Handling Taps

We not only want to display information to our users, we want our users tointeract with our apps! So how do we respond to fundamental actions such astapping and dragging? We’ll use theGestureDetectorWidget!

Say we want to make a custom button that shows a snackbar when tapped. How wouldwe approach this?

Directions

• Create the button
• Wrap it in a GestureDetector with an onTap callback

// Our GestureDetector wraps our button
GestureDetector(
  // When the child is tapped, show a snackbar
  onTap: () {
    final snackBar = SnackBar(content: Text("Tap"));

    Scaffold.of(context).showSnackBar(snackBar);
  },
  // Our Custom Button!
  child: Container(
    padding: EdgeInsets.all(12.0),
    decoration: BoxDecoration(
      color: Theme.of(context).buttonColor,
      borderRadius: BorderRadius.circular(8.0),
    ),
    child: Text('My Button'),
  ),
);

Notes

• If you’d like to add the Material Ripple effect to your button, please see the “Adding Material Touch ripples” recipe.
• While we’ve created a custom button to demonstrate these concepts, Flutter includes a handful of buttons out of the box: RaisedButton, FlatButton, and CupertinoButton

Complete example

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final title = 'Gesture Demo';

    return MaterialApp(
      title: title,
      home: MyHomePage(title: title),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(child: MyButton()),
    );
  }
}

class MyButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // Our GestureDetector wraps our button
    return GestureDetector(
      // When the child is tapped, show a snackbar
      onTap: () {
        final snackBar = SnackBar(content: Text("Tap"));

        Scaffold.of(context).showSnackBar(snackBar);
      },
      // Our Custom Button!
      child: Container(
        padding: EdgeInsets.all(12.0),
        decoration: BoxDecoration(
          color: Theme.of(context).buttonColor,
          borderRadius: BorderRadius.circular(8.0),
        ),
        child: Text('My Button'),
      ),
    );
  }
}