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// 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 'basic.dart';
import 'framework.dart';
/// A widget whose child can be mutated.
class Placeholder extends StatefulWidget {
Placeholder({ Key key }) : super(key: key);
@override
PlaceholderState createState() => new PlaceholderState();
}
/// State for a [Placeholder] widget.
///
/// Useful for setting the child currently displayed by this placeholder widget.
class PlaceholderState extends State<Placeholder> {
/// The child that this widget builds.
///
/// Mutating this field will cause this widget to rebuild with the new child.
Widget get child => _child;
Widget _child;
void set child(Widget child) {
if (_child == child)
return;
setState(() {
_child = child;
});
}
@override
Widget build(BuildContext context) {
if (_child != null)
return child;
return new SizedBox(width: 0.0, height: 0.0);
}
}