Flutter - Set Widget Opacity

In this tutorial, we are going to show you how to set opacity of any widget in Flutter, including how to set the initial opacity and update the opacity value.

Sometimes, we want to make a widget looks more transparent by setting opacity. In Flutter, it can be done easily by using Opacity widget. Here are the options you can use in the constructor.

OptionDescription
Key keyThe Opacity widget's key.
double opacity (required)Alpha value of the child.
boolean alwaysIncludeSemanticsWhether the semantic information of the children is always included.
Widget childThe widget whose opacity will be controlled.

The opacity value must be between 0.0 and 1.0 (inclusive). At value 0.0, the child looks invisible (transparency is 100%). At 1.0, the transparency is 0%.

Code Example

Below is an example how to use the Opacity widget. In this example, there is a button whose opacity is set to 0.5 at the beginning. Tap it to adjust the opacity value. To make it possible to update the value, it's stored as a state.

  import 'package:flutter/material.dart';
  
  class OpacityExample extends StatefulWidget {
    @override
    _OpacityExampleState createState() {
      return _OpacityExampleState();
    }
  }
  
  class _OpacityExampleState extends State<OpacityExample> {
    double _opacity = 0.5;
  
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Opacity Tutorial',
        home: Scaffold(
          appBar: AppBar(
            title: Text('Opacity Tutorial'),
          ),
          body: Padding(
            padding: EdgeInsets.all(15.0),
            child: Center(
              child: Opacity(opacity: _opacity,
                child: RaisedButton(
                    child: Text('Woolha.com'),
                    onPressed: () {
                      setState(() {
                        double newOpacity = _opacity + 0.5;
                        _opacity = newOpacity > 1 ? 0 : newOpacity;
                      });
                    },
                ),
              ),
            ),
          )
        ),
      );
    }
  }
  
  void main() => runApp(OpacityExample());