var halfVolume = -1
private set
var currentVolume = -1
private set
init
{
if (audioManager != null)
{
minVolume = audioManager.getStreamMinVolume(STREAM_MUSIC)
maxVolume = audioManager.getStreamMaxVolume(STREAM_MUSIC)
halfVolume = (minVolume + maxVolume) / 2
/*************************************
* BroadcastReceiver does not get triggered for VOLUME_CHANGE_ACTION
* if the screen is off and no media is playing.
* Playing a silent media file solves that.
*************************************/
if (enabledScreenOff)
{
mediaPlayer =
MediaPlayer.create(context,
R.raw.silence)
.apply {
isLooping = true
setWakeMode(context, PARTIAL_WAKE_LOCK)
start()
}
}
}
else
Log.e(TAG, "Unable to initialize AudioManager")
}
fun registerVolumeChangeListener(volumeChangeListener: VolumeChangeListener)
{
if (volumeBroadCastReceiver == null)
{
this.volumeChangeListener = volumeChangeListener
volumeBroadCastReceiver = VolumeBroadCastReceiver()
if (volumeBroadCastReceiver != null)
{
val filter = IntentFilter()
filter.addAction(VOLUME_CHANGE_ACTION)
context.registerReceiver(volumeBroadCastReceiver, filter)
}
else
Log.e(TAG, "Unable to initialize BroadCastReceiver")
}
}
fun unregisterReceiver()
{
if (volumeBroadCastReceiver != null)
{
context.unregisterReceiver(volumeBroadCastReceiver)
volumeBroadCastReceiver = null
}
}
fun onVolumePress(count: Int)
{
when (count)
{
1 -> volumeChangeListener?.onSinglePress()
2 -> volumeChangeListener?.onDoublePress()
else -> volumeChangeListener?.onVolumePress(count)
}
}
interface VolumeChangeListener
{
fun onVolumeChange(direction: Direction)
fun onVolumePress(count: Int)
fun onSinglePress()
fun onDoublePress()
fun onLongPress()
}
inner class VolumeBroadCastReceiver : BroadcastReceiver()
{
override fun onReceive(context: Context, intent: Intent)
{
if (stream == null ||
intent.getIntExtra(EXTRA_VOLUME_STREAM_TYPE, -1) == stream)
{
currentVolume = audioManager?.getStreamVolume(STREAM_MUSIC) ?: -1
if (currentVolume != -1)
{
if (currentVolume != priorVolume)
{
if (currentVolume > priorVolume)
volumeChangeListener?.onVolumeChange(Up)
else if (currentVolume < priorVolume)
volumeChangeListener?.onVolumeChange(Down)
priorVolume = currentVolume
}
volumePushes += 0.5 // For some unknown reason (to me), onReceive gets called twice for every button push
if (volumePushes == 0.5)
{
CoroutineScope(Dispatchers.Main).launch {
delay(doublePressTimeout - buttonReleaseTimeout)
buttonDown()
}
}
}
}
}
private fun buttonDown()
{
val startVolumePushes = volumePushes
CoroutineScope(Dispatchers.Main).launch {
delay(buttonReleaseTimeout)
val currentVolumePushes = volumePushes
if (startVolumePushes != currentVolumePushes)
{
if (volumePushes > 2 && !longPressReported)
{
longPressReported = true
volumeChangeListener?.onLongPress()
}
buttonDown()
}
else
{
onVolumePress(volumePushes.toInt())
volumeChangeListener?.onVolumeChange(Release)
volumePushes = 0.0
longPressReported = false
}
}
}
}
}
Instantiate that class in a Service (with the appropriate wake lock):
class ForegroundService : Service()
{
private lateinit var volumeButtonHelper: VolumeButtonHelper
companion object
{
var wakeLock: WakeLock? = null
const val TAG = "VolumeButtonHelper"
const val ACTION_FOREGROUND_WAKELOCK = "com.oliverClimbs.volumeButtonHelper.FOREGROUND_WAKELOCK"
const val ACTION_FOREGROUND = "com.oliverClimbs.volumeButtonHelper.FOREGROUND"
const val WAKELOCK_TAG = "com.oliverClimbs.volumeButtonHelper:wake-service"
const val CHANNEL_ID = "Running in background"
}
override fun onBind(p0: Intent?): IBinder?
