How do I make a cell bold in Dart?

Assign a CellStyle with bold set to true, either through the cellStyle argument of updateCell or by setting cell.cellStyle directly.

How to style Excel cells in Dart

Fonts, colours, fills, borders and alignment, applied through a single CellStyle.

Install#

dart pub add excel_plus

import 'package:excel_plus/excel_plus.dart';

Font, colour, fill and alignment#

sheet.updateCell(
  CellIndex.indexByString('A1'),
  TextCellValue('Header'),
  cellStyle: CellStyle(
    bold: true,
    italic: true,
    fontSize: 14,
    fontColorHex: ExcelColor.white,
    backgroundColorHex: ExcelColor.fromHexString('#21A366'),
    horizontalAlign: HorizontalAlign.Center,
    verticalAlign: VerticalAlign.Center,
  ),
);

You can also assign a style to a cell that already holds a value:

sheet.cell(CellIndex.indexByString('A1')).cellStyle = CellStyle(bold: true);

Colours#

Use a named colour or any hex string. Theme and indexed colours are supported too, which matters when a workbook should follow the theme it was created with.

ExcelColor.red;
ExcelColor.fromHexString('#21A366');
ExcelColor.theme(ThemeColor.accent1);
ExcelColor.indexed(12);

Borders#

sheet.cell(CellIndex.indexByString('A1')).cellStyle = CellStyle(
  leftBorder: Border(borderStyle: BorderStyle.Thin),
  rightBorder: Border(borderStyle: BorderStyle.Thin),
  topBorder: Border(borderStyle: BorderStyle.Medium),
  bottomBorder: Border(borderStyle: BorderStyle.Medium, borderColorHex: ExcelColor.red),
);

Gradient fills#

// Linear, sweeping top to bottom. 0 degrees runs left to right.
sheet.cell(CellIndex.indexByString('A1')).cellStyle = CellStyle(
  gradientFill: GradientFill.linear(
    degree: 90,
    stops: [
      GradientStop(0, ExcelColor.fromHexString('#2962FF')),
      GradientStop(1, ExcelColor.white),
    ],
  ),
);

// Path, radiating from the centre outwards.
sheet.cell(CellIndex.indexByString('A2')).cellStyle = CellStyle(
  gradientFill: GradientFill.path(
    left: 0.5, right: 0.5, top: 0.5, bottom: 0.5,
    stops: [GradientStop(0, ExcelColor.white), GradientStop(1, ExcelColor.red)],
  ),
);

Wrapping and rotation#

CellStyle(
  textWrapping: TextWrapping.WrapText,
  rotation: 45,
);

Reusing one style#

Build the style once and apply it across a header row rather than constructing a new one per cell.

final header = CellStyle(
  bold: true,
  fontColorHex: ExcelColor.white,
  backgroundColorHex: ExcelColor.fromHexString('#21A366'),
  horizontalAlign: HorizontalAlign.Center,
);

for (var col = 0; col < 5; col++) {
  sheet.cell(CellIndex.indexByColumnRow(columnIndex: col, rowIndex: 0)).cellStyle = header;
}