I have found an issue while programming my application on an Android Device. I am trying to continuously gather data from a BLE sensor (Nordic Thingy). Everything runs smooth, but if I get to a point where the device disconnnects for a while (e.g. bad signal) the device can enter DOZE mode.
DOZE mode won't affect while there is an ongoing subscription to a BLE Characteristic and updates are being received. Is there any way to overcome the DOZE-Standby mode programmatically so that my device keeps searching for the device even if it is disconnected?
This is a key task for my project and I have't find any way for dealing with this behaviour yet.
I manage to solve this issue by implementing a Foreground Service which is in charge of supervising the connection and keeps the CPU alive preventing from entering DOZE mode.
Related
The situation:
I'm developing an android app for some hardware that has a BlueGiga WT12 bluetooth modem. The hardware device sends 56 byte packets at around 240hz. I'm testing on a Samsung S5 and S8. A fully functional app has already been created for IOS and PC so we know the hardware device works.
I use a separate thread to read in the data and then dispatch it to the main thread.
Issue:
The issue I'm having is when I send the command to the device telling it to start streaming, it starts to stream but very shortly after I start receiving packets at a very slow rate 10-60hz.
After some examination I realized that the device was experiencing a bufferoverflow.
After talking to our hardware guy he said the only real thing that could cause that is something on the phone side not reading fast enough, resulting in the hardware device not wanting to send more packets because it thinks the phone can't receive anymore and then the buffer overflows on the hardware device.
The WT12 has flow control enabled so maybe this is an issue with Android not giving a clear-to-send signal to the WT12. But to my knowledge we don't have access to all of the flow control stuff.
What I've tried:
My first line of attack was to simply remove any code that I thought was slowing down the reads but that seemed to have no effect.
I also tried basically every bluetooth serial terminal app I could get my hands on, all with the same result.
So then I questioned if it was some weird problem relating to the hardware device but after using pc based (bluetooth) serial terminals I had no issues at all on the pc.
The hardware device can also operate over USB as opposed to bluetooth so I tried reading the data from it exactly the same as I had with the bluetooth connection but over USB. Using the USB serial connection I had no issues at all.
My thoughts:
So this leads me to believe the problem must be with the bluetooth modem on the phone side. I was thinking maybe it was a flow control issue as we have flow control enabled on the WT12. Maybe android isn't sending a clear to receive signal?
The problem is to my knowledge the flow control is implemented in the bluetooth stack and we as developers have no control over it if I'm not mistaken?
Other then flow control I don't really have much idea what could be causing the hardware device to not want to send me data.
I've just now been experiencing the same issues with flow control. Then I see that in case of RN4678 BT module, that it's best to disable the flow in the MCU FW and pull the cts pin low on the module. That worked for us.
I have app that is droping BLE connection in background after 10 minutes.
Everything works fine when app is connected to Debbuger if the device is locked while the app is in foreground the connection will be dropped after 10 minutes, but if we disconnect it and lock the device while the app is in Foreground , the connection is not dropped after timeout.
Are there some restrictions to Background execution when device is locked? Why does it work when connected to Debbuger?
Use Service in Foreground to create strong connection, it's the best option.
But even Foreground service doesn't help if Battery saving mode enabled, or another battery optimization modes.
Yes, debugger prevent app from being killed by system, actually not debugger but ADB connection. Sometimes test your application without USB plugged.
Also use PowerManager.WakeLock in service, it helps.
What I have studied on stackoverflow and Android documentation.
Finally I've concluded this:
There is no way to create a background service for continuous tasks. If I really want a service I should start a foreground service and user continuously sees a persistent notification "App is running". There is no way to hide this notification. It is intentionally added by Google.
Yes there are other options like WorkManager and JobScheduler but they do work periodically not continuously.
What I do want is to build an instant messaging app which continuously connects to the server using xmpp or sockets. But it requires a continuous connection but I don’t want to use a foreground service because it shows an irritating notification to the user "App is running".
