Question

I am trying to access the indexeddb from my app (so I can update a live tile) in a javascript background task.

I am setting up the task like so:

        var builder = new Windows.ApplicationModel.Background.BackgroundTaskBuilder();
        builder.name = taskName;
        builder.taskEntryPoint = "js\\task\\backgroundTask.js";

        //Run every 8 hours if the device is on AC power
        var trigger = new Windows.ApplicationModel.Background.MaintenanceTrigger(480, false);
        builder.setTrigger(trigger);

        var task = builder.register();

The task looks like this:

(function () {
    "use strict";

    var backgroundTaskInstance = Windows.UI.WebUI.WebUIBackgroundTaskInstance.current;
    var cancel = false;

    function doWork() {
        var key = null, settings = Windows.Storage.ApplicationData.current.localSettings;

        //todo access db and update tile

        close();
    }

    if (!cancel) {
        doWork();
    } else {
        close();
    }

    function onCanceled(cancelSender, cancelReason) {
        cancel = true;
    }

    backgroundTaskInstance.addEventListener("canceled", onCanceled);

})();

The task seems to work fine but I can’t work out if I can access the db (or any of the apps resources). Is this sort of thing even possible, if so what have I missed?

Answer 1

According to http://msdn.microsoft.com/en-us/library/windows/apps/hh453270.aspx, the WorkerGlobalScope in a Store app, which is in effect when you’re in a background task, makes indexedDB available. IndexedDB works within local appdata, so should be usable as any other appdata operations.

Generally speaking, background tasks can modify app data and issue tile/toast/badge updates. As Slace points out, you can’t access other app resources, so appdata is how you share data with the main app.