harmony 鸿蒙建立应用侧与前端页面数据通道

2023-06-24
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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。

应用侧代码。

  // xxx.ets
  import web_webview from '@ohos.web.webview';
  import business_error from '@ohos.base';

  @Entry
  @Component
  struct WebComponent {
    controller: web_webview.WebviewController = new web_webview.WebviewController();
    ports: web_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;
          })

        Button('postMessage')
          .onClick(() => {
            try {
              // 1、创建两个消息端口。
              this.ports = this.controller.createWebMessagePorts();
              // 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: web_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 + 'lenght 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]], '*');
            } catch (error) {
              let e: business_error.BusinessError = error as business_error.BusinessError;
              console.error(`ErrorCode: ${e.code},  Message: ${e.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) {
              let e: business_error.BusinessError = error as business_error.BusinessError;
              console.error(`ErrorCode: ${e.code},  Message: ${e.message}`);
            }
          })
        Web({ src: $rawfile('xxx.html'), controller: this.controller })
      }
    }
  }

前端页面代码。

  <!--xxx.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ets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 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 + 'lenght is ' + result.byteLength;
                  } else {
                    console.info('not support');
                  }
                } else {
                  console.info('not support');
                }
                output.innerHTML = msg;
              }
          }
      }
  })

  // 3. 使用h5Port往ets侧发送消息.
  function PostMsgToEts(data) {
      if (h5Port) {
        h5Port.postMessage(data);
      } else {
        console.error('h5Port is null, Please initialize first');
      }
  }
  </script>
  </html>