Develop Reference

Flutter app keeps disconnecting from firestore after brief time

I'm currently working on an application that causes devices connected to firestore to vibrate on cue. Currently it works fine, but after ~5+ minutes of a connected device/app being put to sleep, there is no response. Currently I have it so connected devices are given a bool field which has a listener to vibrate the device when the bool is true. I was thinking of sending a push notification to try and force the device to vibrate, but that's if there's no solution. Is there anyway to force the device to remain listening for firestore changes for an extended period of time? (listening in the background)?

This is expected behavior and not anything Firebase/Firestore controls. To conserve battery life, Android closes connections from applications if they haven't been actively used in a while.
For this reason you can't expect to keep receiving updates from Firestore (or any other such mechanism) if the app is backgrounded or if the phone is put to sleep.
The common solution for this is indeed to (also) send updates through FCM, which is treated differently by Android's power management feature.

Android background service with network connection

Goal
Create a long-running background service with a network connection, similar to Zello app.
Problem
Starting with API level 26 (Oreo), there're tight restrictions on background services and their network activity.
Looking at the Zello app which has a constantly running background service which is able to accept audio and text messages even if the device is sleeping, I wonder how they achieved that?
Their service is not running on the foreground. Also, it doesn't look like they use push messages for that, since the app works quite stable in conditions where there's a problem with push messages reception (e.g. low-end Xiaomi phones).
Any ideas would be appreciated.

From what I gathered these apps use the Firebase Cloud messaging service:
https://firebase.google.com/docs/cloud-messaging/
The Firebase Service is embedded in the Android system and maintains a constant network connection to the firebase server. The apps then contact the firebase server which in turn to notifies the destination device.
Advantages:
The Android system is responsible of keeping the server connection alive and running
The network load is minimized because one connection is used for all apps using the firebase service.
Disadvantages:
All data is sent through the firebase server and is therefore (in theory) directly accessible by Google
Depedning on how many devices use your app, you need to pay for the service.
A similar question asked might be helpful in tackling the problem too:
How does push notification technology work on Android?

These apps don't have long-running services with constant network connections. They use push notifications. When there is a new message for a user, the server sends a push notification to wake the device up.

Push message cannot start service at once

Context
We are developing an android app that is supposed to do the following:
the user installs the app, registers and closes the app
once or twice a year an admin sends a Firebase data message with priority high to the user containing a geo fence
the FCM message starts a JobService that locates where the phone is
if the phone is inside the given area an Activity is started and user interaction starts
if the phone is outside the area the service is stopped and the user is never disturbed
I developed the app based on the Firebase push example found here
The problem
The application works fine on my older phones but on my new test phone (android 8.1.0, LineageOS 15.1) we have a problem when the phone is in sleep mode. In this case the FCM message arrives instantly but the service is first started once the phone is unlocked. So the message is stuck between 2. and 3.
We need the app to respond at once - not when the user decides to use his phone 2 hours later.
I assume the problem is due to the Doze mode introduced with android 6. I tried to solve it by adding the app to the whitelist in settings->battery->battery optimization but this did not solve the problem.
Questions
Is it Doze mode that delays my app between 2. and 3.? If so why is it not solved when the app is in the whitelist?
Is there any other way to start the location service at once? This post suggests that a foreground service can do it but this requires that a notification is shown which breaks with 5.
Is there another way to start my service at once besides whitelist and foreground service?

Yes! you are right this may be due to the Doze and App Standby features introduced in API 23 Marshmallow.
As mentioned in the documentation, the system do ignore wakelocks and system doesn't allow JobScheduler to run, which effectively prevents your app from running the Job.
An easy and effective workaround would be to run Location detecting routine inside a normal background service and start it using startService() when you receive FCM push.
Note that you might still need to white-list your app because as mentioned in another post here, only a whitelisted app can use the network and hold partial wake locks.

Is it Doze mode that delays my app between 2. and 3.?
From the documentation Doze mode affect Network access and blocks JobScheduler.
If so why is it not solved when the app is in the whitelist?
Also from the documentation: An app that is whitelisted can use the network and hold partial wake locks during Doze and App Standby. However, other restrictions still apply to the whitelisted app, just as they do to other apps.
So the blocking of JobScheduler still applies.
Is there any other way to start the location service at once? This
post suggests that a foreground service can do it but this requires
that a notification is shown which breaks with 5.
Ignore Battery Optimizations (for Internet access) in combination with an AlarmManager with setAndAllowWhileIdle() or setExactAndAllowWhileIdle() should work.
Be careful with Ignore Battery Optimizations
Google Play policies prohibit apps from requesting direct exemption from Power Management features in Android 6.0+ (Doze and App Standby) unless the core function of the app is adversely affected.
I think an important question here is: Do you really need to execute the JobScheduler immediately.
If a user leaves a device unplugged and stationary for a period of time, with the screen off, the device enters Doze mode.
If the device is in Doze mode, it means the user is not using it.
if the phone is inside the given area an Activity is started and user interaction starts
This is the step Doze blocks
We need the app to respond at once - not when the user decides to use his phone 2 hours later.
If the device is in Doze it means the user is not interacting with it. Even if you show the Activity the user is not using the phone, he will see it when he starts using it 2 hours later :)

