Intercept and override HTTP requests from WebView

Question

I have a WebView in my application in which some site is opened (always the same, it is my own page). The site has some JS code that loads some images from the remote host.

I want to intercept requests to such images (by URL pattern) and give back my own content (i.e. another image), or leave request untouched depending on internal application logic.

Is it possible to do that?

EDIT: The current state of the question...

WebView has the ability to set a WebViewClient (as noted by Axarydax). WebViewClient have two useful methods

• shouldOverrideUrlLoading
• onLoadResource

shouldOverrideUrlLoading is able to intercept any URL loading, if loading is triggered by page interaction (i.e. link on a page is clicked, WebView.loadURL("") isn't triggering this method). It is also able to cancel URL loading by returning false. This approach isn't usable, cause' it is not able to intercept loading of page resources (and images, what I need to intercept, is such a page resource).

onLoadResource is triggering every time that page resource (and images! thx to Jessyjones) are loading, but there is no way to cancel that. That makes this method not suitable for my task also.

Answer 1

Try this, I've used it in a personal wiki-like app:

webView.setWebViewClient(new WebViewClient() {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if (url.startsWith("foo://")) {
            // magic
            return true;
        }
        return false;
    }
});

Answer 2

It looks like API level 11 has support for what you need. See WebViewClient.shouldInterceptRequest().

Answer 3

As far as I know, shouldOverrideUrlLoading is not called for images but rather for hyperlinks... I think the appropriate method is

@Override public void onLoadResource(WebView view, String url)

This method is called for every resource (image, styleesheet, script) that's loaded by the webview, but since it's a void, I haven't found a way to change that url and replace it so that it loads a local resource ...