Develop Reference

How to know if my App is connected to a device using BLE in Flutter?.. when app is the beacon

So my android app is behaving as a beacon, means, it will be advertising and other BLE devices will be connecting to it. Well, this is how our project is working so please don't raise questions on this as why am i using my app as a beacon and not as a scanner. Anyways, It behaves as a beacon and starts advertising and now I want to know that if a device connected to it. I cant find a way how to do this.
Of course, I am using this flutter package. beacon_broadcast 0.3.0
This is my code.
void startAdvertising() {
BeaconBroadcast beaconBroadcast = BeaconBroadcast();
beaconBroadcast
.setUUID(advertisingUUID)
.setMajorId(1)
.setMinorId(100)
.start();
}

First, Flutter is just a UI toolkit and has no support for other system APIs such as Bluetooth.
You should therefore look what the official Android APIs offer in the first place. Usually when using BluetoothLeAdvertiser for advertising, one often also adds an instance of BluetoothGattServer in order to handle connections. If you have created a BluetoothGattServer using openGattServer, you will get a onConnectionStateChange callback whenever a device connects or disconnects. So that answers your question how an Android app can get notified when a device connects. You probably also want to use the same API to add a GATT service so that the other device can communicate with your app. Other alternatives is to use the GATT client API if it's the other device that has a GATT server, or you might want to use the L2CAP CoC API.
Note that if Bluetooth is turned off/disabled/restarted, your BluetoothGattServer object will automatically die and you need to recreate it. To get notified when this happens, use a state change intent receiver for BluetoothAdapter.ACTION_STATE_CHANGED as explained in this example https://stackoverflow.com/a/9694138/556495 to recreate your BluetoothGattServer (and advertiser) when state is changed to STATE_ON.
Now, since you want to use Flutter but Flutter uses Dart, you cannot directly consume the Android APIs. Instead you need to write a bridge/plugin, to bridge your Dart code and Java code. See https://docs.flutter.dev/development/platform-integration/platform-channels for a tutorial how to do this. If you're lucky, someone else might have already created such a package that does exactly what you want. Unfortunately, the beacon_broadcast package you found, only implements BluetoothLeAdvertiser and not BluetoothGattServer, as can be seen by the source code here: https://github.com/pszklarska/beacon_broadcast/tree/master/android/src/main/kotlin/pl/pszklarska/beaconbroadcast.

How to get the physical channel configuration of the cellphone via programming

I want to get the PCI of both primary serving cell and secondary serving cell in 5G NSA, but it seems that I cannot get what I want using getAllCellInfo(). It seems that I need to parse the physical channel configuration as below:
{{mConnectionStatus=PrimaryServing,...,mRat=LTE,...,mPhysicalCellId=123},
{mConnectionStatus=SecondaryServing,...,mRat=NR,...}
Does anyone know how to get the (real-time) configuration? Or can I get the PCIs in another way? Thanks very much!

About PhysicalChannelConfig
The only possible way how to obtain PhysicalChannelConfig is via TelephonyManager.registerTelephonyCallback method. You can for example pass an instance of TelephonyCallback.PhysicalChannelConfigListener and you'll start obtaining what you need.
Please note that permission Manifest.permission.READ_PRECISE_PHONE_STATE is required, so your app needs to be a system app of carrier-privileged app.
There were some attempts to adjust this protection level, current status can be seen here. But as of Android 12 there's no way how to get PhysicalChannelConfig if you are a regular developer.
About PCIs
You can sometimes get PCIs of serving LTE and NR NSA cells via getAllCellInfo() as you mentioned. Sometimes there's one instance of CellInfoNr with PCI is present. This behaviour is device-specific.
Generally speaking - Android does not provide any official API you request.

Linphone cant receive incoming call on some wifi network after some time

I used Linphone sdk to develop an android SIP phone, every thing is good but on some wifi network cant receive call and server return USER_NOT_REGISTERED error.
for example :
at first after registration:
User A and user B can make call to each other successfully.
after about ten minute, when user A make outgoing call to user B , server say user B in not registered and wise versa.
User A and B is registered because can hear server message.
server is asterisk.
I repeat this test with csipsimple and it work without problem.
my app now is complete and port it to csipsimple is not easy.
is there any way to fix it?

No, there are no even moderate complexity way fix it.
That is internal issues in registration on linphone. It is common and well-known at least 5 years, but linphone dev team not care much.
You can try fix linphone core, or just use sip ping(asterisk qualify= option) in attempt to not loose connection.

