Swipe Detection

@Override
public boolean onTouchEvent(MotionEvent event)
{     
    switch(event.getAction())
    {
      case MotionEvent.ACTION_DOWN:
          x1 = event.getX();  
          y1 = event.getY();
      break;   
      
      case MotionEvent.ACTION_UP:
          x2 = event.getX();
          y2 = event.getY();
          
          float deltaX = x2 - x1;
          float deltaY = y2 - y1;

          // Left / Right
          if (Math.abs(deltaX) > MIN_DISTANCE) 
          {
              // Left to Right swipe action
              if (x2 > x1)
              {
                  Toast.makeText(this, "Left to Right swipe [Next]", Toast.LENGTH_SHORT).show ();                     
              }

              // Right to left swipe action               
              else 
              {
                  Toast.makeText(this, "Right to Left swipe [Previous]", Toast.LENGTH_SHORT).show ();                    
              }

          } else {
              // consider as something else - a screen tap for example
          } 
          
          // Up / Down
          if (Math.abs(deltaY) > MIN_DISTANCE) 
          {
              // Top to Bottom, (INVERSE IF REVERSED)
              if (y2 > y1)
              {
                  Toast.makeText(this, "Top to Bottom swipe [Next]", Toast.LENGTH_SHORT).show ();                     
              }

              // Bottom to Top               
              else {
                  Toast.makeText(this, "Bottom to Top swipe [Previous]", Toast.LENGTH_SHORT).show ();                    
              }

          } else {
              // consider as something else - a screen tap for example
          }       
      break;   
    }           
    return super.onTouchEvent(event);       
}

Might need to reverse the logic on line:40 if the UP / DOWN is reversed.