有什么方法可以减小 DataColumn 的大小吗？

我在 Flutter 中使用 DataTable 类

columns: <DataColumn> [
      DataColumn(
        label: Text("Column A",
            style: Theme.of(context).textTheme.subtitle),
        numeric: false,
        onSort: (i, b) {},
        tooltip: "Perticulars",
      ),
      DataColumn(
        label: Text("Column B",
            style: Theme.of(context).textTheme.subtitle),
        numeric: false,
        onSort: (i, b) {},
        tooltip: "As per Assessee",
      ),
      DataColumn(
        label:
            Text("Column C", style: Theme.of(context).textTheme.subtitle),
        numeric: false,
        onSort: (i, b) {},
        tooltip: "As per ITD",
      )
    ],

最佳答案

我删除了一些关于排序的代码。您可以更改 _tablePadding 和 _columnSpacing 以减小大小:

import 'dart:math' as math;
import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';

class CustomDataTable extends DataTable {
  CustomDataTable({
    Key key,
    @required this.columns,
    this.sortColumnIndex,
    this.sortAscending = true,
    this.onSelectAll,
    @required this.rows,
  }) :
  assert(columns != null),
       assert(columns.isNotEmpty),
       assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length)),
       assert(sortAscending != null),
       assert(rows != null),
       assert(!rows.any((DataRow row) => row.cells.length != columns.length)),
             _onlyTextColumn = _initOnlyTextColumn(columns),
  super(
            key: key,
            columns: columns,
            sortColumnIndex: sortColumnIndex,
            sortAscending: sortAscending,
            onSelectAll: onSelectAll,
            rows: rows);

  final List<DataColumn> columns;
  final int sortColumnIndex;
  final bool sortAscending;
  final ValueSetter<bool> onSelectAll;
  final List<DataRow> rows;


  static const double _headingRowHeight = 56.0;
  static const double _dataRowHeight = 48.0;
  static const double _tablePadding = 18.0;
  static const double _columnSpacing = 56.0;
  static const double _headingFontSize = 12.0;
  static const Duration _sortArrowAnimationDuration = Duration(milliseconds: 150);
  static const Color _grey100Opacity = Color(0x0A000000); // Grey 100 as opacity instead of solid color
  static const Color _grey300Opacity = Color(0x1E000000); // Dark theme variant is just a guess.

  final int _onlyTextColumn;
  static int _initOnlyTextColumn(List<DataColumn> columns) {
    int result;
    for (int index = 0; index < columns.length; index += 1) {
      final DataColumn column = columns[index];
      if (!column.numeric) {
        if (result != null)
          return null;
        result = index;
      }
    }
    return result;
  }

  bool get _debugInteractive {
    return columns.any((DataColumn column) => false)
        || rows.any((DataRow row) => false);
  }

  static final LocalKey _headingRowKey = UniqueKey();

  void _handleSelectAll(bool checked) {
    if (onSelectAll != null) {
      onSelectAll(checked);
    } else {
      for (DataRow row in rows) {
        if ((row.onSelectChanged != null) && (row.selected != checked))
          row.onSelectChanged(checked);
      }
    }
  }


  Widget _buildCheckbox({
    Color color,
    bool checked,
    VoidCallback onRowTap,
    ValueChanged<bool> onCheckboxChanged,
  }) {
    Widget contents = Semantics(
      container: true,
      child: Padding(
        padding: const EdgeInsetsDirectional.only(start: _tablePadding, end: _tablePadding / 2.0),
        child: Center(
          child: Checkbox(
            activeColor: color,
            value: checked,
            onChanged: onCheckboxChanged,
          ),
        ),
      ),
    );
    if (onRowTap != null) {
      contents = TableRowInkWell(
        onTap: onRowTap,
        child: contents,
      );
    }
    return TableCell(
      verticalAlignment: TableCellVerticalAlignment.fill,
      child: contents,
    );
  }

  Widget _buildHeadingCell({
    BuildContext context,
    EdgeInsetsGeometry padding,
    Widget label,
    String tooltip,
    bool numeric,
    VoidCallback onSort,
    bool sorted,
    bool ascending,
  }) {
    label = Container(
      padding: padding,
      height: _headingRowHeight,
      alignment: numeric ? Alignment.centerRight : AlignmentDirectional.centerStart,
      child: AnimatedDefaultTextStyle(
        style: TextStyle(
          // TODO(ianh): font family should match Theme; see https://github.com/flutter/flutter/issues/3116
          fontWeight: FontWeight.w500,
          fontSize: _headingFontSize,
          height: math.min(1.0, _headingRowHeight / _headingFontSize),
          color: (Theme.of(context).brightness == Brightness.light)
              ? ((onSort != null && sorted) ? Colors.black87 : Colors.black54)
              : ((onSort != null && sorted) ? Colors.white : Colors.white70),
        ),
        softWrap: false,
        duration: _sortArrowAnimationDuration,
        child: label,
      ),
    );
    if (tooltip != null) {
      label = Tooltip(
        message: tooltip,
        child: label,
      );
    }
    if (onSort != null) {
      label = InkWell(
        onTap: onSort,
        child: label,
      );
    }
    return label;
  }

