Flutter - ConstrainedBox Widget Last Updated : 26 Sep, 2022 Summarize Comments Improve Suggest changes Share Like Article Like Report ConstrainedBox is a built-in widget in flutter SDK. Its function is to add size constraints to its child widgets. It comes quite handy if we want a container or image to not exceed a certain height and width. It is also good to keep text in a wrapped layout by making the Text widget a child on ConstrainedBox. This functionality can also be found in SizedBox widget or else. Constructor of ConstrainedBox Class:ConstrainedBox( {Key key, @required BoxConstraints constraints, Widget child} )Property of ConstrainedBox Widget:constraints: This property takes in the BoxConstrain Class as the object. It puts constraints it's child widget using the functions of the BoxConstraints class. Example 1: Dart import 'package:flutter/material.dart'; //imported googles material design library void main() { runApp( /**Our App Widget Tree Starts Here**/ MaterialApp( home: Scaffold( appBar: AppBar( title: Text('GeeksforGeeks'), backgroundColor: Colors.greenAccent[400], centerTitle: true, ), //AppBar body: Center( /** ConstrainedBox Widget **/ child: ConstrainedBox( constraints: BoxConstraints.expand(height: 200, width: 200), child: Container( color: Colors.green, ), //Container widget ), //ConstrainedBox ), //Center ), //Scaffold ), //MaterialApp ); } Output: Explanation: In this flutter application we can see that the ConstrainedBox Widget is used to constrain the height and width of its child widget which is a Container. Here we have used BoxConstraints.expanded with the height and width parameter set to 200. We can notice that the height and width parameters are not mentioned in the Container widget it just expands to fill its parent widget. Example 2: Dart import 'package:flutter/material.dart'; //imported googles material design library void main() { runApp( /**Our App Widget Tree Starts Here**/ MaterialApp( home: Scaffold( appBar: AppBar( title: Text('GeeksforGeeks'), backgroundColor: Colors.greenAccent[400], centerTitle: true, ), //AppBar body: Center( /** ConstrainedBox Widget **/ child: ConstrainedBox( constraints: BoxConstraints.expand(height: 200, width: 200), child: Text( 'A Computer Science portal for geeks. It contains well written,well thought and well explained computer science and programmingarticles, quizzes, interview experiences and much more.', style: TextStyle(fontSize: 15), ), //Text ), //ConstrainedBox ), //Center ), //Scaffold ), //MaterialApp ); } Output: Explanation: In this flutter app the ConstrainedBox widget is used to wrap the text in a 200 X 200 box. Here also the text expands to fill the box as BoxConstraints.expand is used. This application of ConstrainedBox widget is very helpful when we want our text to not spill out of a certain bounded area. Comment More infoAdvertise with us A ankit_kumar_ Follow Improve Article Tags : Flutter Flutter-Widgets Similar Reads Flutter Tutorial This Flutter Tutorial is specifically designed for beginners and experienced professionals. It covers both the basics and advanced concepts of the Flutter framework.Flutter is Google’s mobile SDK that builds native Android and iOS apps from a single codebase. It was developed in December 2017. When 7 min read Top 50 Flutter Interview Questions and Answers for 2025 Flutter is an open-source, cross-platform application development framework. It was developed by Google in 2017. It is used to build applications for Android, iOS, Linux, Mac, Windows, and the web. Flutter uses the Dart programming language. It provides a simple, powerful, efficient, and easy-to-und 15+ min read What is Widgets in Flutter? 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