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NFC is on, but adapter is not enabled

I am working on android project, where NFC is used as a communication. I am facing a weird problem, when mobile device has a NFC, it is enabled, but it is not working on some devices (adapter is not enabled when debugging). I am writing logs and it prints, NFC on, adapter disabled.
For example: HTC One m9(os 7.0). Also happens with OnePlus One(os 9)! But again, it works on other devices.
Did you experience the same issue?
Here is some code:
object NfcUtil {
fun getNfcAdapter(c: Context): NfcAdapter? {
val manager = c.getSystemService(Context.NFC_SERVICE) as NfcManager
return manager.defaultAdapter
}
fun doesSupportHce(c: Context): Boolean {
return c.packageManager.hasSystemFeature(PackageManager.FEATURE_NFC_HOST_CARD_EMULATION)
}
}
val adapter = NfcUtil.getNfcAdapter(this)
if (adapter != null && NfcUtil.doesSupportHce(this)) {
if (adapter.isEnabled) {
tvNfcOff.extHide()
} else {
tvNfcOff.extShow()
}
}

I think that if NFC is supported and enabled but the adapter is disabled (https://developer.android.com/reference/android/nfc/NfcAdapter#isEnabled()) I'll follow the guidelines and redirects the user to the settings screen with the intent mentioned in the documentation.
If the user come back few times you could monitor it and show a different message instead of redirecting to settings, something like: NFC is not working properly on your device. I'd check if you have lots of users using those devices, if yes, I will try to research more on the Operating System and Device having this issue.
And later on I will just try to debug it with that Device and that specific Operating System that is having this kind of issue. I'll try to see if other apps using NFC has same issues or they work fine, and by work fine I mean that the communication happens not that other apps dont show any warning/error popup message.
And if I found out its an issue in a specific OS Version, also with other apps, I'll just try to inform the users and get an update on which version the issue have been fixed. Otherwise if other apps can make a successful NFC communication in that device/OS that is not working for me, I'll just dig deeper.
For now I can say there is nothing wrong in your implementation and looks good.
It might be an issue with the current OS or if you have any Custom ROM that might not fully support or have a functional NFC driver.

Two additional bits of info that might be useful
1) Use a Broadcaster receiver to get notified when the NFC state changes, because using the quick settings pull down does not pause your app, therefore retesting nfc status in onResume does not work (a user changing via the full settings app will pause you App, though)
Example of how to do it in Java
#Override
protected void onCreate(Bundle savedInstanceState) {
// All normal onCreate Stuff
// Listen to NFC setting changes
this.registerReceiver(mReceiver, filter);
}
// Listen for NFC being turned on while in the App
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (action.equals(NfcAdapter.ACTION_ADAPTER_STATE_CHANGED)) {
final int state = intent.getIntExtra(NfcAdapter.EXTRA_ADAPTER_STATE,
NfcAdapter.STATE_OFF);
switch (state) {
case NfcAdapter.STATE_OFF:
// Tell the user to turn NFC on if App requires it
break;
case NfcAdapter.STATE_TURNING_OFF:
break;
case NfcAdapter.STATE_ON:
// Do something with this to enable NFC listening
break;
case NfcAdapter.STATE_TURNING_ON:
break;
}
}
}
};
2) Don't assume that the device has a NFC settings page, if your app works with and without NFC, if the adapter is null don't assume you can start an Intent to the NFC settings page as suggested by #denis_lor as this will cause a crash if the OS does not have a NFC adapter to turn on.

Is there possibility to "Auto-start" application when users become inactive?

I have to create an app, which detects user inactivity, and then start activity which displays some videos with WebView, and then when displaying with WebView is finished, it has to play videos from SDCard. I've already handled part with WebView and SDCard (with JavaScriptInterface etc.)
This application has to work with API 19 all the way to the newest one.
The question is - Is there a possibility to detect if user is inactive and start my application, or keep the app running in background, and then start activity in the foreground after the user becomes inactive for certain time?
I'm not trying to play ads, when user is not looking at his screen. Application is for my client, who have stores with all kind of electrical equipments, including smartphones. The goal is to play video presentations with hardware details specific for each smartphone (informations about processor, ram, camera, screen etc.).
In short: I have to make an app which is similar to "Demo Apps" created for example by Samsung (playing some kind of presentations on screen).
So far I've read and tested things like:
1) BroadcastReceiver with combination of ACTION_SCREEN_OFF / ACTION_SCREEN_ON events.
Receiver works properly, I can detect this event and then start activity, but... The screen is already off so i can't see the displayed activity - it's visible running in the foreground after unlocking the phone. Is there a way to unlock the phone when the event is received?
That's my code so far.
EventReceiver Class:
class EventReceiver: BroadcastReceiver() {
override fun onReceive(context: Context, intent: Intent) {
StringBuilder().apply {
append("Action: ${intent.action}\n")
append("URI: ${intent.toUri(Intent.URI_INTENT_SCHEME)}\n")
toString().also { log ->
Log.d(TAG, log)
Toast.makeText(context, log, Toast.LENGTH_LONG).show()
}
}
if (intent.action == Intent.ACTION_SCREEN_OFF) {
val i = Intent(context, MainActivity::class.java)
context.startActivity(i)
}
}
}
MainActivity Class:
val br : BroadcastReceiver = EventReceiver()
val filter = IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION).apply {
addAction(Intent.ACTION_SCREEN_OFF)
addAction(Intent.ACTION_SCREEN_ON)
addAction(Intent.ACTION_BOOT_COMPLETED)
}
2) Foreground Services - I read that this is a great way to make some asyc stuff in the background and show notifications to user. Is there a way to start the activity with it?
3) Job Scheduler
4) Daydream / Dream Service - it actually works great with almost every API and manufacturer, but.. there's no way to set the app as Screen Saver on Huawei/Honor smartphones, at least from phone settings, I've read that this is possible with ADB etc. but this is not an option that I can use here.
It seems that none of these fullfill my expectations.

