lexanderA » WebChromeClient

Adding alert() support to a WebView

Aleksander Kmetec — Tue, 27 Jan 2009 20:54:09 +0000

As promised earlier, here is an example of how to add support for alert() function to a WebView in your Android application:


final WebView browser = (WebView)findViewById(R.id.browser);
/* JavaScript must be enabled if you want it to work, obviously */
browser.getSettings().setJavaScriptEnabled(true);

final Context myApp = this;

/* WebChromeClient must be set BEFORE calling loadUrl! */
browser.setWebChromeClient(new WebChromeClient() {
    @Override
    public boolean onJsAlert(WebView view, String url, String message, final android.webkit.JsResult result)
    {
        new AlertDialog.Builder(myApp)
            .setTitle("javaScript dialog")
            .setMessage(message)
            .setPositiveButton(android.R.string.ok,
                    new AlertDialog.OnClickListener()
                    {
                        public void onClick(DialogInterface dialog, int which)
                        {
                            result.confirm();
                        }
                    })
            .setCancelable(false)
            .create()
            .show();

        return true;
    };
});

/* load a web page which uses the alert() function */
browser.loadUrl("http://lexandera.com/files/jsexamples/alert.html");

Code for adding support for confirm() and prompt() is almost identical and can be found in Mosembro’s source code.

Android WebChromeClient

Aleksander Kmetec — Tue, 20 Jan 2009 03:30:16 +0000

My blog stats are telling me that many visitors are arriving here looking for examples on how to implement WebChromeClient on Android. I don’t (yet) have a nice article about how to do it, but you can have a look at how I implemented WebChromeClient in Mosembro, if you came here for that reason. Just use your browser’s search functionality and look for “new WebChromeClient”.

Injecting JavaScript into a WebView

Aleksander Kmetec — Fri, 02 Jan 2009 06:05:21 +0000

Back in early ‘08, while the Androd developer challenge was in full swing, a fairly common question which went without a satisfactory answer was: “How can I manipulate the contents of a WebView?”. I now finally have the answer, thanks to a couple of lines of code I stumbled upon while looking at the source of Jeffrey Sharkey’s OilCan.

The solution is actually very simple: wait for the original page to finish loading, then inject your own JavaScript code into it by calling webview.loadUrl(“javascript:your-code-here”) when your webvew’s onPageFinished() event is triggered. Loading an URL beginning with “javascript:” is the exact same approach used by bookmarklets.

Here’s a simple example which loads a page and then sets its text color to red:


final WebView webview = (WebView)findViewById(R.id.browser);
/* JavaScript must be enabled if you want it to work, obviously */
webview.getSettings().setJavaScriptEnabled(true);

/* WebViewClient must be set BEFORE calling loadUrl! */
webview.setWebViewClient(new WebViewClient() {
    @Override
    public void onPageFinished(WebView view, String url)
    {
        webview.loadUrl("javascript:(function() { " +
                "document.getElementsByTagName('body')[0].style.color = 'red'; " +
                "})()");
    }
});

webview.loadUrl("http://code.google.com/android");

That’s it.

Please note though that alert() and confirm() JavaScript functions will not work unless you also register a WebChromeClient which implements the required methods.