2015-09-02 12:12:22 +00:00
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# 在线/离线事件探测
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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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*main.js*
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2015-12-19 06:27:47 +00:00
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```javascript
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2015-09-02 12:12:22 +00:00
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var app = require('app');
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var BrowserWindow = require('browser-window');
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var onlineStatusWindow;
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app.on('ready', function() {
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onlineStatusWindow = new BrowserWindow({ width: 0, height: 0, show: false });
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2015-11-24 12:02:14 +00:00
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onlineStatusWindow.loadURL('file://' + __dirname + '/online-status.html');
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2015-09-02 12:12:22 +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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*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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<body>
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<script>
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var alertOnlineStatus = function() {
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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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</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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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，就像下面的例子：
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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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2015-09-02 12:12:22 +00:00
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var app = require('app');
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var ipc = require('ipc');
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var BrowserWindow = require('browser-window');
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var onlineStatusWindow;
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app.on('ready', function() {
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onlineStatusWindow = new BrowserWindow({ width: 0, height: 0, show: false });
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2015-11-24 12:02:14 +00:00
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onlineStatusWindow.loadURL('file://' + __dirname + '/online-status.html');
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2015-09-02 12:12:22 +00:00
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});
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ipc.on('online-status-changed', function(event, status) {
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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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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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<body>
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<script>
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var ipc = require('ipc');
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var updateOnlineStatus = function() {
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ipc.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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</html>
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2015-12-19 06:27:47 +00:00
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```
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