I have been trying to get the Android developers bluetooth example code
( http://developer.android.com/guide/topics/connectivity/bluetooth.html )
to work reliably but unfortunately it keeps crashing after the socket closes 50 or even up to 1000 times.
A SPP BT module (HC-06) is used that is shut down every minute to reproduce the problem.
The weird thing is that when it crashes the pairing is lost and you have to re-enter the pin number. I use a timer to reconnect after the socket closes. Also tried without a timer and used a "new ConnectThread(device).start()" in the IOException handler.
Posting the code is not much use because I use the same code as the Android developers example.
Help would be greatly appreciated.
Android version: 4.1.1 and 4.2.2
Related
I am working on a part of an indoor localization project. I need my Flutter application scan and get Mac addresses and RSSI values of Wifi and Bluetooth devices. I am using flutter_blue for bluetooth scans and wifi_scan for Wifi scans. The application works well while in the foreground but scans are failing when the application is in background.
What I have tried so far:
Tried to change Bluetooth scan mode from ScanMode.lowLatency to ScanMode.lowPower and ScanMode.opportunistic for the startScan() method for flutter_blue.
flutter_background. I managed to do some tasks in background but wifi and bluetooth did not work.
flutter_background_service the same situation
flutter_foreground_plugin the same situation
flutter_foreground_task the same situation
workmanager did not try it because it says it can trigger the bg operation per every 15 minutes but I am scanning per every 6 seconds.
Is there any way to achieve this? Aren't there any package with the option backgroundMode: true? I don't know the natives. Don't know Kotlin too.
According to the Android Developer documentation, ScanMode.lowPower is the only possible mode for background scanning. You also need to request location access for the background (documentation here and here).
Consider switching to Flutter Blue Plus instead of Flutter Blue; Flutter Blue Plus is the currently-maintained version. This pull request on GitHub shows that Flutter Blue cannot run in the background. The pull request has never been merged.
After a lot of things have been tried, I just tried to get GPS location too.
Used this package: location
And execute location.enableBackgroundMode(enable: true) as it is stated in readme, then my wifi and bluetooth scans starts working in background too.
It's Ridicoulus
I have an Asus P00A tablet (Android 7.0, API24) on which the BLE stops after some hours. (This affects any BLE app, not just my app using Android Beacon Library). Apps start working again if I manually switch off BLE then switch it back on.
The BluetoothMedic auto-fix system did not work for my tablet. It runs every 15 minutes but does not find a fault and so does not "power cycle" the Bluetooth. However, I hacked the BluetoothMedic class, adding this:
public void cycleBluetooth(Context context) {...}
and attached this to a button. I find this will restore BLE functionality. So I wondered what would happen if I unconditionally reset the BLE every 15 minutes. I added:
public static final int ALWAYS_RESET = 4;
and then call medic.enablePeriodicTests(context, BluetoothMedic.ALWAYS_RESET);
and add code inside BluetoothTestJob.onStartJob() which then calls BluetoothMedic.cycleBluetooth(). This behaves as expected and so far my app has run perfectly for 18 hours.
I am interested in any advice, such as:
1 Are there any tests other than the two in BluetoothMedic that I can run to detect that my tablet's Bluetooth has stopped? (I am happy to experiment).
2 Any comments on the hack I describe above? Should it be OK to unconditionally reset the Bluetooth every 15 minutes?
3 If the Bluetooth is reset ("power cycled") then is the rest of the Android Bluetooth Library OK with this? That is, will it carry on with monitoring and ranging that has been previously set up, or does the application code need to set take any action to get things going again? Note that this would apply to resets by the existing enablePowerCycleOnFailures() code as well as my ALWAYS_RESET hack above. (Maybe there are some crashes that could happen if the power cycling came at the wrong time?).
4 Could I suggest adding a callback so the application can learn if the Bluetooth has been cycled? Perhaps as a parameter to enablePowerCycleOnFailures()
5 I understand that background activities can be stopped by the OS, especially with Android 8. Would this also affect the regular 15 minute tests set up by enablePeriodicTests()?
The Android Beacon LIbrary's BluetoothMedic, as currently built, relies on the operating system's error code returned by a scan failure (or an advertising failure) to decide if the bluetooth stack is in a bad state warranting a power cycle.
For scans, if the onScanFailed callback is called with an error code of SCAN_FAILED_APPLICATION_REGISTRATION_FAILED which has the value of 2, the module considers it worthy of a power cycle..
For advertisements, if the onStartFailed callback is called with an error code of ADVERTISE_FAILED_INTERNAL_ERROR which has a value of 4, the module considers it worth of a power cycle..
These values were determined via experimentation, witnessing that on some devices, once an error callback is called with these values, bluetooth on the device would not work again without turning it off and back on. You can see the discussion of this in this thread.
You may want to see if there are other error codes on the Asus P00A that indicate a problem worthy of cycling bluetooth. To do this, wait for a failure, and see if attempts to start scanning call the onScanFailed callback with a distinct error code. If such error codes exist, this would be a better solution than cycling power to bluetooth regularly, as cycling power to bluetooth does break BLE GATT connections and the operation of bluetooth classic functions like speakers. The Android Beacon Library itself recovers from these power cycles just fine, although it will obviously not detect beacons until bluetooth is back on.
