README.md

How-to-maintain-selected-rows-while-changing-the-page-in-the-Flutter-DataPager-SfDataGrid-

The Syncfusion Flutter DataTable supports maintaining the selected rows collection within a page. While navigating to another page, the previously selected rows are not maintained.

You can maintain the internal collection to hold the selected data with the page index in the onPageNavigationStart callback. Then, you should add those selected rows of the navigated page to the DataGridController.selectedRows property in the onPageNavigationEnd callback so that you can maintain the selection even after navigation.

The following steps explain how to maintain selected rows while changing the page in the Flutter DataPager:

STEP 1:

Create a data source class by extending DataGridSource for mapping data to the SfDataGrid.

class EmployeeDataSource extends DataGridSource {
  EmployeeDataSource(List<Employee> employees) {
    buildDataGridRow(employees);
  }

  void buildDataGridRow(List<Employee> employeeData) {
    dataGridRow = employeeData.map<DataGridRow>((employee) {
      return DataGridRow(cells: [
        DataGridCell<int>(columnName: 'id', value: employee.id),
        DataGridCell<String>(columnName: 'name', value: employee.name),
        DataGridCell<String>(
            columnName: 'designation', value: employee.designation),
        DataGridCell<int>(columnName: 'salary', value: employee.salary),
      ]);
    }).toList();
  }

  List<DataGridRow> dataGridRow = <DataGridRow>[];

  @override
  List<DataGridRow> get rows => dataGridRow.isEmpty ? [] : dataGridRow;

  @override
  DataGridRowAdapter? buildRow(DataGridRow row) {
    return DataGridRowAdapter(
        cells: row.getCells().map<Widget>((dataGridCell) {
      return Container(
          alignment: Alignment.center,
          padding: const EdgeInsets.symmetric(horizontal: 8.0),
          child: Text(
            dataGridCell.value.toString(),
            overflow: TextOverflow.ellipsis,
          ));
    }).toList());
  }
}

STEP 2:

Create a new SfDataPager widget, and set the SfDataGrid.DataGridSource to the SfDataPager.Delegate property.

Set the number of pages required to display in the DataPager to the pageCount property. Maintain the selected rows in the internal collection selectedRowsCollection. In the onPageNavigationStart callback, add the desired rows based on the current page, and in the onPageNavigationEnd callback, assign the selected rows for the current page from a collection.

  Map<String, List<DataGridRow>> selectedRowsCollection = {};

  Widget _buildDataPager() {
    return SfDataPager(
        pageCount: ((_employees.length / _rowsPerPage).ceil()).toDouble(),
        direction: Axis.horizontal,
        delegate: _employeeDataSource,
        controller: _dataPagerController,
        onPageNavigationStart: (int pageIndex) {
          selectedRowsCollection[_dataPagerController.selectedPageIndex
              .toString()] = _dataGridController.selectedRows.toList();
        },
        onPageNavigationEnd: (int pageIndex) {
          if (selectedRowsCollection.containsKey('$pageIndex') &&
              selectedRowsCollection['$pageIndex'] != null &&
              selectedRowsCollection['$pageIndex']!.isNotEmpty) {
            _dataGridController.selectedRows =
                selectedRowsCollection['$pageIndex']!;
          }
        });
  }

STEP 3:

Initialize the SfDataGrid widget with all the required properties. SfDataPager can placed above or below based on the requirement of managing the easy data paging.

Wrap the SfDataGrid and SfDataPager inside the SizedBox.

Here we are placed the SfDataPager below of the SfDataGrid inside a Column widget.

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(title: const Text('Syncfusion DataPager')),
        body: LayoutBuilder(builder: (context, constraints) {
          return Column(children: [
            SizedBox(
                height: constraints.maxHeight - _dataPagerHeight,
                child: SfDataGrid(
                    source: _employeeDataSource,
                    controller: _dataGridController,
                    selectionMode: SelectionMode.multiple,
                    navigationMode: GridNavigationMode.row,
                    columnWidthMode: ColumnWidthMode.fill,
                    columns: <GridColumn>[
                      GridColumn(
                          columnName: 'id',
                          label: Container(
                              padding:
                                  const EdgeInsets.symmetric(horizontal: 8.0),
                              alignment: Alignment.center,
                              child: const Text('ID',
                                  overflow: TextOverflow.ellipsis))),
                      GridColumn(
                          columnName: 'name',
                          label: Container(
                              padding:
                                  const EdgeInsets.symmetric(horizontal: 8.0),
                              alignment: Alignment.center,
                              child: const Text('Name',
                                  overflow: TextOverflow.ellipsis))),
                      GridColumn(
                          columnName: 'designation',
                          label: Container(
                              padding:
                                  const EdgeInsets.symmetric(horizontal: 8.0),
                              alignment: Alignment.center,
                              child: const Text('Designation',
                                  overflow: TextOverflow.ellipsis))),
                      GridColumn(
                          columnName: 'salary',
                          label: Container(
                              padding:
                                  const EdgeInsets.symmetric(horizontal: 8.0),
                              alignment: Alignment.center,
                              child: const Text('Salary',
                                  overflow: TextOverflow.ellipsis))),
                    ])),
            SizedBox(height: 60, child: _buildDataPager())
          ]);
        }));
  }