update method

void update(double dt)

Implementation

void update(double dt) {
  if (_dragPosition == null ||
      _rectBackgroundDirection == null ||
      _rect == null) return;
  if (_dragging) {
    double radAngle = atan2(
      _dragPosition!.dy - _rectBackgroundDirection!.center.dy,
      _dragPosition!.dx - _rectBackgroundDirection!.center.dx,
    );

    // Distance between the center of joystick background & drag position
    Vector2 centerPosition = _rectBackgroundDirection!.center.toVector2();
    Vector2 dragPosition = _dragPosition!.toVector2();
    double dist = centerPosition.distanceTo(dragPosition);

    // The maximum distance for the knob position the edge of
    // the background + half of its own size. The knob can wander in the
    // background image, but not outside.
    dist = min(dist, _tileSize);

    // Calculation the knob position
    double nextX = dist * cos(radAngle);
    double nextY = dist * sin(radAngle);
    Offset nextPoint = Offset(nextX, nextY);

    Offset diff = Offset(
          _rectBackgroundDirection!.center.dx + nextPoint.dx,
          _rectBackgroundDirection!.center.dy + nextPoint.dy,
        ) -
        _rect!.center;
    _rect = _rect!.shift(diff);

    double intensity = dist / _tileSize;

    _controller.onJoystickAction(
      JoystickActionEvent(
        id: actionId,
        event: ActionEvent.MOVE,
        intensity: intensity,
        radAngle: radAngle,
      ),
    );
  } else {
    Offset diff = _dragPosition! - _rect!.center;
    _rect = _rect!.shift(diff);
  }
}