// Copyright 2014 The Flutter Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. import 'package:flutter/foundation.dart'; import 'data_table.dart'; /// A data source for obtaining row data for [PaginatedDataTable] objects. /// /// A data table source provides two main pieces of information: /// /// * The number of rows in the data table ([rowCount]). /// * The data for each row (indexed from `0` to `rowCount - 1`). /// /// It also provides a listener API ([addListener]/[removeListener]) so that /// consumers of the data can be notified when it changes. When the data /// changes, call [notifyListeners] to send the notifications. /// /// DataTableSource objects are expected to be long-lived, not recreated with /// each build. abstract class DataTableSource extends ChangeNotifier { /// Called to obtain the data about a particular row. /// /// The [new DataRow.byIndex] constructor provides a convenient way to construct /// [DataRow] objects for this callback's purposes without having to worry about /// independently keying each row. /// /// If the given index does not correspond to a row, or if no data is yet /// available for a row, then return null. The row will be left blank and a /// loading indicator will be displayed over the table. Once data is available /// or once it is firmly established that the row index in question is beyond /// the end of the table, call [notifyListeners]. /// /// Data returned from this method must be consistent for the lifetime of the /// object. If the row count changes, then a new delegate must be provided. DataRow getRow(int index); /// Called to obtain the number of rows to tell the user are available. /// /// If [isRowCountApproximate] is false, then this must be an accurate number, /// and [getRow] must return a non-null value for all indices in the range 0 /// to one less than the row count. /// /// If [isRowCountApproximate] is true, then the user will be allowed to /// attempt to display rows up to this [rowCount], and the display will /// indicate that the count is approximate. The row count should therefore be /// greater than the actual number of rows if at all possible. /// /// If the row count changes, call [notifyListeners]. int get rowCount; /// Called to establish if [rowCount] is a precise number or might be an /// over-estimate. If this returns true (i.e. the count is approximate), and /// then later the exact number becomes available, then call /// [notifyListeners]. bool get isRowCountApproximate; /// Called to obtain the number of rows that are currently selected. /// /// If the selected row count changes, call [notifyListeners]. int get selectedRowCount; }