How to make a Flutter button log to the console when pressed?-CodePudding

I'm coming from JavaScript where every other line is console.log('Logged!'). How is this done in Flutter? The Flutter docs show there is a log() feature. I tried to make a button log to the console when clicked but it didn't work.

I'll show the code snippet first, then the error message, then the full code.

import 'dart:developer';

ElevatedButton(
          style: style,
          onPressed: () => {
            log('Clicked!');
          },
          child: const Text('My Button'),
        ),

The error message:

lib/main.dart:45:27: Error: Expected '}' before this.
            log('Logged!');
                          ^

And my full code:

import 'package:flutter/material.dart';
import 'dart:developer';

void main() => runApp(const HelloWorld());

class HelloWorld extends StatelessWidget {
  const HelloWorld({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    const String appTitle = 'MyApp';
    return MaterialApp(
      title: appTitle,
      home: Scaffold(
        appBar: AppBar(title: const Text(appTitle)),
        body: const FullNameField(),
      ),
    );
  }
}

class FullNameField extends StatelessWidget {
  const FullNameField({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    final ButtonStyle style = ElevatedButton.styleFrom(textStyle: const TextStyle(fontSize: 20));

    return Column(
      crossAxisAlignment: CrossAxisAlignment.center,
      children: <Widget>[
        Container(
          // alignment: Alignment.center,
          padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 16),
          child: TextFormField(
            decoration: const InputDecoration(
              border: UnderlineInputBorder(),
              labelText: 'Enter your username',
            ),
          ),
        ),
        ElevatedButton(
          style: style,
          onPressed: () => {
            log('Clicked!');
          },
          child: const Text('My Button'),
        ),
      ],
    );
  }
}

Thanks!

CodePudding user response：

You can use debugPrint

Prints a message to the console, which you can access using the "flutter" tool's "logs" command ("flutter logs").

onPressed: () => {
  debugPrint("Logged!"),
},

Also, you can use print() method, which I is not recommended.

CodePudding user response：

The problem was a semi-colon at the end of log('Clicked!');. When I changed the semi-colon to a comma it worked. I'm coming from JavaScript. :-)

 ElevatedButton(
          style: style,
          onPressed: () => {
            log('Clicked!'),
          },
          child: const Text('Get Fortune'),
        ),

And debugPrint('Clicked!'), and print('Clicked!'), also work.

I just figured out that the arrow function has to be followed by commas but without the arrow function you use semi-colons.

onPressed: () {
    
            log('Clicked!');
          },

vs.

onPressed: () => {
    
            log('Clicked!'),
          },