SwipeListener for android From http://stackoverflow.com/questions/13095494/how-to-detect-swipe-direction-between-left-right-and-up-down

OnSwipeListener.java

public class OnSwipeListener extends GestureDetector.SimpleOnGestureListener{

@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {

    // Grab two events located on the plane at e1=(x1, y1) and e2=(x2, y2)
    // Let e1 be the initial event
    // e2 can be located at 4 different positions, consider the following diagram
    // (Assume that lines are separated by 90 degrees.)
    //
    //
    //         \ A  /
    //          \  /
    //       D   e1   B
    //          /  \
    //         / C  \
    //
    // So if (x2,y2) falls in region:
    //  A => it's an UP swipe
    //  B => it's a RIGHT swipe
    //  C => it's a DOWN swipe
    //  D => it's a LEFT swipe
    //

    float x1 = e1.getX();
    float y1 = e1.getY();

    float x2 = e2.getX();
    float y2 = e2.getY();

    Direction direction = getDirection(x1,y1,x2,y2);
    return onSwipe(direction);
}

public boolean onSwipe(Direction direction){
    return false;
}

/**
 * Given two points in the plane p1=(x1, x2) and p2=(y1, y1), this method
 * returns the direction that an arrow pointing from p1 to p2 would have.
 * @param x1 the x position of the first point
 * @param y1 the y position of the first point
 * @param x2 the x position of the second point
 * @param y2 the y position of the second point
 * @return the direction
 */
public Direction getDirection(float x1, float y1, float x2, float y2){
    double angle = getAngle(x1, y1, x2, y2);
    return Direction.get(angle);
}

/**
 *
 * Finds the angle between two points in the plane (x1,y1) and (x2, y2)
 * The angle is measured with 0/360 being the X-axis to the right, angles
 * increase counter clockwise.
 *
 * @param x1 the x position of the first point
 * @param y1 the y position of the first point
 * @param x2 the x position of the second point
 * @param y2 the y position of the second point
 * @return the angle between two points
 */
public double getAngle(float x1, float y1, float x2, float y2) {

    double rad = Math.atan2(y1-y2,x2-x1) + Math.PI;
    return (rad*180/Math.PI + 180)%360;
}


public enum Direction{
    up,
    down,
    left,
    right;

    /**
     * Returns a direction given an angle.
     * Directions are defined as follows:
     *
     * Up: [45, 135]
     * Right: [0,45] and [315, 360]
     * Down: [225, 315]
     * Left: [135, 225]
     *
     * @param angle an angle from 0 to 360 - e
     * @return the direction of an angle
     */
    public static Direction get(double angle){
        if(inRange(angle, 45, 135)){
            return Direction.up;
        }
        else if(inRange(angle, 0,45) || inRange(angle, 315, 360)){
            return Direction.right;
        }
        else if(inRange(angle, 225, 315)){
            return Direction.down;
        }
        else{
            return Direction.left;
        }

    }

    /**
     * @param angle an angle
     * @param init the initial bound
     * @param end the final bound
     * @return returns true if the given angle is in the interval [init, end).
     */
    private static boolean inRange(double angle, float init, float end){
        return (angle >= init) && (angle < end);
    }
}
}