I still didn't try that,
but you might use a WakefulBroadcastReceiver:
https://developer.android.com/training/scheduling/wakelock.html
https://developer.android.com/reference/android/support/v4/content/WakefulBroadcastReceiver.html
According with this links, you should declare your receiver as:
public class YourReceiver extends WakefulBroadcastReceiver {
Probably your receiver is already a WakefulBroadcastReceiver because notifications are showing..
In the receiver, you start the service (your service has to be an IntentService) using:
startWakefulService(context, your service);
Finally, remember to release the wake lock in the service:
#Override
protected void onHandleIntent(Intent intent) {
<Your_broadcast_receiver_class>.completeWakefulIntent(intent);
}
I hope it helped

Dealing with Android-Doze mode on my BLE monitoring app while user's sleeping

I made the device which monitors person's health in sleep time and it connects to a smartphone via BLE.
It's working great with the iOS app.
But since Doze mode came on Android world.
It's really hard to deal with it because my device is working in his sleep time.
The main feature is that it detects particular danger and notify to the user while he is sleeping with the device. I need a network connection when it occurs.
Many articles tell me that I can use a network even in the doze mode if my app is in the whitelist. But it does not seem true after I tested Doze mode.
Am I right?
I can ensure that I can find my app in the lists, when I fire
adb shell dumpsys deviceidle
What is the best approach that I can take to make my app working correctly?
foreground services
alarm manager with SetExactAndAllowWhileIdle.
GCM (it means push, right?)
anything else
Any tips will help me.
Thanks.
Edit
Unfortunately, I tested with using GCM but it only wakes my app in short time. It means I have to send GCM as many as I want to keep it awake. I don't think I can use it.

Many articles tell me that I can use a network even in the doze mode if my app is in the whitelist. But it does not seem true after I tested Doze mode. Am I right?
You are not right. One of the restrictions of doze that are lifted when your app is on the whitelist, is the ability to use the network when doze is active.
An app that is whitelisted can use the network and hold partial wake locks during Doze and App Standby. However, other restrictions still apply to the whitelisted app, just as they do to other apps. For example, the whitelisted app’s jobs and syncs are deferred (on API level 23 and below), and its regular AlarmManager alarms do not fire.
From here.
In other words: you should be able to use the network in doze if you are on the whitelist.
What is the best approach that I can take to make my app working correctly?
Considering your app is a health monitor and thus should be able to do its work constantly or at least very regularly, you could put the functionality in a foreground service. Foreground services are not effected by doze.
You should be aware that you should have a good reason to use a foreground service since the user is aware of them, but I think you have one with the health monitoring etc.
Note: You should only use a foreground service for tasks the user expects the system to execute immediately or without interruption. Such cases include uploading a photo to social media, or playing music even while the music-player app is not in the foreground. You should not start a foreground service simply to prevent the system from determining that your app is idle.
From here.

Can Pusher messages be received on Android/iOS app when the app is closed or phone is turned off

Can Pusher messages be received on Android/iOS app when the app is closed or the phone is turned off?
What i expect to happen...
When phone is on & app is on, it's pretty straight forward from the Pusher docs on how to react to pusher messages sent to the app.
When phone is on & app is closed, the phone should receive a notification that something has been sent to the app.
When phone is turned off, a notification should be received by the phone when it's turned back on to notify that something has been sent to the app.
Are these even possible? If yes, what are some suggestions to lookout for? If no, what can be some workaround?

When an application using Pusher moves into the background on iOS and Android the connection to Pusher will likely stay active for a few minutes. But eventually that connection will be closed. You can't stop that happening within your application (although there may be a "hack" around stating your app is a Voice app when submitting to the Apps store).
Therefore, you should monitor your application moving to the background and put a fallback in place to delivery messages to the phone when it's not connected.
Please see How get pusher events when the iOS app go to the background? for libPusher (the Pusher iOS library).
Here's an extract from the Android Processes & Threads Lifecycle docs on a "Service Process":
A process that is running a service that has been started with the startService() method and does not fall into either of the two higher categories. Although service processes are not directly tied to anything the user sees, they are generally doing things that the user cares about (such as playing music in the background or downloading data on the network), so the system keeps them running unless there's not enough memory to retain them along with all foreground and visible processes.
So, running a Pusher instance in such a thread is a viable option.
However, there will still be occasions where the user goes offline. In that situation your server you can detect if a user is online by querying the Pusher HTTP API or by using WebHooks where your server can be instantly informed if the user has gone offline or come back online.
Using the mechanisms above you can facilitate smart notifications; if the user is online (the app is in the foreground) then send the message to them by Pusher, if they are offline (the app is in the background) then use an alternative mechanism for delivery (native Push Notification, SMS or email).