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randdusing / cordova-plugin-bluetoothle

Bluetooth Low Energy Phonegap Plugin
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Android 8 not sending timely Bluetooth events when in Doze/ App Standby mode #490

Open benhtn opened 6 years ago

benhtn commented 6 years ago

I am attempting to create an Ionic v1 app the purpose of which is to maintain a connection to a bluetooth LE device and notify the user if it disconnects (along with trying to reconnect etc) using the Angular wrapped version of this plugin.

However during testing on Android 8.0 I've found that the appropriate callback isn't being called upon disconnection in anything like a timely fashion (it seems to wait until the next OS maintenance window, as explained here: https://developer.android.com/training/monitoring-device-state/doze-standby) when the device is in a sleep/ doze state. See example below:

    $cordovaBluetoothLE.connect({
        address: address,
        timeout: timeout
    }).then(
        null, 
        function(e) {
            return onConnectError(e);
        }, 
        function(result) { // this does not happen in a timely way when device is dozing
            if(result.status === "connected") {
                onConnected(result);
            } else {
                onDisconnected(result);
            }
        }
    );

I have tried the following (on a Moto G6 running Android 8.0):

randdusing commented 6 years ago

Same behavior across Android devices and versions? I don't remember running into many issues with Android and background modes, but it's been a while since I've done any BLE work.

bramk commented 5 years ago

Any new insights on this?

I have a strange but similar case with the same setup as @benhtn. In addition, after the BLE device is connected, I subscribe to a service that sends me data at about 50hz. This worked fine before and still does while the app is in the foreground. However, on devices running Android 8+ I now no longer receive the disconnected notification while I still do still receive data once the app is in "doze mode".

More detail:

  1. When the app is in the foreground I receive the subscribedResult notifications and disconnected notifications on the respective callbacks as expected.

  2. When I move the app into the background this still works for about 5 minutes. I assume at this point the app enters "doze mode".

  3. In "doze mode" I still receive the subscribedResult notifications as long as the BLE device is connected, but when it disconnects I do not receive the disconnected notification.

  4. Once I move the app in "doze mode" back into the foreground I immediately do receive the pending disconnected notification.

App setup:

bramk commented 5 years ago

Ok, my problem was a result of incorrectly use of the cordova-plugin-background-mode plugin. It turns out that calling disableWebViewOptimizations() only works if you call it after the app goes into the background. So as a result my webview went into "doze" mode and maybe that was what happend to @benhtn too.

So, through it is still a riddle to me why I did receive subscribedResult notifications and not disconnected notifications, my problem is now solved.