BLE Scan not working in Background with Scanfilters in android pie?

I am using blescan with scanfilters to detect beacons it's working very fine in foreground and background up to oreo version but when it comes to android pie it's not able to send pending broadcast in background.
ScanSettings settings = (new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)).build();
final List<ScanFilter> scanFilters = new ArrayList<>();
scanFilters.add(getScanFilter());
BluetoothAdapter bluetoothAdapter;
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
bluetoothAdapter = bluetoothManager.getAdapter();
Intent intent = new Intent(this.getApplicationContext(), MyBroadcastReceiver.class);
intent.putExtra("o-scan", true);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
bluetoothAdapter.getBluetoothLeScanner().startScan(scanFilters, settings, pendingIntent);
public class MyBroadcastReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
int bleCallbackType = intent.getIntExtra(BluetoothLeScanner.EXTRA_CALLBACK_TYPE, -1);
if (bleCallbackType != -1) {
Log.d(TAG, "Passive background scan callback type: "+bleCallbackType);
ArrayList<ScanResult> scanResults = intent.getParcelableArrayListExtra(
BluetoothLeScanner.EXTRA_LIST_SCAN_RESULT);
// Do something with your ScanResult list here.
// These contain the data of your matching BLE advertising packets
}
}
}

Android 9 introduces several behavior changes, such as limiting background apps' access to device sensors and Wi-Fi scans.
These changes affect all apps running on Android 9, regardless of target SDK version.
Sensors that use the continuous reporting mode, such as accelerometers and gyroscopes, don't receive events.
Android 9 Limited access to sensors in background:
Android 9 limits the ability for background apps to access user input and sensor data. If your app is running in the background on a device running Android 9, the system applies the following restrictions to your app:
Sensors that use the continuous reporting mode, such as accelerometers and gyroscopes, don't receive events.
Sensors that use the on-change or one-shot reporting modes don't receive events.
Solution:
If your app needs to detect sensor events on devices running Android 9 while the app is in the background, use a foreground service.

I an example test Android app using Oreo (API 26) and the the code above (slightly modified) to detect beacons. I am using the Pixel 3 XL (with Pie).
I think that the hard part about this is to know for sure if the code in onRecieve() in MyBroadcastReceiver is actually being run upon detection of a beacon when the device is running on battery only (disconnected from Android-studio and Logcat (USB)).
Using Volley (com.android.volley) to submit a HTTP request to a local http server, I was able to demonstrate that it works as documented - ie. I am able to receive the http request when beacon(s) are detected. However, Volley only sends these these requests when Android is awake or when it periodically wakes up and connects to the network - which in my simple tests was about every 15 minutes (plus some variation), but I did get all the beacon ScanResults on my HTTP server, just in delayed up to 15 minutes. I was even able to remove the app from the list of running apps (you know; swiping up to remove the app) and still see that the onRecieve() in MyBroadcastReceiver was receiving BLE ScanResults.
How do you know that the onRecieve() in MyBroadcastReceiver is being killed? I am very interested to know how you know this.

How force the app to opt out of battery saver mode when the service is ON?

The expected behavior is that the app will be running all the time when it's in ON state. Some phones put the app in background mode when the app is not active for some time. I want the app to be running all the time even its in standby mode(standby mode means when we press the home button the app will go to background. and it will run for some time).
I found following code and I tried that
PowerManager powerManager = (PowerManager) getApplicationContext().getSystemService(POWER_SERVICE);
String packageName = "org.traccar.client";
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
Intent i = new Intent();
if (!powerManager.isIgnoringBatteryOptimizations(packageName)) {
i.setAction(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
i.setData(Uri.parse("package:" + packageName));
startActivity(i);
}
else{
i.setAction(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
i.setData(Uri.parse("package:" + packageName));
startActivity(i);
}
}
Even after working with the code the default state is Battery Saver(recommended)
I want the app in No Restriction mode once the app is opened, any solution for this?

The code you use is for battery optimization. Settings-->Batery-->Three Dots Menu Item (...)--->Battery Optimization-->(Choose an app from list)--->Optimize/ Don't optimize.
By choosing Don't optimize you are essentially bypassing Doze, not app standby.
Also be advised that doing this programmatically as you do may result in Google taking your app off the store. It is safer to do it manually following the path i described above.
More on Doze and App Standby here

Turn screen off programmatically

I'm working in an app that needs to to do any of this actions:
Lock the device
Put the device in sleep mode
Turn off the screen
How can I achieve this?
Found this option, but it requires the proximity sensor to be in "near" state to turn off the screen:
mWakeLock = mPowerManager.newWakeLock(PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK, "tag");
mWakeLock.acquire();
Thanks

If your app is a device admin you can lock the screen with DevicePolicyManager.lockNow()
You can use this snippet (after setting the Device Admin part):
DevicePolicyManager manager = ((DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE));
manager.lockNow();