Android Webview: Detect when rendering is finished

The best way to detect if a page has rendered is to use the onPageCommitVisible callback, available from API 23. onPageLoadFinished is not suitable, since it's delivered too soon (when the HTML is processed, but not yet rendered).

webview.setWebViewClient(new WebViewClient() {

    @Override
     public void onPageCommitVisible (WebView view, 
            String url)
    }

}

You should try to use a WebChromeClient and implement onProgressChanged :

http://developer.android.com/reference/android/webkit/WebChromeClient.html#onProgressChanged(android.webkit.WebView, int)

mButterflyWebView.setWebChromeClient(new WebChromeClient() {

        @Override
        public void onProgressChanged(WebView view, int progress) {
           if (progress == 100) {
               // do screenshot
           }
        }
});

EDIT : to check if onPageStarted is loaded more than once :

mButterflyWebView.setWebViewClient(new WebViewClient() {

        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) {
           Log.d("WebView", "onPageStarted " + url);
        }

        @Override
        public void onPageFinished(WebView view, String url) {
           Log.d("WebView", "onPageFinished " + url);
        }
    });