shouldOverrideUrlLoading in WebView for Android no

问题:

-Edit: Solution Found-
Figured it out after some heavy searching - one person (I literally mean one) said they instead used onPageLoad(); which worked perfectly for my purposes. The difference is that onPageLoad() runs later than shouldOverrideUrlLoading, but It doesn't make a difference in my code.

I'm trying to set up Twitter authorization with OAuth for an Android app, and thus far I can successfully send the user to the authorization URL, however, what I am trying to do now is intercept the redirect to the callback (which would just lead to a 404 error, our callback URL isn't going to have an associated page on our servers). What I'm attempting to do is check if the URL is our callback, then extract the OAuth Verifier from the URL. I setup my WebView with this code:

view = (WebView)findViewById(R.id.twitterWbVw);
view.setWebViewClient(new WebViewClient(){
    @Override
    public boolean shouldOverrideUrlLoading(WebView wView, String url)
    {
        String urlHolder;
        String[] verifExtrctr;
        urlHolder = url.substring(0, url.indexOf('?'));
        System.out.println("url");
        if(urlHolder.equalsIgnoreCase(CALLBACK_URL))
        {
            verifExtrctr = urlHolder.split("?");
            verifExtrctr = verifExtrctr[2].split("=");
            if(verifExtrctr[0].equalsIgnoreCase("oauth_verifier"))
            {
                params[5] = verifExtrctr[1];
                return true;
            }
            else
            {
                System.out.println("Inocorrect callback URL format.");
            }
        }
        else    
        {
            wView.loadUrl(url);
        }
        return true;
    }
});
view.loadUrl(urlAuthorize.toExternalForm());

Thing is even System.out.println("url");(which I'm using to debug)doesn't run! So I'm pretty much dry on ideas, and can't find anyone with a similar problem. The authorization URL goes through fine, and I can successfully authorize the app, however the redirect to the callback URL for some reason never get's intercepted. Any help would be appreciated, this is in my onResume() if that matters.

回答1:

After some research I conclude that despite what most of the tutorials out there say, shouldOverrideUrlLoading() does not get called when:

1. You load a URL like

   loadUrl("http://www.google.com");
   

2. The browser redirects the user automatically via an HTTP Redirect. (See the comment from @hmac below regarding redirects)

It does however, get called when you you click on a link inside a webpage inside the webview. IIRC the twitter authorization uses an HTTP Redirect.. Bummer, this would be helpful if it worked how all the tutorials say it does. I think this is from a very old version the Android API...

You might want to consider overriding the onProgressChanged method of a WebChromeClient like here: How to listen for a WebView finishing loading a URL? or the onPageFinished() method of the WebViewClient.

回答2:

I've found what I think is a reasonable way to do this thanks to the previous answer and comments pointing me in the right direction.

What I did is override onPageStarted and onPageFinished in a custom WebViewClient. The code goes something like this...

@Override
public void onPageStarted(WebView view, String url, Bitmap favicon) {
  if (pendingUrl == null) {
    pendingUrl = url;
  }
}

@Override
public void onPageFinished(WebView view, String url) {
  if (!url.equals(pendingUrl)) {
    Log.d(TAG, "Detected HTTP redirect " + pendingUrl + "->" + url);
    pendingUrl = null;
  }
}

And of course along with the Log.d you would put any specific code you want to run upon detecting the redirect.