// Copyright 2015 The Chromium 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/widgets.dart'; import 'material.dart'; /// Asserts that the given context has a [Material] ancestor. /// /// Used by many material design widgets to make sure that they are /// only used in contexts where they can print ink onto some material. /// /// To call this function, use the following pattern, typically in the /// relevant Widget's build method: /// /// ```dart /// assert(debugCheckHasMaterial(context)); /// ``` /// /// Does nothing if asserts are disabled. Always returns true. bool debugCheckHasMaterial(BuildContext context) { assert(() { if (context.widget is! Material && context.ancestorWidgetOfExactType(Material) == null) { final Element element = context; throw new FlutterError( 'No Material widget found.\n' '${context.widget.runtimeType} widgets require a Material widget ancestor.\n' 'In material design, most widgets are conceptually "printed" on a sheet of material. In Flutter\'s material library, ' 'that material is represented by the Material widget. It is the Material widget that renders ink splashes, for instance. ' 'Because of this, many material library widgets require that there be a Material widget in the tree above them.\n' 'To introduce a Material widget, you can either directly include one, or use a widget that contains Material itself, ' 'such as a Card, Dialog, Drawer, or Scaffold.\n' 'The specific widget that could not find a Material ancestor was:\n' ' ${context.widget}\n' 'The ownership chain for the affected widget is:\n' ' ${element.debugGetCreatorChain(10)}' ); } return true; }); return true; }