Develop Reference

Bluetooth devices found in an Android app, but not in a platform specific code in Flutter

I'm trying to scan, connect and receive data from a Bluetooth module. Everything works fine if I just use an android application. I can scan and find all nearby devices, connect to anyone (I'm only interested in my Bluetooth module) and I am able to read the test data that's being sent from the Bluetooth module.
The problem is that the application is being developed using Flutter. I used the same code from my Android application and linked it with Dart though the EventsChannel, but now I can only see fewer Bluetooth devices in the Flutter app and none of them is the Bluetooth Module I'm interested in. I'm new to Flutter and the platform specific coding, I can't understand why the same code behaves differently in different apps on same the hardware.
I've tested my code on Samsung S4 and S8 phones and the result is the same.
This is the code for the EventChannel for the discovery part:
new EventChannel(flutterEngine.getDartExecutor(), DISCOVER_CHANNEL).setStreamHandler(
new EventChannel.StreamHandler() {
#Override
public void onListen(Object args, EventChannel.EventSink events) {
Log.w(TAG, "Registering receiver");
discoverReceiver = DiscoverReceiver(events);
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(discoverReceiver, filter);
}
#Override
public void onCancel(Object args) {
Log.w(TAG, "Unregistering receiver");
unregisterReceiver(discoverReceiver);
discoverReceiver = null;
}
}
);
For now my discoverReceiver is a global BroadcastReceiver.
Below is the code for the Broadcastreceiver:
private BroadcastReceiver DiscoverReceiver(final EventSink events) {
return new BroadcastReceiver() {
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);
String deviceName = device.getName();
if (deviceName == null){
deviceName = "No Device Name";
}
events.success(deviceName);
Log.w(TAG, "Sending " + deviceName);
}
}
};
}
**I used the (Log.w(TAG, "Sending " + deviceName);) statement to see if events were being lost/dropped.
And below is how I receive it in Dart:
#override
void initState() {
super.initState();
devices.add(selectDevice);
discoverChannel.receiveBroadcastStream().listen(onEvent);
}
void onEvent(Object event) {
setState(() {
devices.add(event);
});
}
Below is the code in my Android app that can scan and find all devices in case you want to compare with the above:
private BroadcastReceiver DiscoverReceiver() {
return new BroadcastReceiver() {
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);
String deviceName = device.getName();
if (deviceName == null){
deviceName = "No Device Name";
}
devicelist.add(device);
devNames.add(deviceName);
arrayAdapter.add(deviceName);
arrayAdapter.notifyDataSetChanged();
Log.w(TAG, "Sending " + deviceName);
}
}
};
}
I'm not concerned with the last snippet but I just thought I'd show the complete flow. Snippet 2 is a copy of what I have in a stand-alone Android App and it scans and finds all devices, but once I use it in a Flutter App as native code for Android it stops finding the same number of devices, still finds some though and is very unreliable.
I have tried most of the Flutter bluetooth packages but none of them was what I was looking for and so I ended up going with Platform specific code, which worked fine until it was plugged to Flutter. I've read the documentation for Android development and the code above is mostly modified code from Android sample. I just can't figure out why the same code can find more devices as a stand-alone app versus using it as a native code for a flutter application if at the end it's being tested on the same hardware.
Any input will be appreciated!

Ok so I've finally found the solution. It is something to do with the Bluetooth's startDiscovery() running and doing its job properly but the events are captured a little later, something that the debugger would not be able to show.
So in my case, all devices were "discovered" but the flutter app starts capturing the events later so it only shows the last 1 or 2 devices that were discovered during the discovery.
I moved:
discoverChannel.receiveBroadcastStream().listen(onEvent);
From the initState() and into a function that is called after a button press, which makes sure everything has loaded before registering the broadcast receiver on the native side and the broadcast stream receiver on Dart's.
I'm still not sure exactly how to express this, but it's about the timing of registering the BroadcastReceiver on the native side and the receiveBroadcastStream on Dart's side.
Now it starts the discovery and captures the events properly, which shows the same number of devices found in an Android stand-alone app.
Hope this helps anyone who might face this odd issue in the future.

How to hide the pairing dialog box to programmatically pair a BLE device on Android?

I was trying to pair a BLE device programmatically from my android app.So at first I register a BroadcastReceiver for PAIRING_REQUEST.When device.createBond() is called ,the BroadcastReciever is triggered. When the BroadcastReciever is triggered, I set the passkey by using setpin(). But the problem is pairing request dialog box appeared sometimes and sometimes without appearing pairing box pairing is done automatically . I want that it will never show any dialog box but it should be paired with the passkey programmatically.
Any solution of it ?
Or is there any way to fulfill my expectation?
Thanks in advance.
Registered broadCasterReciever during application launching
IntentFilter intentFilter = new IntentFilter(BluetoothDevice.ACTION_PAIRING_REQUEST);
intentFilter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
appContext.getApplicationContext().registerReceiver(broadCastReceiver,intentFilter);
Implementation of broadcastReciever.
private String BLE_PIN= "000012";
private BroadcastReceiver broadCastReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if(BluetoothDevice.ACTION_PAIRING_REQUEST.equals(action))
{
BluetoothDevice bluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
bluetoothDevice.setPin(BLE_PIN.getBytes());
Log.e("TAG","Auto-entering pin: " + BLE_PIN);
}
}
};
And I called device.createBond() after discovering the device.

calling abortBroadcast(); after setPin() solved the problem for me.

