Вот решение:
webView.setWebViewClient( new WebViewClient() {
@Override
public void onPageStarted( WebView view, String url, Bitmap favicon ) {
super.onPageStarted( webView, url, favicon );
progressBar.setVisibility( View.VISIBLE );
}
@Override
public void onPageFinished( WebView view, String url ) {
super.onPageFinished( webView, url );
progressBar.setVisibility( View.INVISIBLE );
previousButton.setEnabled( view.canGoBack() );
nextButton.setEnabled( view.canGoForward() );
}
@Override
public void onReceivedError( WebView view, int errorCode, String description, String failingUrl ) {
super.onReceivedError( webView, errorCode, description, failingUrl );
Toast.makeText( BrowserActivity.this, description, Toast.LENGTH_LONG );
}
} );