2015-09-02 12:12:22 +00:00
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# 在线/离线事件探测
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2017-01-17 09:50:16 +00:00
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2015-09-02 12:12:22 +00:00
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使用标准 HTML5 APIs 可以实现在线和离线事件的探测，就像以下例子：
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2016-10-03 23:40:51 +00:00
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_main.js_
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2015-12-19 06:27:47 +00:00
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```javascript
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2016-10-03 23:40:51 +00:00
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const {app, BrowserWindow} = require('electron')
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let onlineStatusWindow
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2015-09-02 12:12:22 +00:00
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2016-10-03 23:40:51 +00:00
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app.on('ready', () => {
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2016-10-03 03:47:16 +00:00
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onlineStatusWindow = new BrowserWindow({ width: 0, height: 0, show: false })
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2016-10-03 22:48:04 +00:00
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onlineStatusWindow.loadURL(`file://${__dirname}/online-status.html`)
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2016-10-03 03:47:16 +00:00
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})
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2015-12-19 06:27:47 +00:00
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```
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2015-09-02 12:12:22 +00:00
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2016-10-03 23:40:51 +00:00
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_online-status.html_
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2015-12-19 06:27:47 +00:00
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```html
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2015-09-02 12:12:22 +00:00
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<!DOCTYPE html>
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<html>
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2016-10-03 23:40:51 +00:00
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<body>
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<script>
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const alertOnlineStatus = () => {
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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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2015-09-02 12:12:22 +00:00
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</html>
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2015-12-19 06:27:47 +00:00
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```
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2015-09-02 12:12:22 +00:00
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2016-06-15 11:30:02 +00:00
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也会有人想要在主进程也有回应这些事件的实例。然后主进程没有 `navigator` 对象因此不能直接探测在线还是离线。使用 Electron 的进程间通讯工具，事件就可以在主进程被使用，就像下面的例子：
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2015-09-02 12:12:22 +00:00
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*main.js*
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2017-01-17 09:50:16 +00:00
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2015-12-19 06:27:47 +00:00
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```javascript
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2017-01-17 09:50:16 +00:00
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const {app, BrowserWindow, ipcMain} = require('electron')
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let onlineStatusWindow
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2015-09-02 12:12:22 +00:00
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2017-01-17 09:50:16 +00:00
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app.on('ready', () => {
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2016-10-03 03:47:16 +00:00
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onlineStatusWindow = new BrowserWindow({ width: 0, height: 0, show: false })
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2016-10-03 22:48:04 +00:00
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onlineStatusWindow.loadURL(`file://${__dirname}/online-status.html`)
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2016-10-03 03:47:16 +00:00
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})
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2015-09-02 12:12:22 +00:00
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2017-01-17 09:50:16 +00:00
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ipcMain.on('online-status-changed', (event, status) => {
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2016-10-03 03:47:16 +00:00
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console.log(status)
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})
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2015-12-19 06:27:47 +00:00
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```
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2015-09-02 12:12:22 +00:00
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*online-status.html*
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2017-01-17 09:50:16 +00:00
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2015-12-19 06:27:47 +00:00
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```html
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2015-09-02 12:12:22 +00:00
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<!DOCTYPE html>
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<html>
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2017-01-17 09:50:16 +00:00
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<body>
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<script>
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const {ipcRenderer} = require('electron')
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const updateOnlineStatus = () => {
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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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2015-09-02 12:12:22 +00:00
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</html>
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2015-12-19 06:27:47 +00:00
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```
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2017-01-17 09:50:16 +00:00
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**注意：** 如果 Electron 无法连接到局域网（LAN）或
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一个路由器，它被认为是离线的; 所有其他条件返回 `true`。
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所以，虽然你可以假设 Electron 是离线的，当 `navigator.onLine`
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返回一个 `false' 值，你不能假设一个 'true' 值必然
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意味着 Electron 可以访问互联网。你可能会获得虚假
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连接，例如在计算机运行虚拟化软件的情况下，
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具有始终“连接”的虚拟以太网适配器。
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因此，如果您真的想确定 Electron 的互联网访问状态，
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你应该开发额外的检查手段。
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