1. override
String toString([String prefix = '', String indentPrefix ])

Stringifies the BoxDecoration. By default, the output will be on one line. If the method is passed a non-empty string argument, then the output will span multiple lines, each prefixed by that argument.

Source 

@override
String toString([String prefix = '', String indentPrefix]) {
  List<String> result = <String>[];
  if (backgroundColor != null)
    result.add('${prefix}backgroundColor: $backgroundColor');
  if (backgroundImage != null)
    result.add('${prefix}backgroundImage: $backgroundImage');
  if (border != null)
    result.add('${prefix}border: $border');
  if (borderRadius != null)
    result.add('${prefix}borderRadius: $borderRadius');
  if (boxShadow != null) {
    if (indentPrefix != null && boxShadow.length > 1) {
      result.add('${prefix}boxShadow:');
      for (BoxShadow shadow in boxShadow)
        result.add('$indentPrefix$shadow');
    } else {
      result.add('${prefix}boxShadow: ${boxShadow.map((BoxShadow shadow) => shadow.toString()).join(", ")}');
    }
  }
  if (gradient != null)
    result.add('${prefix}gradient: $gradient');
  if (shape != BoxShape.rectangle)
    result.add('${prefix}shape: $shape');
  if (prefix == '')
    return '$runtimeType(${result.join(', ')})';
  if (result.isEmpty)
    return '$prefix<no decorations specified>';
  return result.join('\n');
}