animatedBuilder method

Implementation

@override
Widget animatedBuilder(BuildContext context, Widget? child) {
  /// Output of CurveTween is in the range [0, 1] for majority of the curves.
  /// It is converted to [0, textCharacters.length + extraLengthForBlinks].
  final textLen = textCharacters.length;
  final typewriterValue = (_typewriterText.value.clamp(0, 1) *
          (textCharacters.length + extraLengthForBlinks))
      .round();

  var showCursor = true;
  var visibleString = text;
  if (typewriterValue == 0) {
    visibleString = '';
    showCursor = false;
  } else if (typewriterValue > textLen) {
    showCursor = (typewriterValue - textLen) % 2 == 0;
  } else {
    visibleString = textCharacters.take(typewriterValue).toString();
  }

  return RichText(
    text: TextSpan(
      children: [
        TextSpan(text: visibleString),
        TextSpan(
          text: cursor,
          style:
              showCursor ? null : const TextStyle(color: Colors.transparent),
        )
      ],
      style: DefaultTextStyle.of(context).style.merge(textStyle),
    ),
    textAlign: textAlign,
  );
}