How to get BLUETOOTH_PRIVILEGED permission to auto pair device in a routed device without putting it at system app?

I need BLUETOOTH PRIVILEGED permission to autopair device
How to get BLUETOOTH_PRIVILEGED permission to autopair device in a roted device
without putting it at system app ?
I am trying to make a programmatically auto repair with one devices that I have already displayed in ListView without showing the "Pair Dialog"
IntentFilter filter = new IntentFilter("android.bluetooth.device.action.PAIRING_REQUEST");
registerReceiver(new PairingRequest(), filter);
//receiver
public static class PairingRequest extends BroadcastReceiver {
public PairingRequest() {
super();
}
#Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals("android.bluetooth.device.action.PAIRING_REQUEST")) {
try {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
int pin = intent.getIntExtra("android.bluetooth.device.extra.PAIRING_KEY", 0);
//the pin in case you need to accept for an specific pin
Log.d("PIN", " " + intent.getIntExtra("android.bluetooth.device.extra.PAIRING_KEY",0));
//maybe you look for a name or address
Log.d("Bonded", device.getName());
byte[] pinBytes;
pinBytes = (""+pin).getBytes("UTF-8");
device.setPin(pinBytes);
device.setPairingConfirmation(true);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
but after is calling device.setPairingConfirmation(true); it goes on exception with this error java.lang.SecurityException: Need BLUETOOTH PRIVILEGED permission: Neither user 10069 nor current process has android.permission.BLUETOOTH_PRIVILEGED.
I have made my search and all the suggestions was to put the app in system/app but I can't put there cause I need to make updates in the future.
My device that I am using is rooted and the app is in "data/app" path
Any suggestion would be an help.
Thanks a lot!

Bring Bluetooth pairing request notification dialog on front to ask for PIN

What I'm trying to do is to brin the dialog to input the PIN for a pairing process.
After I connect to a device, I receive a notification but the pairing dialog does not show up. I have to open it manually.
So far I tried the following methods which are called in the broadcast receiver when I get the PAIRING_REQUEST action:
public void pairDevice(BluetoothDevice device)
{
String ACTION_PAIRING_REQUEST = "android.bluetooth.device.action.PAIRING_REQUEST";
Intent intent = new Intent(ACTION_PAIRING_REQUEST);
String EXTRA_DEVICE = "android.bluetooth.device.extra.DEVICE";
intent.putExtra(EXTRA_DEVICE, device);
String EXTRA_PAIRING_VARIANT = "android.bluetooth.device.extra.PAIRING_VARIANT";
int PAIRING_VARIANT_PIN = 0;
intent.putExtra(EXTRA_PAIRING_VARIANT, PAIRING_VARIANT_PIN);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
Which shows the dialog properly but after I input it, it does not pair my device.
I also tried this code:
public void pairDevice(BluetoothDevice device)
{
Intent intent = new Intent("android.bluetooth.device.action.PAIRING_REQUEST");
String EXTRA_DEVICE = "android.bluetooth.device.extra.DEVICE";
intent.putExtra(EXTRA_DEVICE, device);
int PAIRING_VARIANT_PIN = 272;
intent.putExtra("android.bluetooth.device.extra.PAIRING_VARIANT", PAIRING_VARIANT_PIN);
sendBroadcast(intent);
}
Which crashes my app because it says I don't have permissions to send broadcast for PAIRING_REQUEST (even if I set both permissions BLUETOOTH and BLUETOOTH_ADMIN)
Please, I really need to show this dialog and much better if it is the default one. I am connecting to a BLE device, and after connected it requires a PIN for pairing and be able to modify some characteristics.
Your help would be much appreciated!
Thanks in advance!

Try to use new Android BluetoothDevice API: bluetoothdevice.createBond(). After you call this method, the system will invoke the pairing request dialog for you automatically. Then you can enter PIN in that pop up dialog.
Consider adding something like this in your code, where you want to start the pairing process:
private void pairDevice(BluetoothDevice device) {
try {
Log.d(TAG, "Start Pairing... with: " + device.getName());
device.createBond();
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}

I had a similar issue, make sure your bluetooth user permissions are set within the manifest xml tag not under the application tag - in the AndroidManifest (that is). Hope this helps.

