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。
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应用侧代码。
// xxx.etsimport { webview } from '@kit.ArkWeb';import { BusinessError } from '@kit.BasicServicesKit';@Entry@Componentstruct 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HTMLTextInput({ 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.');
}
}