title: why do some android events stop propagation and other don't need to?
body: <p>why do some event listeners return boolean and some don't?</p>
  
  <p>what is the meaning of <code>stopping propagation</code>?</p>
  
  <p>for instance:</p>
  
  <p><code>public void onClick(View v)</code></p>
  
  <p><code>public boolean onTouch(View v, MotionEvent event)</code></p>