updateColorsFile function

Future<void> updateColorsFile(File colorsFile, String backgroundColor)

Updates the colors.xml with the new adaptive launcher icon color.

Rejects values that are neither a hex color literal nor an existing file path, so we never write <color name="ic_launcher_background">assets/x.jpg</color> or <color name="ic_launcher_background">not-a-color</color> and break mergeDebugResources at build time (upstream #132).

Implementation

Future<void> updateColorsFile(File colorsFile, String backgroundColor) async {
  if (!isHexColorLiteral(backgroundColor)) {
    final asPath = File(backgroundColor);
    if (!asPath.existsSync()) {
      throw InvalidConfigException(
        "adaptive_icon_background: '$backgroundColor' is not a hex color "
        "(e.g. '#FFFFFF') and not an existing file path. Refusing to write "
        'an invalid value into colors.xml.',
      );
    }
  }
  // Write foreground color
  final List<String> lines = await colorsFile.readAsLines();
  bool foundExisting = false;
  for (int x = 0; x < lines.length; x++) {
    String line = lines[x];
    if (line.contains('name="ic_launcher_background"')) {
      foundExisting = true;
      // replace anything between tags which does not contain another tag
      line = line.replaceAll(RegExp(r'>([^><]*)<'), '>$backgroundColor<');
      lines[x] = line;
      break;
    }
  }

  // Add new line if we didn't find an existing value
  if (!foundExisting) {
    lines.insert(
      lines.length - 1,
      '\t<color name="ic_launcher_background">$backgroundColor</color>',
    );
  }

  await colorsFile.writeAsString(lines.join('\n'));
}