You can invoke methods and functions in your webview by using javascript url's, e.g.
webview.loadUrl("javascript:somemethod()");
You will, of course, need to enable javascript on your webview:
webview.getSettings().setJavaScriptEnabled(true);
This is from java to javascript. If you want to invoke java code / android API's from javascript, use addJavascriptInterface()
webview.addJavascriptInterface(new MyJSJavaBridge(), "api");
All of this is shown in the example url you posted as well.
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