{
return null
}
override fun onCreate()
{
super.onCreate()
volumeButtonHelper = VolumeButtonHelper(this,
STREAM_MUSIC,
enabledScreenOff = true)
volumeButtonHelper.registerVolumeChangeListener(
object : VolumeButtonHelper.VolumeChangeListener
{
override fun onVolumeChange(direction: VolumeButtonHelper.Direction)
{
Log.i(TAG, "onVolumeChange: $direction")
}
override fun onVolumePress(count: Int)
{
Log.i(TAG, "onVolumePress: $count")
}
override fun onSinglePress()
{
Log.i(TAG, "onSinglePress")
}
override fun onDoublePress()
{
Log.i(TAG, "onDoublePress")
}
override fun onLongPress()
{
Log.i(TAG, "onLongPress")
}
})
}
#SuppressLint("WakelockTimeout")
override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int
{
super.onStartCommand(intent, flags, startId)
if (intent?.action == ACTION_FOREGROUND || intent?.action == ACTION_FOREGROUND_WAKELOCK)
startForeground(R.string.foreground_service_started,
Notification.Builder(this, CHANNEL_ID).build())
if (intent?.action == ACTION_FOREGROUND_WAKELOCK)
{
if (wakeLock == null)
{
wakeLock = getSystemService(PowerManager::class.java)?.newWakeLock(
PARTIAL_WAKE_LOCK,
WAKELOCK_TAG)
wakeLock?.acquire()
}
else
{
releaseWakeLock()
}
}
return START_STICKY
}
private fun releaseWakeLock()
{
wakeLock?.release()
wakeLock = null
}
override fun onDestroy()
{
super.onDestroy()
releaseWakeLock()
stopForeground(STOP_FOREGROUND_REMOVE)
volumeButtonHelper.unregisterReceiver()
}
}
Start the Service from your Activity:
class MainActivity : AppCompatActivity()
{
private var configurationChange = false
override fun onCreate(savedInstanceState: Bundle?)
{
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
if (!configurationChange)
startService(Intent(ForegroundService.ACTION_FOREGROUND_WAKELOCK).setClass(this,
ForegroundService::class.java))
}
override fun onDestroy()
{
Log.d(TAG, "MainActivity: onDestroy")
configurationChange =
if (isChangingConfigurations)
true
else
{
stopService(Intent(this, ForegroundService::class.java))
false
}
super.onDestroy()
}
}
I have shared the full project at github.com/oliverClimbs/VolumeButtonDemo.
As for me accessibility service only works as expected
class KeyService : AccessibilityService() {
override fun onServiceConnected() {}
override fun onAccessibilityEvent(event: AccessibilityEvent) {}
override fun onKeyEvent(event: KeyEvent): Boolean {
when (event.keyCode) {
KeyEvent.KEYCODE_VOLUME_UP -> {
when (event.action) {
KeyEvent.ACTION_DOWN -> {
}
KeyEvent.ACTION_UP -> {
}
}
}
KeyEvent.KEYCODE_VOLUME_DOWN -> {
when (event.action) {
KeyEvent.ACTION_DOWN -> {
}
KeyEvent.ACTION_UP -> {
}
}
}
}
return super.onKeyEvent(event)
}
override fun onInterrupt() {}
}
<?xml version="1.0" encoding="utf-8"?>
<accessibility-service xmlns:android="http://schemas.android.com/apk/res/android"
android:accessibilityFlags="flagRequestFilterKeyEvents"
android:canRequestFilterKeyEvents="true"
android:description="#string/app_name" />
<service
android:name=".KeySrvice"
android:exported="true"
android:label="#string/app_name"
android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE">
<meta-data
android:name="android.accessibilityservice"
android:resource="#xml/key" />
<intent-filter>
<action android:name="android.accessibilityservice.AccessibilityService" />
</intent-filter>
</service>
inline fun <reified T : Service> Context.hasAccessibility(): Boolean {
var enabled = 1
try {
enabled = Secure.getInt(contentResolver, Secure.ACCESSIBILITY_ENABLED)
} catch (ignored: Throwable) {
}
if (enabled == 1) {
val name = ComponentName(applicationContext, T::class.java).flattenToString()
val services = Secure.getString(contentResolver, Secure.ENABLED_ACCESSIBILITY_SERVICES)
return services?.contains(name) ?: false
}
return false
}
if (!hasAccessibility<KeyService>()) {
startActivity(Intent(Settings.ACTION_ACCESSIBILITY_SETTINGS))
}
Android doesn't document APIs on interacting with volume buttons in that case. So I guess the answer is no…
checkout Controlling Your App’s Volume and Playback ...This will help to solve your problem... multiple applications might want to listen for button presses from background, this may be the reason why KeyEvents can only be handled by Activities as they are the interface to the user pressing the keys.
Note: this only works for Activities, and not Services as the question states.
Depending on the context in which the callback is required an alternative solution might be available.
