Question

With reference to this WebView tutorial, in particular this method

private void setupWebView(){
    String MAP_URL = "http://gmaps-samples.googlecode.com/svn/trunk/articles-android-webmap/simple-android-map.html";
    String centerURL = "javascript:centerAt(" + mostRecentLocation.getLatitude() + ","+ mostRecentLocation.getLongitude()+ ")";
    webView = (WebView) findViewById(R.id.webview);
    webView.getSettings().setJavaScriptEnabled(true);
    //Wait for the page to load then send the location information
    webView.setWebViewClient(new WebViewClient(){
        @Override
        public void onPageFinished(WebView view, String url){
            webView.loadUrl(centerURL);
        }
    });
    webView.loadUrl(MAP_URL);
}

I’ve noticed that if I place the webView.loadUrl(centerURL); directly after
webView.loadUrl(MAP_URL); like this

private void setupWebView(){
    String MAP_URL = "http://gmaps-samples.googlecode.com/svn/trunk/articles-android-webmap/simple-android-map.html";
    String centerURL = "javascript:centerAt(" + mostRecentLocation.getLatitude() + "," + mostRecentLocation.getLongitude()+ ")";
    webView = (WebView) findViewById(R.id.webview);
    webView.getSettings().setJavaScriptEnabled(true);
    //Wait for the page to load then send the location information
    webView.setWebViewClient(new WebViewClient(){
        @Override
        public void onPageFinished(WebView view, String url){
            //DO NOTHING
        }
    });
    webView.loadUrl(MAP_URL);
    webView.loadUrl(centerURL);
}

it no longer works. So the centreAt(..) javascript method is contained int the MAP_URL.

I’m wondering if the webView.loadUrl(..) method returns before the url has actually been loaded.
It looks that way since the top method waits for it to load fully before running the javascript

Answer 1

Yes, webView.loadUrl() is asynchronous: it returns immediately and WebView keeps working in it’s own thread.

To monitor WebView page loading use WebViewClient.onPageFinished(..):

webview.setWebViewClient(new WebViewClient() {
    public void onPageFinished(WebView view, String url) {
        // do something here
    }
});