Initializing the butShareScreen, and adding a click listener.

initElementsOnScreen.java

 // Share screen button
   butShareScreen = (Button) findViewById(R.id.butShareScreen);
   butShareScreen.setOnClickListener(
           new View.OnClickListener() {
               @Override
               public void onClick(View v) {
                   // Run this method when this button is clicked
                   startScreenShare();
               }
           });