toga webview load local html file

[Jzhenli]

Hi, if it's possible for webview widget to load local html file? In some case we want to display a customized page before loading the remote web url.

[mhsmith]

As it says in the documentation:

Due to app security restrictions, WebView can only display http:// and https:// URLs, not file:// URLs. To serve local file content, run a web server on localhost using a background thread.

This could be as simple as using the standard library http.server module as shown here.

[mhsmith]

In that case you'd probably need two WebViews, a visible one showing the local HTML, and an invisible one loading the remote URL, and then switch them when the remote URL has loaded.

For a fixed delay, you could use App.loop to call call_later for a regular function, or create_task for an async function which starts off with an async sleep.

Even better would be to use use the on_webview_load event, but unfortunately that isn't supported on Android yet.

[Jzhenli]

@mhsmith Hi, I try to load a local html file in the android webview, but it can not display, not sure if it's a bug? attached is my test html file.
html.zip

[freakboy3742]

Based on the detail you've provided, it's impossible to tell if it is "not displaying" because of how you're using the widget.

However, assuming you're using WebView.set_content() correctly, there's very little we can do to debug what is going on. We don't have any insight into the internals of the WebView - it's a widget provided by Android, and we're using it. If you can display a simple <h1>Hello World</h1> page, but your HTML content doesn't load, then you're at the point of diagnosing either your own HTML, or the limitations of Android's webview.

[Jzhenli]

@freakboy3742 I have find the root cause, I have changed the "color: #f00" to "color: %23f00" in the html file, then it will display well. So I doubt in the WebView.set_content(), maybe toga have implemented it with loaddata(), from the android api, we can find that when html file have '#', '%', '', '?' should be replaced by %23, %25, %27, %3f respectively. If you implemented it with loadDataWithBaseURL() maybe avoid this issue.

[freakboy3742]

Ah - in which case, that's a known issue: see #2242. The proposed fix on that ticket is to use Python to encode the payload passed to loadData() - but loadDataWithBaseURL() may also be a viable fix. PRs to address the problem are welcome.