建立应用侧与前端页面数据通道
前端页面和应用侧之间可以用createWebMessagePorts()接口创建消息端口来实现两端的通信。
在下面的示例中，应用侧页面中通过createWebMessagePorts方法创建两个消息端口，再把其中一个端口通过postMessage()接口发送到前端页面，便可以在前端页面和应用侧之间互相发送消息。端口使用完毕后或Webview对象销毁前通过close接口关闭端口。
-
应用侧代码。
// xxx.ets import { webview } from '@kit.ArkWeb'; import { BusinessError } from '@kit.BasicServicesKit'; @Entry @Component struct WebComponent { controller: webview.WebviewController = new webview.WebviewController(); ports: webview.WebMessagePort[] = []; @State sendFromEts: string = 'Send this message from ets to HTML'; @State receivedFromHtml: string = 'Display received message send from HTML'; build() { Column() { // 展示接收到的来自HTML的内容 Text(this.receivedFromHtml); // 输入框的内容发送到HTML TextInput({ placeholder: 'Send this message from ets to HTML' }) .onChange((value: string) => { this.sendFromEts = value; }) // 该内容可以放在onPageEnd生命周期中调用。 Button('postMessage') .onClick(() => { try { // 1、创建两个消息端口。 this.ports = this.controller.createWebMessagePorts(); if (this.ports && this.ports[0] && this.ports[1]) { // 2、在应用侧的消息端口(如端口1)上注册回调事件。 this.ports[1].onMessageEvent((result: webview.WebMessage) => { let msg = 'Got msg from HTML:'; if (typeof (result) === 'string') { console.info(`received string message from html5, string is: ${result}`); msg = msg + result; } else if (typeof (result) === 'object') { if (result instanceof ArrayBuffer) { console.info(`received arraybuffer from html5, length is: ${result.byteLength}`); msg = msg + 'length is ' + result.byteLength; } else { console.info('not support'); } } else { console.info('not support'); } this.receivedFromHtml = msg; }) // 3、将另一个消息端口(如端口0)发送到HTML侧，由HTML侧保存并使用。 this.controller.postMessage('__init_port__', [this.ports[0]], '*'); } else { console.error(`ports is null, Please initialize first`); } } catch (error) { console.error(`ErrorCode: ${(error as BusinessError).code}, Message: ${(error as BusinessError).message}`); } }) // 4、使用应用侧的端口给另一个已经发送到html的端口发送消息。 Button('SendDataToHTML') .onClick(() => { try { if (this.ports && this.ports[1]) { this.ports[1].postMessageEvent(this.sendFromEts); } else { console.error(`ports is null, Please initialize first`); } } catch (error) { console.error(`ErrorCode: ${(error as BusinessError).code}, Message: ${(error as BusinessError).message}`); } }) // 5、关闭端口。 Button('closePort') .onClick(() => { try { if (this.ports && this.ports.length == 2) { this.ports[0].close(); this.ports = []; } else { console.error("ports is null, not need close"); } } catch (error) { console.error(`ErrorCode: ${(error as BusinessError).code}, Message: ${(error as BusinessError).message}`); } }) Web({ src: $rawfile('index.html'), controller: this.controller }) } } } -
前端页面代码。
<!--index.html--> <!DOCTYPE html> <html> <head> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>WebView Message Port Demo</title> </head> <body> <h1>WebView Message Port Demo</h1> <div> <input type="button" value="SendToEts" onclick="PostMsgToEts(msgFromJS.value);"/><br/> <input id="msgFromJS" type="text" value="send this message from HTML to ets"/><br/> </div> <p class="output">display received message send from ets</p> </body> <script> var h5Port; var output = document.querySelector('.output'); window.addEventListener('message', function (event) { if (event.data === '__init_port__') { if (event.ports[0] !== null) { h5Port = event.ports[0]; // 1. 保存从应用侧发送过来的端口。 h5Port.onmessage = function (event) { // 2. 接收ets侧发送过来的消息。 var msg = 'Got message from ets:'; var result = event.data; if (typeof(result) === 'string') { console.info(`received string message from ets, string is: ${result}`); msg = msg + result; } else if (typeof(result) === 'object') { if (result instanceof ArrayBuffer) { console.info(`received arraybuffer from ets, length is: ${result.byteLength}`); msg = msg + 'length is ' + result.byteLength; } else { console.info('not support'); } } else { console.info('not support'); } output.innerHTML = msg; } } } }) // 3. 使用h5Port向应用侧发送消息。 function PostMsgToEts(data) { if (h5Port) { h5Port.postMessage(data); } else { console.error('h5Port is null, Please initialize first'); } } </script> </html>
常见问题
为什么H5向应用侧发送消息接收不到？
检查传递的数据类型是否正确，WebMessage支持的数据类型有string和ArrayBuffer。
如果想要传递对象类型则需要将对象类型通过JSON.stringify方法转换为string类型再进行传递。示例如下：
function PostMsgToEts(data) {
if (h5Port) {
let obj = {name:'exampleName',id:10}
h5Port.postMessage(JSON.stringify(obj));
} else {
console.error('h5Port is null. Please initialize it first.');
}
}