How to add image in Flutter

I think the error is caused by the redundant ,

flutter:
  uses-material-design: true, # <<< redundant , at the end of the line
  assets:
    - images/lake.jpg

I'd also suggest to create an assets folder in the directory that contains the pubspec.yaml file and move images there and use

flutter:
  uses-material-design: true
  assets:
    - assets/images/lake.jpg

The assets directory will get some additional IDE support that you won't have if you put assets somewhere else.

How to include images in your app

1. Create an assets/images folder

• This should be located in the root of your project, in the same folder as your pubspec.yaml file.
• In Android Studio you can right click in the Project view
• You don't have to call it assets or images. You don't even need to make images a subfolder. Whatever name you use, though, is what you will register in the pubspec.yaml file.

2. Add your image to the new folder

• You can just copy your image into assets/images. The relative path of lake.jpg, for example, would be assets/images/lake.jpg.

3. Register the assets folder in pubspec.yaml

• Open the pubspec.yaml file that is in the root of your project.

• Add an assets subsection to the flutter section like this:

    flutter:
      assets:
        - assets/images/lake.jpg
  

• If you have multiple images that you want to include then you can leave off the file name and just use the directory name (include the final /):

    flutter:
      assets:
        - assets/images/
  

4. Use the image in code

• Get the asset in an Image widget with Image.asset('assets/images/lake.jpg').

• The entire main.dart file is here:

    import 'package:flutter/material.dart';
  
    void main() => runApp(MyApp());
  
    class MyApp extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          home: Scaffold(
            appBar: AppBar(
              title: Text("Image from assets"),
            ),
            body: Image.asset('assets/images/lake.jpg'), //   <--- image
          ),
        );
      }
    }
  

5. Restart your app

When making changes to pubspec.yaml I find that I often need to completely stop my app and restart it again, especially when adding assets. Otherwise I get a crash.

Running the app now you should have something like this:

Further reading

• See the documentation for how to do things like provide alternate images for different densities.

Videos

The first video here goes into a lot of detail about how to include images in your app. The second video covers more about how to adjust how they look.

• Flutter Tutorial - 1/2 Image - Deep Dive
• Flutter Tutorial - 2/2 Image - Deep Dive