  Widget _buildDataCell({
    BuildContext context,
    EdgeInsetsGeometry padding,
    Widget label,
    bool numeric,
    bool placeholder,
    bool showEditIcon,
    VoidCallback onTap,
    VoidCallback onSelectChanged,
  }) {
    final bool isLightTheme = Theme.of(context).brightness == Brightness.light;
    if (showEditIcon) {
      const Widget icon = Icon(Icons.edit, size: 18.0);
      label = Expanded(child: label);
      label = Row(
        textDirection: numeric ? TextDirection.rtl : null,
        children: <Widget>[ label, icon ],
      );
    }
    label = Container(
      padding: padding,
      height: _dataRowHeight,
      alignment: numeric ? Alignment.centerRight : AlignmentDirectional.centerStart,
      child: DefaultTextStyle(
        style: TextStyle(
          // TODO(ianh): font family should be Roboto; see https://github.com/flutter/flutter/issues/3116
          fontSize: 13.0,
          color: isLightTheme
              ? (placeholder ? Colors.black38 : Colors.black87)
              : (placeholder ? Colors.white30 : Colors.white70),
        ),
        child: IconTheme.merge(
          data: IconThemeData(
            color: isLightTheme ? Colors.black54 : Colors.white70,
          ),
          child: DropdownButtonHideUnderline(child: label),
        ),
      ),
    );
    if (onTap != null) {
      label = InkWell(
        onTap: onTap,
        child: label,
      );
    } else if (onSelectChanged != null) {
      label = TableRowInkWell(
        onTap: onSelectChanged,
        child: label,
      );
    }
    return label;
  }


  @override
  Widget build(BuildContext context) {
    assert(!_debugInteractive || debugCheckHasMaterial(context));

    final ThemeData theme = Theme.of(context);
    final BoxDecoration _kSelectedDecoration = BoxDecoration(
      border: Border(bottom: Divider.createBorderSide(context, width: 1.0)),
      // The backgroundColor has to be transparent so you can see the ink on the material
      color: (Theme.of(context).brightness == Brightness.light) ? _grey100Opacity : _grey300Opacity,
    );
    final BoxDecoration _kUnselectedDecoration = BoxDecoration(
      border: Border(bottom: Divider.createBorderSide(context, width: 1.0)),
    );

    final bool showCheckboxColumn = rows.any((DataRow row) => row.onSelectChanged != null);
    final bool allChecked = showCheckboxColumn && !rows.any((DataRow row) => row.onSelectChanged != null && !row.selected);

    final List<TableColumnWidth> tableColumns = List<TableColumnWidth>(columns.length + (showCheckboxColumn ? 1 : 0));
    final List<TableRow> tableRows = List<TableRow>.generate(
      rows.length + 1, // the +1 is for the header row
          (int index) {
        return TableRow(
          key: index == 0 ? _headingRowKey : rows[index - 1].key,
          decoration: index > 0 && rows[index - 1].selected ? _kSelectedDecoration
              : _kUnselectedDecoration,
          children: List<Widget>(tableColumns.length),
        );
      },
    );

    int rowIndex;

    int displayColumnIndex = 0;
    if (showCheckboxColumn) {
      tableColumns[0] = const FixedColumnWidth(_tablePadding + Checkbox.width + _tablePadding / 2.0);
      tableRows[0].children[0] = _buildCheckbox(
        color: theme.accentColor,
        checked: allChecked,
        onCheckboxChanged: _handleSelectAll,
      );
      rowIndex = 1;
      for (DataRow row in rows) {
        tableRows[rowIndex].children[0] = _buildCheckbox(
          color: theme.accentColor,
          checked: row.selected,
          onRowTap: () => row.onSelectChanged != null ? row.onSelectChanged(!row.selected) : null ,
          onCheckboxChanged: row.onSelectChanged,
        );
        rowIndex += 1;
      }
      displayColumnIndex += 1;
    }

    for (int dataColumnIndex = 0; dataColumnIndex < columns.length; dataColumnIndex += 1) {
      final DataColumn column = columns[dataColumnIndex];
      final EdgeInsetsDirectional padding = EdgeInsetsDirectional.only(
        start: dataColumnIndex == 0 ? showCheckboxColumn ? _tablePadding / 2.0 : _tablePadding : _columnSpacing / 2.0,
        end: dataColumnIndex == columns.length - 1 ? _tablePadding : _columnSpacing / 2.0,
      );
      if (dataColumnIndex == _onlyTextColumn) {
        tableColumns[displayColumnIndex] = const IntrinsicColumnWidth(flex: 1.0);
      } else {
        tableColumns[displayColumnIndex] = const IntrinsicColumnWidth();
      }
      tableRows[0].children[displayColumnIndex] = _buildHeadingCell(
        context: context,
        padding: padding,
        label: column.label,
        tooltip: column.tooltip,
        numeric: column.numeric,
        onSort: () => column.onSort != null ? column.onSort(dataColumnIndex, sortColumnIndex == dataColumnIndex ? !sortAscending : true) : null,
        sorted: dataColumnIndex == sortColumnIndex,
        ascending: sortAscending,
      );
      rowIndex = 1;
      for (DataRow row in rows) {
        final DataCell cell = row.cells[dataColumnIndex];
        tableRows[rowIndex].children[displayColumnIndex] = _buildDataCell(
          context: context,
          padding: padding,
          label: cell.child,
          numeric: column.numeric,
          placeholder: cell.placeholder,
          showEditIcon: cell.showEditIcon,
          onTap: cell.onTap,
          onSelectChanged: () => row.onSelectChanged != null ? row.onSelectChanged(!row.selected) : null,
        );
        rowIndex += 1;
      }
      displayColumnIndex += 1;
    }

    return Table(
      columnWidths: tableColumns.asMap(),
      children: tableRows,
    );
  }
}

关于datatable - Flutter:有没有办法在 "fix size"中获取 DataColumn 的/"reduce size" "DataTable"？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55417944/