Flutter Hot reloading not working in android studio(mac)

Question

While working on mac machine I found that hot reloading not working in Android Studio. I don't know what's wrong :)

Here is the code which not reloading(I am changing the Hello world text to Flutter Sample text)

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
    home: new Scaffold(
      appBar: new AppBar(
        title: new Text("Demo Project"),
      ),
      body: Center(child: new Text("Hello World!!!")),
    ),
  ));
}

Please see this below video with the link https://www.dropbox.com/s/e7viujcgv8w0mtr/hot_reload.mp4?dl=0

This not stop my development, But I am concerned why it is happening.

Solution 1

Flutter Documentation says "Hot reload loads code changes into the VM and re-builds the widget tree, preserving the app state; it doesn’t rerun main() or initState()"

So, it looks like if the app logic resides outside the main method, then Hot Reloading works. Try to refactor your app like below and then do Restart (green button). Any subsequent changes you make, will be HOT RELOADED when saved.

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text("Demo Project"),
        ),
        body: Center(child: new Text("Hello World!!!")),
      ),
    );
  }
}

UPDATE: Hot Reload will not work if you are adding new assets (like images, or medial files). In those cases you will have to restart the App.

Solution 2

Try This

The solution on GitHub Reloaded 0 of NNN libraries in Xms

Android Studio uses IDEA to import files automatically, Like this

import 'file///F:/flutter_project/lib/home_page.dart';

Change it to

import 'package:flutter_project/home_page.dart';

Solution 3

in the terminal, run

flutter doctor -v

flutter upgrade

Also, try File > Invalidate Caches / Restart... from Android studio menu

Solution 4

Wrap your code with a StatefulWidget like shown in the code below. This might be confusing when watching old tutorials because it used to work without it on an earlier Flutter Version.

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(home: MyApp()));
}

class MyApp extends StatefulWidget {
  MyApp({Key key}) : super(key: key);

  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Demo Project"),
      ),
      body: Center(child: new Text("Hello World!!!")),
    );
  }
}

Solution 5

If I'm not mistaken, hot reload calls the build method of your widget, as the change you made weren't made inside a build method, it didn't change anything in the screen.

Try changing the texting inside the MyWidget Build method and see if it works.

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
    home: new Scaffold(
      appBar: new AppBar(
        title: new Text("Demo Project"),
      ),
      body: new MyWidget(),
    ),
  ));
}

class MyWidget extends StatelessWidget {
  const MyWidget({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Center(child: new Text("Hello World!!!"));
  }
}

View more solutions

Comments

[shb]

This is weird, it happened to me couple of times too. I closed everything, restarted the project and then it worked fine.

[ישו אוהב אותך]

My question here a little out of the topic, did the some problem is happened when you're using IntelliJ?

[Jitesh Mohite]

I am not using IntelliJ, sorry.

[neobie]

My hot reload is working in Visual studio code, but not working in Android Studio, any one ?

[Piyin]

I think the correct answer is Invin's; stackoverflow.com/a/61567821/5503625 You should mark it as accepted

[Luiz França]

I had this problem once and closing android studio and reopening did the trick. @jitsm555.

[George]

The video on the question shows the hot reload happening, the flutter message, but nothing happening on the emulator, so it's not a shortcut issue.

[Simple UX Apps]

File > Invalidate Caches / Restart solved it for me. Thanks.

[snake_eyes]

how to update it? although I applied the command flutter upgrade and got everything is update 2 date.

[Abdoulaye BARRY]

Delete your flutter sdk. Download and extract the new from flutter.io website.

[Vu Pham]

This solves my problem. I am working with Flutter version 1.18.0-11.1.pre.

[Invin]

Glad, I could help

[Konstantin Kozirev]

The use of MaterialApp is not justified in this case. It can be just runApp(new myApp()) in void main(). If you use MaterialApp, then it will be in different uglish styling.

[Konstantin Kozirev]

Moreover, I just checked and it also works with StatelessWidget. So absolutely no reason to use StatefulWidget and MaterialApp. Hotreload works with StatelessWidget.

[DYS]

Big thanks! I doubt it's something to do with latest Flutter upgrade, only to find out your answer explains the culprit.

[Bala]

This is the correct solution, if hot reload doesn't work even when hot reload preferences are enabled.

[Petro]

Can you explain more with some example code?

[Kaigo]

Do you mean 'or' instead of 'of'?

[Suj]

yes Invalidating caches fixes for me as well