Notifying the user of an update

However impressive a created display is it is unlikely to hold the user's attention forever and they are likely to switch to another application or browser tab. Luckily, HTML5 has a feature that will allow notifications on the desktop.

The main.dart function quakeUpdate checks if there is a significant update to notify the user about. To determine which item in the list to notify the user about, the lastWhere method is used. This List method finds the last item in the list that matches the criteria defined by the supplied function. In this case, we look at each feature's magnitude value (stored in gf[2]) and return true or false if the value meets the threshold:

quakeUpdate([Timer t = null]) async {
  await featPlotter.updateData();
  featPlotter.updateHotspots();
  quakeMap.drawMapGrid();

  List notiFeature =
      featPlotter.geoFeatures.lastWhere((List gf) => gf[2] > 1.9);

  String permResult = await Notification.requestPermission();
  if (permResult == 'granted') {
    Notification notifyQuake = new Notification('Quake Alert',
        body: 'Quake Update ${notiFeature[3]} - ${notiFeature[2]}');
  }
}

As this feature is potentially intrusive to a user's computer, the web page must ask for permission to show alerts. In Dartium, a prompt is shown at the top of the page requiring a yes or no response:

Once permission has been granted, the final step is to create an instance of the notification class. No further method call is required:

The application is set to notify quite often—you may wish to raise the level at which quakes are notified or you will find yourself dismissing a lot of notifications. The visual display of the notification may vary on different platforms and web browsers.