[
https://issues.apache.org/jira/browse/CB-3901?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Bas Bosman updated CB-3901:
---------------------------
Component/s: Plugin Geolocation
> Backlog of Acceleration messages are received after plugin/sensor is stopped
> ----------------------------------------------------------------------------
>
> Key: CB-3901
> URL: https://issues.apache.org/jira/browse/CB-3901
> Project: Apache Cordova
> Issue Type: Improvement
> Components: Android, CordovaJS, Plugin Geolocation
> Affects Versions: 2.7.0
> Reporter: Peter
> Assignee: Joe Bowser
> Priority: Minor
>
> There is a kind of race condition between the Accelerometer events being
> generated and the processing of the Cordova bridge messages.
> For example:
> In the plugin:
> * Accelerometer events are generated at a rapid rate.
> * The event always results in data transfer across the bridge. e.g.
> onSensorChanged calls this.win() calls sendPluginResult…
> * So very quickly lots of PluginResult messages will be queued, requiring
> processing
> Meanwhile in the JavaScript:
> * callbackFromNative handles the incoming messages and if there are any
> listeners then it deals with the acceleration event.
> * When it determines there are no user listeners left then a sensor “stop”
> will be issued
> But even after the “stop” is executed, there is still a potentially large
> backlog of queued acceleration messages still remaining to be processed.
> Since there are no user listeners left the user does not get to see them –
> they so just end up going nowhere.
> I don’t know whether there is anything possible that can be done about this
> (it seems to be just the way it is designed) but perhaps there should be some
> comment in the code for the accelerometer callbacks to describe how they may
> be called even though all user listeners have been removed. And maybe the
> success function can be modified to not bother constructing the Acceleration
> instance unless it will be used. Something like this?
> BEFORE:
> {code}
> function(a) {
> var tempListeners = listeners.slice(0);
> accel = new Acceleration(a.x, a.y, a.z, a.timestamp);
> for (var i = 0, l = tempListeners.length; i < l; i++) {
> tempListeners[i].win(accel);
> }
> }
> {code}
> AFTER:
> {code}
> function(a) {
> // NB: It is possible for this callback to be executed even after the
> accelerometer
> // sensor is “stopped” due to a backlog of unprocessed acceleration
> messages.
> var tempListeners = listeners.slice(0);
> var nListeners = tempListeners.length;
> if (nListeners > 0) {
> accel = new Acceleration(a.x, a.y, a.z, a.timestamp);
> for (var i = 0, l = nListeners; i < l; i++) {
> tempListeners[i].win(accel);
> }
> }
> }
> {code}
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