Flutter for Beginners by Alessandro Biessek

Author:Alessandro Biessek [Alessandro Biessek]
Language: eng
Format: epub
Tags: COM051460 - COMPUTERS / Programming / Mobile Devices, COM051280 - COMPUTERS / Programming Languages / Java, COM051390 - COMPUTERS / Programming / Open Source
Publisher: Packt Publishing
Published: 2019-09-12T12:54:08+00:00

Let's check out how to respond to a size change on the screen. In this example, we will change the way two widgets are displayed based on the available space. So, the widgets are displayed one on top of the other when there is not sufficient room for them (we evaluate this using the BoxContraints instance given by the LayoutBuilder widget), or side-by-side when there is more space available (such as in the landscape position):

class MyApp extends StatelessWidget {

@override

Widget build(BuildContext context) {

return MaterialApp(

home: LayoutBuilder(

builder: (BuildContext context, BoxConstraints constraints) {

// build the layout based on constraints values

}

)

)

}

}

As you can see, we have added a LayoutBuilder widget, and we can build the layout based on the given constraints:

if (constraints.maxWidth <= 500) {

return Column(

mainAxisSize: MainAxisSize.max,

children: <Widget>[

Expanded(

child: Container(

color: Colors.green,

child: Center(child: Text("1")),

),

),

Expanded(

child: Container(

color: Colors.blue,

child: Center(child: Text("2")),

),

),

],

);

}

Conditionally, we display a Column widget when the available width is less than 500. And when we have enough room we change the returned widget:

return Row(

mainAxisSize: MainAxisSize.max,

children: <Widget>[

Expanded(

child: Container(

color: Colors.yellow,

child: Center(child: Text("1")),

),

),

Expanded(

child: Container(

color: Colors.purple,

child: Center(child: Text("2")),

),

),

],

);

In this case we return a Row widget, as we have sufficient space (greater than 500).

This is how it looks in different orientations:

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