2014-11-05 07:47:38 -07:00
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# Online/Offline Event Detection
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Online and offline event detection can be implemented in the renderer process
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using standard HTML5 APIs, as shown in the following example.
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_main.js_
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```javascript
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2015-11-12 21:20:09 +08:00
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const electron = require('electron');
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const app = electron.app;
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const BrowserWindow = electron.BrowserWindow;
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2014-11-05 07:47:38 -07:00
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2016-05-04 12:11:51 -06:00
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let onlineStatusWindow;
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app.on('ready', () => {
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2014-11-05 07:47:38 -07:00
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onlineStatusWindow = new BrowserWindow({ width: 0, height: 0, show: false });
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2016-05-04 12:11:51 -06:00
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onlineStatusWindow.loadURL(`file://${__dirname}/online-status.html`);
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2014-11-05 07:47:38 -07:00
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});
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```
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_online-status.html_
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```html
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2015-03-04 21:29:02 +08:00
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<!DOCTYPE html>
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2014-11-05 07:47:38 -07:00
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<html>
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2015-11-10 16:48:24 +08:00
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<body>
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<script>
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2016-05-04 12:11:51 -06:00
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const alertOnlineStatus = () => {
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2015-11-10 16:48:24 +08:00
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window.alert(navigator.onLine ? 'online' : 'offline');
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};
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window.addEventListener('online', alertOnlineStatus);
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window.addEventListener('offline', alertOnlineStatus);
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alertOnlineStatus();
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</script>
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</body>
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2014-11-05 07:47:38 -07:00
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</html>
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```
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2015-08-31 19:17:59 -07:00
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There may be instances where you want to respond to these events in the
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main process as well. The main process however does not have a
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`navigator` object and thus cannot detect these events directly. Using
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2015-04-16 11:31:12 +08:00
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Electron's inter-process communication utilities, the events can be forwarded
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2015-03-26 10:20:31 -05:00
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to the main process and handled as needed, as shown in the following example.
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2014-11-05 07:47:38 -07:00
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_main.js_
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```javascript
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2015-11-12 21:20:09 +08:00
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const electron = require('electron');
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const app = electron.app;
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const ipcMain = electron.ipcMain;
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const BrowserWindow = electron.BrowserWindow;
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2014-11-05 07:47:38 -07:00
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2016-05-04 12:11:51 -06:00
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let onlineStatusWindow;
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app.on('ready', () => {
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2014-11-05 07:47:38 -07:00
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onlineStatusWindow = new BrowserWindow({ width: 0, height: 0, show: false });
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2016-05-04 12:11:51 -06:00
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onlineStatusWindow.loadURL(`file://${__dirname}/online-status.html`);
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2014-11-05 07:47:38 -07:00
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});
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2016-05-04 12:11:51 -06:00
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ipcMain.on('online-status-changed', (event, status) => {
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2014-11-05 07:47:38 -07:00
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console.log(status);
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});
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```
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_online-status.html_
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```html
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2015-03-04 21:29:02 +08:00
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<!DOCTYPE html>
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2014-11-05 07:47:38 -07:00
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<html>
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2015-11-10 16:48:24 +08:00
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<body>
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<script>
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2016-05-11 01:26:38 +09:00
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const {ipcRenderer} = require('electron');
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2016-05-04 12:11:51 -06:00
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const updateOnlineStatus = () => {
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2015-11-10 16:48:24 +08:00
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ipcRenderer.send('online-status-changed', navigator.onLine ? 'online' : 'offline');
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};
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window.addEventListener('online', updateOnlineStatus);
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window.addEventListener('offline', updateOnlineStatus);
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updateOnlineStatus();
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</script>
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</body>
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2014-11-05 07:47:38 -07:00
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</html>
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```
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