method animateTo

Source

Future<Null> animateTo(double target, { Duration duration, Curve curve: Curves.linear }) {
  Duration simulationDuration = duration;
  if (simulationDuration == null) {
    assert(() {
      if (this.duration == null) {
        throw new FlutterError(
          'AnimationController.animateTo() called with no explicit Duration and no default Duration.\n'
          'Either the "duration" argument to the animateTo() method should be provided, or the '
          '"duration" property should be set, either in the constructor or later, before '
          'calling the animateTo() function.'
        );
      }
      return true;
    });
    double range = upperBound - lowerBound;
    double remainingFraction = range.isFinite ? (target - _value).abs() / range : 1.0;
    simulationDuration = this.duration * remainingFraction;
  }
  stop();
  if (simulationDuration == Duration.ZERO) {
    assert(value == target);
    _status = (_direction == _AnimationDirection.forward) ?
      AnimationStatus.completed :
      AnimationStatus.dismissed;
    _checkStatusChanged();
    return new Future<Null>.value();
  }
  assert(simulationDuration > Duration.ZERO);
  assert(!isAnimating);
  return _startSimulation(new _InterpolationSimulation(_value, target, simulationDuration, curve));
}