页面刷新后，Chrome API警报停止

Question

Reading around, I was under the impression that the Chrome alarm continues to work even after Chrome is closed, page refreshed etc. From one of the Google results:

With the Chrome alarm APIs, you can set an alarm that lasts as long as the app is installed, even if its background page goes inactive.

My problem is that I have setup a Chrome alarm in my options.js page for a Chrome Extension. The alarm is created (chrome.alarms.create) when the options page is saved.

The alarm works if I keep my page open. However, if I reload the page (options.html), I don't get the alarms anymore.

Here is part of my options.js

$('#save-options-button').on('click', function() {

    //Clears existing alarm
    chrome.alarms.clearAll();

    //Create alarm
    chrome.alarms.create("fetchAlarm", {
        delayInMinutes: 1,
        periodInMinutes: 1
    });

    chrome.alarms.onAlarm.addListener(function(alarm) {
        console.log("Got an alarm!", alarm);

    });
});

Answer 1

I guess you are quoting the Chrome Apps documentation, that's why it gets confusing.

What was meant is that event pages (a type of background page ) will be woken up to serve an alarm event even if they were unloaded for being idle.

This applies only to event/background pages. Chrome would not randomly open a page only because an event that the page listened to in the past happened. As such, you should not put actual event listener logic into UI pages (options, popup, etc.)

In your case, refreshing the page makes the JS context that contained the listener to be destroyed along with it, and your logic only adds a listener after a click. Even if you added that addListener to the top level code instead, it would only function as long as the page is open.

So, you will need to add a background page to service that event (the actual listener).

A background page is normally always ready to answer events. Event pages are special in that Chrome remembers which events should trigger their load and doesn't keep them loaded. You can read more about it in another answer of mine .