Why won't CefSharp.PostMessage work in CefSharp browser?-CodePudding

I tried using JavascriptMessageReceived event in c# to handle CefSharp.PostMessage called from JS within the browser. I even downloaded an example of this working from link. Ran example which was supposed to do exactly what I needed, but it didn't work, nor does my code (below). Did CefSharp remove this functionality or change it? Do I need to enable this feature within the CefSettings or ChromiumWebBrowser?

using CefSharp;
using CefSharp.WinForms;

public ChromiumWebBrowser chromeBrowser;

public Form1()
    {
        InitializeComponent();

        string curDir = Directory.GetCurrentDirectory();
        CefSettings settings = new CefSettings();
        Cef.Initialize(settings);
        chromeBrowser = new ChromiumWebBrowser(String.Format("file:///{0}/HelloWorld.html", curDir));
        chromeBrowser.JavascriptMessageReceived  = ChromeBrowser_JavascriptMessageReceived;
    }

private void ChromeBrowser_JavascriptMessageReceived(object sender, JavascriptMessageReceivedEventArgs e)
    {
        MessageBox.Show((string)e.Message);
    }

HelloWorld.html here

<!DOCTYPE html>
<html>
<body>

<script>
CefSharp.PostMessage("Hello world!");
</script>

</body>
</html>

CodePudding user response：

CefSharp.PostMessage("Hello world!"); is a quite new JS extension of 2020. Make sure your are using the actual CefSharp.

chromeBrowser = new ChromiumWebBrowser(String.Format("file:///{0}/HelloWorld.html", curDir));
chromeBrowser.JavascriptMessageReceived  = ChromeBrowser_JavascriptMessageReceived;

The subscription on JavascriptMessageReceived events is too late, the page might be downloaded and JS might be executed to that moment. You should subscribe on events before page load.

chromeBrowser = new ChromiumWebBrowser("about:blank");
chromeBrowser.JavascriptMessageReceived  = ChromeBrowser_JavascriptMessageReceived;
chromeBrowser.Load(String.Format("file:///{0}/HelloWorld.html", curDir));

Make sure HelloWorld.html is existing in the application current working directory.

CodePudding user response：

Where are you adding the ChromiumWebBrowser to the form? The WinForms ChromiumWebBrowser control won't load until it's handle is created which by default happens when it's added to a parent.

chromeBrowser = new ChromiumWebBrowser(String.Format("file:///{0}/HelloWorld.html", curDir));
chromeBrowser.JavascriptMessageReceived  = ChromeBrowser_JavascriptMessageReceived;
Controls.Add(chromeBrowser);