Android BLE BluetoothGatt object remains connected and triggers onCharacteristicChanged() even after a call to disconnect()

Question

I am trying to disconnect characteristic notifications as I am exiting my app. Here is how I am doing it in my exitCleanup() function:

if (btGatt != null && mWriteChar != null) {
   boolean b=btGatt.setCharacteristicNotification(mWriteChar, false);
   Log.w("AppInfo", "Exiting and Unsubscribing: " + b);
}

The log shows: Exiting and Unsubscribing: true. So far so good. I then attempt to disconnect the GATT object altogether using the following:

if (btGatt != null && btManager!=null && btManager.getConnectionState(btDevice, BluetoothProfile.GATT) != BluetoothProfile.STATE_DISCONNECTED ) {
    //Making sure that gatt and bt manager are still with us
    //Also making sure that the connection state is NOT disconnected
    btGatt.disconnect();
    btGatt.close();
    Log.w( "AppInfo", "FINISHING. Connection state=" + btManager.getConnectionState(btDevice, BluetoothProfile.GATT) );
}

This is where things get weird. The log now displays the following: FINISHING. Connection state=2, indicating that the BluetoothDevice is still connected.

This is a problem, because when the app finishes and destroys all the assets, the BluetoothGattCallback still continues to receive notifications behind the scenes. First it throws the following NullPointerException:

04-25 22:49:54.392  17280-17293/com.myapp.appinfo D/BluetoothGatt﹕ onClientConnectionState() - status=0 clientIf=8 device=54:4A:16:26:A1:B5
04-25 22:49:54.392  17280-17293/com.myapp.appinfo W/BluetoothGatt﹕ Unhandled exception in callback
java.lang.NullPointerException
        at android.bluetooth.BluetoothGatt$1.onClientConnectionState(BluetoothGatt.java:168)
        at android.bluetooth.IBluetoothGattCallback$Stub.onTransact(IBluetoothGattCallback.java:71)
        at android.os.Binder.execTransact(Binder.java:404)
        at dalvik.system.NativeStart.run(Native Method)
04-25 22:49:54.402  17280-17280/com.myapp.appinfo D/BluetoothManager﹕ getConnectionState()

And then continues to publish onNotify() calls that trigger onCharacteristicChanged() calls even after the app has terminated awile ago:

D/BluetoothGatt﹕ onNotify() - Device=54:4A:16:26:A1:B5 UUID=0000ffe1-0000-1000-8000-00805f9b34fb

Any advice on how to properly disconnect from GATT characteristic notifications when exiting from an app?

Answer 1

It seems you can't call these method together. The disconnection callback might arrive later than close() method performed.

You can add mGatt.close(); into onConnectionStateChange callback to close the connection.

https://code.google.com/p/android/issues/detail?id=183108