title: How to create change listener for variable?
body: <p>Let's say I have some variable defined using the statement<code>int someVariable;</code>. While the code runs, the variable's value changes.</p>
  
  <p>How can I track the changes in this variable?  How could I implement some Listener that behaves like onSomeVariableChangedListener? </p>
  
  <p>I also need to know when some other method in one page has been executed so I can set a Listener in another class.</p>