Android: How to check for successful load of url when using webview.loadUrl

Question

In webview android I am trying to load a url and in order to check if the load of this url is done successfully (internet connection was available, the server was up etc) I was under the impression that webview.loadUrl would throw exceptions, but wrong! as it explicitly is stated in here "an exception will NOT be thrown".

So how can I check to see if webview.loadUrl did not fail ?

Answer 1

Unfortunately, currently there is no easy way in WebView to ensure that everything on the page has been loaded successfully. We are hoping for a better API to come up in future version. Let me explain what you can do now.

First of all, in order to detect any problems that prevent WebView from making a connection to the server for loading your main page (e.g. bad domain name, I/O error, etc.), you should use WebViewClient.onReceivedError callback as other people correctly suggest:

public class MyWebViewClient extends WebViewClient {
    @Override
    public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
        // Make a note about the failed load.
    }
}
myWebView.setWebViewClient(new MyWebViewClient());

If the server connection was successful, and the main page was retrieved and parsed, you will receive WebView.onPageFinished callback, so you also need to have this in your WebViewClient subclass:

public class MyWebViewClient extends WebViewClient {
    ...
    @Override
    public void onPageFinished(WebView view, String url) {
        // Make a note that the page has finished loading.
    }
    ...
}

The caveat here is that if you have received an HTTP error from the server (e.g. a 404 or a 500 error), this callback will be called anyway, it's just the content that you will get in your WebView will be a server error page. People suggest different ways of how to deal with it, see the answers here: How can I check from Android WebView if a page is a "404 page not found"? Basically, it really depends on what you expect to be a "good" page and a "error" page. Unfortunately, there is currently no way for the app to get the HTTP response code from WebView.

The callbacks WebViewClient.onPageStarted and WebViewClient.onProgressChanged are only useful if you want to draw a progress bar as you are loading the page.

Also note that the way of overriding WebViewClient.shouldOverrideUrlLoading that people usually suggest is not correct:

public class MyWebViewClient extends WebViewClient {
    ...
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url)         {  
        // !!! DO NOT DO THIS UNCONDITIONALLY !!!
        view.loadUrl(url);
        return true;
    }
    ...
}

What few developers realize is that the callback is also called for subframes with non-https schemes. If you'll encounter something like <iframe src='tel:1234'>, you will end up executing view.loadUrl('tel:1234') and your app will show an error page, since WebView doesn't know how to load a tel: URL. It is recommended to simply return false from the method, if you want WebView to do the loading:

public class MyWebViewClient extends WebViewClient {
    ...

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url)         {
        // Returning 'false' unconditionally is fine.
        return false;
    }
    ...
}

This doesn’t mean you should not call WebView.loadUrl from shouldOverrideUrlLoading at all. The specific pattern to avoid is doing so unconditionally for all URLs.