详解HTML5中的消息通信代码-H5教程

HTML5支持跨文档消息通信(Cross-Document Messaging)。

既然使用到消息通信，那么必然有事件(event)产生。根据事件的产生和消费，我们能够找到发送者和接收者，也就是Sender和Listener。

其中Litener需要做如下的工作：

编写一个消息处理函数；
将消息处理函数注册：addEventListener('message', function, false);

其中Sender需要做以下工作：

postMessage('this is a message', 'http://www.erdangjiade.com');

事件对象event中包含的成员包括：

data：传递的数据；
origin：origin，origin包括三要素：主机、协议、端口；
source：来源对象；

好了，下面我们看一个例子，这个例子展示了在页面中嵌套页面并且向子页面发送消息：

父页面如下：

<!DOCTYPE html>
<html lang="en">

<!-- 
    crossDomain.html by Bill Weinman 
    <http://bw.org/contact/>
    created 2011-04-16

    Copyright (c) 2011 The BearHeart Group, LLC
    This file may be used for personal educational purposes as needed. 
    Use for other purposes is granted provided that this notice is
    retained and any changes made are clearly indicated as such. 
-->

<head>
    <title>
        HTML5 Messaging Template File (One)
    </title>
    <link rel="stylesheet" type="text/css" href="../CSS/main.css">
    <style>
        #frameTwo {
            float: left;
            width: 500px;
            height: 400px;
            margin: 0 5px;
            padding: 3px;
            border-top: 2px solid #3c6b92;
            border-left: 2px solid #3c6b92;
            border-bottom: 2px solid #ccc;
            border-right: 2px solid #ccc;
        }
        #content { height: 500px; }
    </style>
    <script type="text/javascript">
		// 域名
        var originTwo = 'http://two.3sn.net';
		// URL地址
        var URLTwo = 'http://two.3sn.net/H5Msg/ExerciseFiles/Chap01/crossDomainTwo.html';
        var windowTwo = null;

        function handleMessage(event) {
			// 判断源区域
            if (event.origin == originTwo) {
                if(!windowTwo) windowTwo = event.source;
                log('message from origin: ' + event.origin);
                log(event.data);
				// 发送消息
                windowTwo.postMessage('this is from windowOne!', originTwo);
                log('message sent back to windowTwo');
            } else {
                dispError('message from untrusted origin: ' + event.origin);
            }
        }


        function init() {
			// 添加消息处理函数
		    window.addEventListener("message", handleMessage, false);
            window.onerror = windowErrorHandler;
            log('this is windowOne');
            log('host: ' + location.host);
			
			// load two页面
            element('frameTwo').src = URLTwo;   // load the frame
        }

        // ##### Utilities #####

        // shortcut for getElementById
        function element(id) { return document.getElementById(id); }

        function clearDisp() {
            element('pageResults').innerHTML = '';
            element('message').innerHTML = '';
            element('message').className = '';
        }

        function dispMessage(message) {
            m = element('message');
            m.className = 'message';
            if(m.textContent.length > 0) {
                m.innerHTML += '<br />' + message;
            } else m.innerHTML = message;
        }

        function windowErrorHandler(message, filename, lineno) {
            dispError(message + ' (' + filename + ':' + lineno + ')' );
            return true;
        };

        function dispError(errorMessage) {
            element('pageResults').innerHTML += 
                errorMessage ? '<p class="error">' + errorMessage + '</p>n' : '';
        }

        function log(m) {
            if(m.length < 1) return;
            logElement = element('log');
            if(logElement.textContent.length > 0) logElement.innerHTML += '<br />';
            logElement.innerHTML += nowTimeString() + ' ' + m;
        }

        function nowTimeString() {
            var d = new Date();
            return numToString(d.getUTCHours(), 2) + ':' + numToString(d.getUTCMinutes(), 2) + ':' +
                numToString(d.getUTCSeconds(), 2) + '.' + numToString(d.getUTCMilliseconds(), 3);
        }

        function numToString( num, len ) {
            var num = num + '';
            while(num.length < len) num = '0' + num;
            return num;
        }

        window.onload = init;

    </script>
</head>

<body>

<p id="content">

    <h1> 
        HTML5 Messaging Template File (One)
    </h1>

    <p id="message"></p>
    <p id="pageResults"></p>

    <iframe id="frameTwo">
        <p>Your browser doesn't support the iFrame feature</p>
    </iframe>

    <p id="log" style="font-family: monospace"></p>

</p>
</body>
</html>

<!DOCTYPE html>
<html lang="en">

<!-- 
    crossDomain.html by Bill Weinman 
    <http://bw.org/contact/>
    created 2011-04-16

    Copyright (c) 2011 The BearHeart Group, LLC
    This file may be used for personal educational purposes as needed. 
    Use for other purposes is granted provided that this notice is
    retained and any changes made are clearly indicated as such. 
-->

<head>
    <title>
        HTML5 Messaging Template File (Two)
    </title>
    <link rel="stylesheet" type="text/css" href="../CSS/main.css">
    <script type="text/javascript">
        var originOne = 'http://one.3sn.net';

        function handleMessage(event) {
            if (event.origin == originOne) {
                log('message from origin: ' + event.origin);
                log(event.data);
            } else {
                dispError('message from untrusted origin: ' + event.origin);
            }
        }

        // ##### Init #####

        function init() {
            window.onerror = windowErrorHandler;    // addEventListener doesn't provide the right error object in Firefox
            window.addEventListener("message", handleMessage, false);
            log('this is windowTwo');
            log('host: ' + location.host);
            var windowOne = parent;
            windowOne.postMessage('this is from windowTwo!', originOne);
            log('message sent to windowOne');
        }

        // ##### Utilities #####

        // shortcut for getElementById
        function element(id) { return document.getElementById(id); }

        function clearDisp() {
            element('pageResults').innerHTML = '';
            element('message').innerHTML = '';
            element('message').className = '';
        }

        function dispMessage(message) {
            m = element('message');
            m.className = 'message';
            if(m.textContent.length > 0) {
                m.innerHTML += '<br />' + message;
            } else m.innerHTML = message;
        }

        function windowErrorHandler(message, filename, lineno) {
            dispError(message + ' (' + filename + ':' + lineno + ')' );
            return true;
        };

        function dispError(errorMessage) {
            element('pageResults').innerHTML += 
                errorMessage ? '<p class="error">' + errorMessage + '</p>n' : '';
        }

        function log(m) {
            if(m.length < 1) return;
            logElement = element('log');
            if(logElement.textContent.length > 0) logElement.innerHTML += '<br />';
            logElement.innerHTML += nowTimeString() + ' ' + m;
        }

        function nowTimeString() {
            var d = new Date();
            return numToString(d.getUTCHours(), 2) + ':' + numToString(d.getUTCMinutes(), 2) + ':' +
                numToString(d.getUTCSeconds(), 2) + '.' + numToString(d.getUTCMilliseconds(), 3);
        }

        function numToString( num, len ) {
            var num = num + '';
            while(num.length < len) num = '0' + num;
            return num;
        }

        window.onload = init;

    </script>
</head>

<body>

<p id="content">

    <h1> 
        HTML5 Messaging Template File (Two)
    </h1>

    <p id="message"></p>
    <p id="pageResults"></p>
    <p id="log" style="font-family: monospace"></p>

</p>
</body>
</html>

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