You can try the enableKeepAlive set to true after the creation of the core.
Core core;
core = Factory.instance().createCore(......);
core.enableKeepAlive(true);

Cannot set temperature interval on sensortag

I'm creating an android application that interfaces with the texas instruments sensortag. One of the things the app needs to do is be able to change the frequency in which the temperature is reported to the app. I am able to change it through the official TI app which is great, but I cannot seem to get it working in my app.
When viewing the official app (iOS, can't run the android one?), it shows the temperature GATT service, which contains 3 characteristics. When I inspect the characteristics discovered by my app however, it only seems to find two - the data, and the notifications. Not the interval. I have attempted to construct this characteristic myself and write it however it doesn't do anything - no error, no success, just nothing.
The steps I've taken are essentially:
bluetoothGatt.discoverServices();
...
services = bluetoothGatt.getServices();
...
BluetoothGattService service = bluetoothGatt.getService(serviceUUID);
System.out.println("Characteristic = " + service.getCharacteristic(SensorTagGatt.UUID_IRT_PERI));
The output yields null. Is there something obvious I'm missing or that I should be doing that I might not be?
EDIT:
I've installed another app onto the phone written by another developer, and using this to inspect the services and characteristics available shows that it too is unable to find it, so I'm assuming there is something wrong with the android service discovery? The official iOS app is working as expected, and showing all characteristics. Unfortunately, the official android app seems to be incompatible with the version 1.5 firmware and crashes when trying to connect but I assume it too will fail to find the characteristic.
Has anyone else run into this issue and if so been able to get around it?

Sending DTMF tones over the uplink in-call

I'm working on a project that requires my app to be able to send DTMF tones on the voice's uplink frequency during an active call.
My 2 conditions are:
We don't use a customized Android platform
We don't need to root the phone
I've spent several days doing my homework and am aware that in-call DTMF sending is not supported by the current SDK/standard APIs. However, by using the relevant classes in com.android.internal.telephony I am hoping to mimic how the native Phone app does this. I followed this site on how to use internal APIs for standard 3rd party apps.
I've also set myself up with the Android OS dev environment and am able to run the Phone app in debug mode on an emulator to figure its inner workings.
I tried various ways on a stock standard emulator but the errors I got were:
After trying to install a renamed app based on Phone.apk's source using the sharedUserId of android.uid.phone, I got:
Installation error: INSTALL_FAILED_SHARED_USER_INCOMPATIBLE
No doubt due to the fact I don't have the system cert to sign it.
After trying to write a custom app based on the relevant DTMF tone sending code from Phone.apk's source, I get the following error at setting up the PhoneFactory;
java.lang.SecurityException: Permission Denial: not allowed to send broadcast android.provider.Telephony.SPN_STRINGS_UPDATED.
No doubt due to the fact my app doesn't have the right permissions, although AndroidManifest.xml is setup with the same permissions as Phone.apk.
I'm at a loss as to what else I could try. Does anyone have any suggestions?
Thanks in advance,
Simon.

You've taken an interesting approach, and I commend your efforts. Unfortunately, there are some reserved internal privileges (evidently, such as SPN_STRINGS_UPDATED) that you aren't allowed to use as an app developer, which more or less breaks this approach. You could try removing the area of code causing this, but I'm fairly certain you will run into a blocking problem.
Hence, I'm afraid this is not possible at the moment. There's an open feature request on Android for sending DTMF tones over an existing phone call, but it has been dormant there for almost two years.
I understand that this doesn't resolve your problem, but take note that you can send DTMF tones directly after dialing a number:
Intent i = new Intent("android.intent.action.CALL",
Uri.parse("tel://" + number + "," + dtmfTones));

Simply put, you won't be able to do it without customizing at least the Phone app, which has to run as a system user in order to access the modem. In order to do this, you have to root your phone.
To meet your requirements the only possible solution is to enhance the android platform. We did just that, and already sent in our patches to the AOSP project:
https://android-review.googlesource.com/32820
https://android-review.googlesource.com/32821
We are currently waiting for the Google developers to review and accept our contribution. If you are interested, please let Google know on the various AOSP lists (android-contrib, android-platform). It will hopefully expedite the review.
Best Regards,
Gergely

You can't send DTMF tones during an active call, but you can send them when you "program" them when you initiate the call.
see the following post: https://stackoverflow.com/a/12986066/475472