To be capable of detecting the volume button an Activity would need to override the dispatchKeyEvent function. For this to be present in multiple activities could could write a superclass containing the overridden function which is extended by all subsequent activities.
Here is the code for detecting Volume Up/Down key presses:
// Over-ride this function to define what should happen when keys are pressed (e.g. Home button, Back button, etc.)
#Override
public boolean dispatchKeyEvent(KeyEvent event)
{
if (event.getAction() == KeyEvent.ACTION_DOWN)
{
switch (event.getKeyCode())
{
case KeyEvent.KEYCODE_VOLUME_UP:
// Volume up key detected
// Do something
return true;
case KeyEvent.KEYCODE_VOLUME_DOWN:
// Volume down key detected
// Do something
return true;
}
}
return super.dispatchKeyEvent(event);
}
Been googling around this problem 10 years later, and I dug out this here:
https://stackoverflow.com/a/59064820
By providing an AccessibilityService, it is possible to listen to the volume buttons, outside the activity, even when the phone is locked, even before it is sent down to the specific apps (just tested it). Only downside: The user must activate this service manually in the settings.
MyService.java
public class MyService extends Service {
private BroadcastReceiver vReceiver;
#Override
public void onCreate() {
super.onCreate();
vReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
FileLog.e("Something just happens");
}
};
registerReceiver(vReceiver, new IntentFilter("android.media.VOLUME_CHANGED_ACTION"));
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onDestroy() {
unregisterReceiver(vReceiver);
}
}
AndroidManifest.xml
<application>
...
<service android:name=".MyService" android:exported="true"/>
</application>
onCreate || onStartActivity
public void onCreate(){
....
startService(new Intent(this, MyService.class));
}
that solution like little bit same as Answer
but working on Android 33+
I am trying to discover all available bluetooth devices and pass to another activity.
However even when looking at the Android Docs, I am unable to figure out why I cannot discover any devices and my ArrayList remains empty.
OnClick execute this:
mBluetoothAdapter.startDiscovery();
My broadcast listener also works but nothing is every returned and ArrayList remains empty.
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
mDeviceList.add(device);
showToast("Found device " + device.getName());
}
if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR);
if (state == BluetoothAdapter.STATE_ON) {
showToast("Enabled");
showEnabled();
}
}
if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
mDeviceList = new ArrayList<>();
mProgressDlg.show();
}
if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
mProgressDlg.dismiss();
Intent newIntent = new Intent(MainScreen.this, DeviceListActivity.class);
if (mDeviceList.isEmpty()){
Log.d("onReceive: ", "EMPTY");
}
newIntent.putParcelableArrayListExtra("device.list", mDeviceList);
startActivity(newIntent);
}
}
};
GIST
Answered my own question.
The fix was to turn location on with app permissions.
Apparently this is required for Android Marshmallow
I'm currently making an app that adapt the volume depending on the bluetooth device you are connected to.
I am having issue when I want to change the volume of the music
My app detect when a bluetooth device is connected and it can change the volume but it is like it goes too quickly
Here is some of the code:
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
BluetoothDevice d = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
deviceConnected(d);
}
else if (BluetoothDevice.ACTION_ACL_DISCONNECTED.equals(action)) {
deviceDisconnected(d);
}
}
};
private void deviceConnected(BluetoothDevice bluetoothDevice) {
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
boolean showToasts = prefs.getBoolean("show_toasts", false);
if (showToasts) { Toast.makeText(this, getResources().getString(R.string.connected_to) + " " + bluetoothDevice.getName(), Toast.LENGTH_SHORT).show(); }
mDeviceDAO = new DeviceDAO(this);
mDeviceDAO.open();
DeviceOptions device = mDeviceDAO.select(bluetoothDevice.getAddress());
if (device == null) { return; }
if(device.getActivated() == 0) {
return;
}
int v = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
saveLastVolume(v);
int volume = device.getVolume();
int flag = 0;
if(prefs.getBoolean("show_am_ui", false)) {
flag = AudioManager.FLAG_SHOW_UI;
}
mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC,
volume,
flag);
}
If add a delay of around 3000ms when I change the volume, it will work properly but it's not a clean solution. In fact the toast for the connection will be displayed before the bluetooth device is "completely" connected
I also found an app that do the same thing but it seems that I'm doing the same thing.
Here is its githublink
What's your capture is the ACL connected or ACL disconnected, yes you are right once your toast appears i.e. the ACL connected does not mean the Bluetooth profile connected(exactly what you said "completely" connected), it only means the physical connection established between two device, you might as well to receive other event, e.g. HFP/A2dp connected, that's the real profile connected.
However the ACL disconnected is the milestone that the Bluetooth connection is really disconnected.