build method

@override Widget build(BuildContext context)

Builds the transition, uses either buildVerticalTransition, buildDefaultTransition, or buildBidirectionalTransition depending on useVerticalTransition.

This method is only responsible for building the animations that all the transitions use.

Implementation

@override
Widget build(BuildContext context) {
  // Define at which point during the transition the scrim will start to
  // show.
  final scrimAnimationStart = useVerticalTransition
      ? 0.0
      : transitionWidget != null
          ? 0.0
          : 0.2;

  // Define the scrim animation.
  final Animation<Color?> scrimAnimation = ColorTween(
    begin: settings.scrimColor.withOpacity(0.0),
    end: settings.scrimColor,
  ).animate(CurvedAnimation(
    parent: animation,
    curve: Interval(
      scrimAnimationStart,
      1.0,
      curve: Curves.fastOutSlowIn,
    ),
    reverseCurve: Interval(
      scrimAnimationStart,
      1.0,
      curve: Curves.fastOutSlowIn.flipped,
    ),
  ));

  if (renderBox == null) {
    return buildDefaultTransition();
  }

  final transitionColor =
      settings.transitionColor ?? Theme.of(context).colorScheme.surface;

  // Return the animated scrim with the appropriate transition as child.
  return Container(
    color: scrimAnimation.value,
    child: LayoutBuilder(
      builder: (context, constraints) => FadeTransition(
        opacity: parentToChildAnimation,
        child: Stack(
          children: <Widget>[
            // Animate the position of the child screen from the origin of
            // [renderBox] to fill the entire screen.
            PositionedTransition(
              rect:
                  positionTween(constraints).animate(positionAnimationCurve),
              child: AnimatedBuilder(
                animation: positionAnimationCurve,
                child: OverflowBox(
                  alignment: Alignment.topCenter,
                  minWidth: constraints.maxWidth,
                  maxWidth: constraints.maxWidth,
                  minHeight: constraints.maxHeight,
                  maxHeight: constraints.maxHeight,
                  child: child,
                ),
                builder: (context, child) => ClipRRect(
                  borderRadius: borderRadius.evaluate(positionAnimationCurve),
                  clipBehavior: Clip.antiAlias,
                  child: Stack(
                    children: <Widget>[
                      Container(
                        width: double.infinity,
                        height: double.infinity,
                        color: transitionColor,
                      ),
                      settings.transitionToChild
                          ? useVerticalTransition
                              ? buildVerticalTransition(child!)
                              : buildBidirectionalTransition(child!)
                          : child!,
                    ],
                  ),
                ),
              ),
            ),
          ],
        ),
      ),
    ),
  );
}