Question 1: How does Whatsapp and other instant messaging app continuously connect to the server but not show a persistent notification ? How do they achieve this ?
Question 2: If Whatsapp use FCM for notifications then it will also work in those mobile which do not have playservices installed, so how does Whatsapp notification mechanism works ?
Starting with Android 6.0 (API level 23), Android introduces two power-saving features that extend battery life for users: DOZE and APP STANDBY. These two features enforce many restrictions on your background processing while the phone is in Doze mode. You should read about Doze and app standby in the following link
https://developer.android.com/training/monitoring-device-state/doze-standby
Now, about your use case is that you want to receive the messages and incoming calls even when the app is not running. For this use case, Android announced High Priority FCM messages in GoogleIO2016. They are high priority Push message which grant the application temporary wakelock and network access, independent of Device's Doze state or if the app happens to be in the app standby. This allows the application to react to the message and notify the user in whatever way it wants about the instant message or incoming call.
I don't know exactly how WhatsApp does that unless I look at their code but you can handle your use case using FCM High Priority Messages.
For more about your use case, follow the below link ofGoogleIO2016 Video from 08:30m to 10:30m
https://www.youtube.com/watch?v=VC2Hlb22mZM&t=505s
and read about this use case on the first link in this answer.
I need to have control over some admin features of android device.
Is it possible to acquire control over hardware not specified in android.app.admin.DevicePolicyManager like disabling access to microphone?
Also it will be good to find ability to track network connections or attempts to use network adapters by apps.
Maybe some command for root console or other way exist - how I can search for?
As far as i know there is no way to block any other hardware except camera with device manager. I believe that if your app takes control of microphone it will be unavailable to other apps, but i am not sure. Note that from android 8.0 no app is allowed to take control of microphone while in background.
About tracking network activity you could open vpn to monitor all packets that are sent and received.
Please keep in mind that i am not familiar with root methods so you should do some more research on this.
I am running a multi thread application on android and adobe air, in native android 2 bluetooth sockets are set up and a couple of server threads for the air app to communicate with the bluetooth sockets of native android. It's basically socket programming and it all works on one device I used to programme it.
The device i used to develop this app was slow, i therefore got myself another tablet to test (android vega) and it is very fast at communicating my bluetooth data as it has 2.1edr version.
The problem is with the Advent Vega tablet the bluetooth streams just disconnect for no apparent reason intermittently and in the adb log window i just get trying to connect to device all of a sudden when the disconnect occurs, i have no mention of the crash anywhere in the log, this happens to both bluetooth connected threads at the same time so it must be something to do with the bluetooth radio im suspecting. The other tablet device runs the app fine but slower (no disconnects). I have even installed a custom 3.0 rom on the vega to see if it was a os problem but the disconnect problem persisted on 3.0 as well.
Due to the fact there is no mention of this in the adb log i am just basically staring at a screen with no idea of why it disconnects for 2 days now!! The only way to get the app to run again after this disconnection occurs is to restart the bluetooth on the device but this disconnect occurs again eventually when next run. It seems to improve the amount of time it stays alive tansferring data when the app is first run afater a re boot.
I have gone through all code of the run() and stopping() of each thread and it seems to exit gracefully, i close the bluetooth sockets only, it seems from research no need to close the bluetooth input and output but i have also tried that approach to closing.
Can anyone offer suggestions as to why both bluetooth read/write loops would just stop all of a sudden and disconnect? Seemingly effecting the adb log as well as it just says trying to connect...
Or any suggestions as to how to better debug when this occurs?
Or even what somebody else would do in this situation.
Hope someone can help, i have a great phone remote app for the android tablet owner community and it hinges on this final issue which i have been stuck on for 2 days.
I had problems with disconnects, and implemented a keepalive by sending a ping request and a ping ack.
This worked fine for me...