Responding to touch interaction

People have become used to interacting with a device by tapping and swiping on a touchscreen. In this recipe, we'll take a look at how you can detect when a user is touching the screen, and let your sketch respond to that interaction. We'll make a simple drawing application to see how it's done.

How to do it...

We'll start by writing the setup() function and declare a boolean variable. If the value of this variable is true, we'll draw some things on the screen.

boolean touching = false;
  
void setup()
{
  size( displayWidth, displayHeight );
  smooth();
  
  background( 0 );
}

To respond to a user touching the screen, we'll override the surfaceTouchevent() method. If we detect a touch we'll set the touching variable to true:

public boolean surfaceTouchEvent( MotionEvent event )
{
  if ( event.getAction() == 2 ) {
    touching = true;
  } else {
    touching = false;
  }
    
  return super.surfaceTouchEvent( event );
}

In the draw() function, we'll add the mouseX...