Because the BluetoothMedic uses the Android Job Scheduler for periodic tests, it is not affected by background limitations on Android 8+.
If you are interested in augmenting these functions in the library, please feel free to open an issue in the Github repo, and issue a Pull Request if you have code to share.
I am facing quite a peculiar problem.
I am programming on Android to get a reading from a BLE Blood pressure monitor(A&D UA 651). I am able to get the reading from the device on certain devices(galaxy S6, Note 2, Droid Turbo), but on other devices(like the Oneplus One, HTC Desire 810) etc, I am able to connect to the BP monitor, but cannot get a reading from it.
I followed the tutorial posted by Android here.
Write now, I am using setCharacteristicNotification() to alert me of any changes in characteristics. I am also writing the correct descriptor using:
descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);`
Here's the kicker. I've noticed that on the devices where I am not alerted of a change in the characteristic value, if I put a breakpoint inside the callback
onDescriptorWrite(), I am able to get the reading.
The status value in the callback is always 0 (irrespective of whether I can read the value on the characteristic or not.)
This lead me to thinking that I should induce a delay in this callback, but this seldom works.
If anyone has faced this issue before, please let me know. I've been stuck on this issue for quite some time now.
Thanks!
when opening a bluetooth rfcomm socket via the UUID method ( the other method ( using reflection ) in here http://code.google.com/p/android/issues/detail?id=5427 ) - I sometimes get the following error ( after successfull connections ) and the socket is not opened:
E/BluetoothService(21847): Received ACTION_UPDATE_SERVICE_CACHE00:0B:CE:01:2E:00
D/BluetoothService(21847): updateDeviceServiceChannelCache(00:0B:CE:01:2E:00)
D/BluetoothService(21847): Cleaning up failed UUID channel lookup: 00:0B:CE:01:2E:00 00001101-0000-1000-8000-00805f9b34fb
had no luck with google on this one - has anyone here a clue whats going on and how to prevent that?
Update:
for people running into the same problem - possible solutions:
advice the users to reboot the device if we run into that state (
very bad UX )
use the reflection method ( dirty but works most of the time )
I am still open for new Ideas ;-)
I stick to #2 at the moment - but waiting for a better solution.
It seems that the message is the consequence, not the reason. If a serial port emulation service is not found on device the connection will obviously fail.
Update
After reviewing code everything seems ok. So my questions are: Do the random errors occur with same device o with different devices? If the occur with different devices, the devices might have not registered the SerialPort service. Is device previously paired? In case of the error ocurring randomly with same device? Are you using the connection class concurrently? You have not protected the methods against concurrent access. You have not protected either against succesive connects. If you try to read/close a stream after a second connect it will fail (the socket object has changed).
It seems ok. The random error occurs with same device? If this is the case, are you using concurrent use of that class? In first case
I'm working on a research project which involves Bluetooth and the Android OS. I need to make Bluetooth discoverable indefinitely in order for the project to continue.
The Problem:
Android limits discoverability to 300 seconds.
I cannot ask the user every 300 seconds to turn discoverability back on as my application is designed to run in the background without disturbing the user.
As far as I am aware, there is no way to increase the time though Android's GUI. Some sources have called this a safety feature, others have called this a bug. There may be a bit of truth in both...
What I'm Trying / Have Tried:
I'm trying to edit a stable release of cyanogenmod to turn the discoverability timer off (it's possible; there's a configuration file that needs to have a single number changed). This isn't working because I'm having verification problems with the resulting package.
During the past week, I downloaded the cyanogenmod source code, changed a relevant class in the hope that it would make Bluetooth discoverable indefinitely, and tried to recompile. This did not work because (a) the repo is frequently changed, leading to an unstable code base which fails to compile (OR, it could be that I'm using it incorrectly; just because it looked like it was the code's fault in many instances doesn't mean I should blame it for all the problems I encountered!) and (b) the repo decides to periodically "ignore" me (but not always, as I have gotten the code base before!), replying to my synchronization/connection attempts with:
fatal: The remote end hung up unexpectedly
As you might imagine, the above two issues are problematic and very frustrating to deal with.
More Info:
I'm running Android 2.1 via cyanogenmod (v5 I believe). This means the phone is also rooted.
I have a developer phone, which means that the bootloader is unlocked.
My phone is an HTC Magic (32B).
The Big Question:
How can I make Bluetooth indefinitely discoverable on Android?
See the following link:
http://developer.android.com/guide/topics/wireless/bluetooth.html#ConnectingDevices
Specifically, the last sentence in the paragraph below:
Enabling discoverability
If you would like to make the local device discoverable to other devices, call startActivityForResult(Intent, int) with the ACTION_REQUEST_DISCOVERABLE action Intent. This will issue a request to enable discoverable mode through the system settings (without stopping your application). By default, the device will become discoverable for 120 seconds. You can define a different duration by adding the EXTRA_DISCOVERABLE_DURATION Intent extra. The maximum duration an app can set is 3600 seconds, and a value of 0 means the device is always discoverable.
So, this should work:
Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 0);
startActivity(discoverableIntent);
If you check out the BluetoothAdapter class
you will find the hidden method:
public void setDiscoverableTimeout(int timeout)
Now you only have to find out how to use it. You have to do a method invocation to do so.