In version 3, all reconnection logic is now handled via the ReconnectFilter interface. There are a few default implementations already provided, and most of the time you shouldn't have to adjust these.
When dealing with reconnections, it's important to note the distinction between the two methods in the ReconnectFilter interface.
onConnectFailed(ConnectFailEvent) - This method is called when the library fails to establish a connection to a BleDevice when it was not connected prior. This will only be called if the BleDevice is not in either the RECONNECTING_SHORT_TERM or RECONNECTING_LONG_TERM state.
onConnectionLost() - The method is called by the library when we previously had a connection to the device (it was in the
CONNECTED state), but have since lost that connection. This method is related to the states RECONNECTING_SHORT_TERM and RECONNECTING_LONG_TERM
Default implementation of DeviceReconnectFilter (which extends
ReconnectFilter). This class has a few constructors which allow you to change the default settings for the filter (how many attempts to retry a connection, how long the library should try to establish a reconnection, etc.). The defaults are:
Retry failed connection attempts twice (for a total of 3 connection attempts)
Retry connecting lost connections
Short term reconnect runs a total of 5 seconds, with 1 second between each retry
Long term reconnect runs a total of 5 minutes, with 5 seconds of delay between each retry
Best practice - Like above, it's best practice to extend the DefaultServerReconnectFilter for handling reconnection logic.
If you are going to use a custom filter, then you should understand how the onConnectionLost() method is used. (onConnectFailed() is pretty straightforward, and everything you need to know about it is listed in the beginning of this document).
When a device loses its established connection, onConnectionLost() is called. The library first needs to know if it should continue reconnecting. What you return here will affect how the method gets called again. If you return with either ConnectionLostPlease.retryWithTimeout or ConnectionLostPlease.retryInstantlyWithTimeout, onConnectionLost() will not be called again (until you get a connection established, and then drops again, forcing another reconnection attempt). Otherwise, if you tell the library to continue retrying, the method will be called again to get the delay time before trying to reconnect. Also in this case, the method will get called each time it needs to try to reconnect.