CefSharp winfoms Page load and wait

问题

I'm working on Cefsharp Offscreen in my application. The code provided in documentation to load page is:

 const string testUrl = "https://github.com/cefsharp/CefSharp/wiki/Quick-Start";
  var settings = new CefSettings()
        {
   //By default CefSharp will use an in-memory cache, you need to specify a Cache Folder to persist data
   CachePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "CefSharp\\Cache")
        };

   //Perform dependency check to make sure all relevant resources are in our output directory.
   Cef.Initialize(settings, performDependencyCheck: true, browserProcessHandler: null);

   // Create the offscreen Chromium browser.
   browser = new ChromiumWebBrowser(testUrl);

   // An event that is fired when the first page is finished loading.
   // This returns to us from another thread.
   browser.LoadingStateChanged += BrowserLoadingStateChanged;
   Cef.Shutdown();

but I want something like that

browser = new ChromiumWebBrowser(); //without testUrl
 // and then 
browser.Load(testUrl).Wait();// and wait something like that;
// load url and wait unit page is fully loaded then go to next line

I couldn't find any solution.

回答1:

The CefSharp.OffScreen.Example.Program.cs class in the project source contains an example of using a TaskCompletionSource to wrap the LoadingStateChanged event so you can await the Page Load.

A basic example implemented as an extension method would look like:

public static class WebBrowserExtensions
{
    public static Task LoadPageAsync(this IWebBrowser browser, string address = null)
    {
        var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);

        EventHandler<LoadingStateChangedEventArgs> handler = null;
        handler = (sender, args) =>
        {
            //Wait for while page to finish loading not just the first frame
            if (!args.IsLoading)
            {
                browser.LoadingStateChanged -= handler;
                //Important that the continuation runs async using TaskCreationOptions.RunContinuationsAsynchronously
                tcs.TrySetResult(true);
            }
        };

        browser.LoadingStateChanged += handler;

        if (!string.IsNullOrEmpty(address))
        {
            browser.Load(address);
        }

        return tcs.Task;
    }
}

You can then write code like

browser = new ChromiumWebBrowser();
await browser.LoadPageAsync(testUrl);

The browser is written to be async and blocking using Task.Wait is not recommended nor supported. Use async/await.

回答2:

You have to set a flag and waiting for that flag.

private bool flag = false;

private void some_function(){

    browser = new ChromiumWebBrowser(); //without testUrl
    browser.Load(testUrl);
    browser.LoadingStateChanged += BrowserLoadingStateChanged;

    while(!flag)
    {
        Thread.Sleep(100);
    }
}
private void LoadingStateChanged(object sender, LoadingStateChangedEventArgs e)
{
    if (!e.IsLoading)
    {
        flag = true;
    }
}

This code looks boring. But you can encapsulate a chromium browser. Maybe you can use singleton pattern. And implement wait function.

来源：https://stackoverflow.com/questions/58241504/cefsharp-winfoms-page-load-and-wait

标签

cefsharp

cefsharp.offscreen