title: Detect if a specific button has been clicked in Android WebView
body: <p>I am currently working on an android app. This app consists of a WebView and displays a website which I don't own. (F.e. a WebStore) </p>
  
  <p>The app is supposed to recognize/detect when a user clicks a specific button on this website (f.e a "Buy Product" button). If a user clicks such a button, then the app makes a toast pop up.</p>
  
  <p>I know this will be different for every website, however how would I program the click detection in general? I read a few articles about injecting JavaScript etc, however I dont really understand how this is supposed to work. Is there a way to say: If a user clicks on the button with id=buy_button, then show toast?</p>
  
  <p>Thanks for your help!</p>