You can use connect method directly to pair the device.If the two devices have not been previously paired, then the Android framework will automatically show a pairing request notification or dialog to the user during the connection procedure. So when attempting to connect devices, your application does not need to be concerned about whether or not the devices are paired.

Try to use this for all API levels:
public static void pairDevice(BluetoothDevice device) {
try {
Method method = device.getClass().getMethod("createBond", (Class[]) null);
method.invoke(device, (Object[]) null);
//From API 19.
// device.createBond();
} catch (Exception e) {
e.printStackTrace();
}
}

How identify *which* bluetooth device causes an ACTION_ACL_CONNECTED broadcast?

I want to listen for connection/disconnection with a number of specific bluetooth devices whose MAC addresses I know, but which are not necessarily paired (I don't want to mess with the user's list of paired devices and vice versa). I'm only interested in discovering their presence, not communicating with them.
This works very well with my code below! But my problem is that I cannot find out which specific device is connecting/disconnecting, only that it happens to someone of them. How can I find out which one the action concerns?
First I instantiate objects for my two specific physical bluetooth devices and add them to my intent filter:
BluetoothDevice myPinkHeadset = mBluetoothAdapter.getRemoteDevice("18:17:0C:EB:9C:81");
BluetoothDevice myPcBluetoothDongle = mBluetoothAdapter.getRemoteDevice("5A:7A:CC:4B:C5:08");
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(myPinkHeadset.ACTION_ACL_CONNECTED);
intentFilter.addAction(myPinkHeadset.ACTION_ACL_DISCONNECTED);
intentFilter.addAction(myPcBluetoothDongle.ACTION_ACL_CONNECTED);
intentFilter.addAction(myPcBluetoothDongle.ACTION_ACL_DISCONNECTED);
Then I listen for broadcasts about them:
final BroadcastReceiver intentReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
Now I want to find out which one has been connected and/or disconnected, and I don't see how I can do that.
Either 1) I use "BluetoothDevice" directly. It reacts to the broadcast alright, but it doesn't tell me which of the two physical devices the action concerns. Is their a way to find out? Bluetooth.getName() is not allowed because it's not a static class.
if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
}
or 2) I listen for both actions for both devices.
if (myPinkHeadset .ACTION_ACL_CONNECTED.equals(action)) {
Log.v(TAG, "Connected to myPinkHeadset ");
}
else if (myPinkHeadset .ACTION_ACL_DISCONNECTED.equals(action)) {
Log.v(TAG, "Disconnected from myPinkHeadset ");
}
else if (myPcBluetoothDongle .ACTION_ACL_CONNECTED.equals(action)) {
Log.v(TAG, "Connected to myPcBluetoothDongle ");
}
else if (myPcBluetoothDongle .ACTION_ACL_DISCONNECTED.equals(action)) {
Log.v(TAG, "Disconnected from myPcBluetoothDongle ");
But then it logs that it connects with myPinkHeadset even if it is myPvBluetoothDongle I activate physically. It always goes for the one which comes first of the if tests. It cares only about the action itself, not about which object it concerns.
I saw that EXTRA_DEVICE is "Used as a Parcelable BluetoothDevice extra field in every intent broadcast by this class." But it only returns null to me:
String extra = intent.getStringExtra(BluetoothDevice.EXTRA_DEVICE);

This gives the device connected to:
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
As a newbie, I misunderstood the parcelable concept. EXTRA_DEVICE is a String, but it's just a tag for the object. So there's no need to register or listen to individual instances of BluetoothDevice. When an action is broadcasted, the intent will tell which physical device caused it. (Can I +1 myself for this :-D)

intentFilter.addAction(myPinkHeadset.ACTION_ACL_CONNECTED);
intentFilter.addAction(myPcBluetoothDongle.ACTION_ACL_CONNECTED);
and
intentFilter.addAction(myPinkHeadset.ACTION_ACL_DISCONNECTED);
intentFilter.addAction(myPcBluetoothDongle.ACTION_ACL_DISCONNECTED);
are the same value. It's static value.
BluetoothDevice.ACTION_ACL_CONNECTED and BluetoothDeviceACTION_ACL_DISCONNECTED
private void register() {
context.registerReceiver(bluetoothBroadCast, new IntentFilter(BluetoothDevice.ACTION_ACL_DISCONNECTED));
context.registerReceiver(bluetoothBroadCast, new IntentFilter(BluetoothDevice.ACTION_ACL_CONNECTED ));
}
private final BroadcastReceiver bluetoothBroadCast = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
switch (action) {
case BluetoothDevice.ACTION_ACL_CONNECTED: {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if(device.getAddress().equals(myPinkHeadset.getAddress)) {
//Do what you want
}
break;
}
case BluetoothDevice.ACTION_ACL_DISCONNECTED: {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
break;
}
}
}
};
I hope this can help you