Image widget (asset, network) in Flutter

Introduction

Images make apps look nice and help users understand content better. The Image widget shows pictures from files or the internet.

Show a logo stored inside your app files.

Display a user's profile picture from a website.

Add background pictures to screens.

Show product photos loaded from online stores.

Syntax

Flutter

Image.asset('path/to/image.png')

Image.network('https://example.com/image.png')

Image.asset loads images bundled inside your app.

Image.network loads images from the internet using a URL.

Examples

Loads a local image named logo.png from the assets folder.

Flutter

Image.asset('assets/logo.png')

Loads the Flutter logo from the web.

Flutter

Image.network('https://flutter.dev/images/flutter-logo-sharing.png')

Loads a local photo and sets its size to 100x100 pixels.

Flutter

Image.asset('assets/photo.jpg', width: 100, height: 100)

Loads an online image and crops it to cover the space.

Flutter

Image.network('https://example.com/pic.jpg', fit: BoxFit.cover)

Sample App

This app shows two images stacked vertically: one local asset image and one from the internet. Both images are 150 pixels wide and centered on the screen.

Flutter

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('Image Widget Example')),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Image.asset('assets/flutter.png', width: 150),
              const SizedBox(height: 20),
              Image.network('https://flutter.dev/images/flutter-logo-sharing.png', width: 150),
            ],
          ),
        ),
      ),
    );
  }
}

Important Notes

Make sure to add local images to your pubspec.yaml under assets: to use Image.asset.

Network images need internet access and may take time to load; consider showing a placeholder or loading spinner.

You can control image size with width and height properties.

Summary

The Image widget displays pictures in Flutter apps.

Use Image.asset for local files bundled with your app.

Use Image.network to load images from the internet.

Practice

1. Which Flutter widget is used to display an image stored locally inside your app's assets folder?

easy

A. Image.asset

B. Image.network

C. Image.file

D. Image.memory

Solution

1. Step 1: Understand image sources in Flutter

   Flutter provides different constructors for Image widget depending on the source: asset, network, file, or memory.

2. Step 2: Identify the correct constructor for local assets

   Images bundled with the app are accessed using Image.asset.

3. Final Answer:

   Image.asset -> Option A

4. Quick Check:

   Local image = Image.asset [OK]

Hint: Local images use Image.asset constructor [OK]

Common Mistakes:

• Using Image.network for local files
• Confusing Image.file with assets
• Not adding assets to pubspec.yaml

2. Which of the following is the correct syntax to load an image from the internet in Flutter?

easy

A. Image.asset('https://example.com/image.png')

B. Image.network('https://example.com/image.png')

C. Image.file('https://example.com/image.png')

D. Image.memory('https://example.com/image.png')

Solution

1. Step 1: Identify the correct constructor for network images

   To load images from the internet, Flutter uses Image.network with the URL as a string parameter.

2. Step 2: Check syntax correctness

   The syntax Image.network('https://example.com/image.png') is correct and will load the image from the URL.

3. Final Answer:

   Image.network('https://example.com/image.png') -> Option B

4. Quick Check:

   Network image = Image.network [OK]

Hint: Use Image.network for URLs [OK]

Common Mistakes:

• Using Image.asset for URLs
• Passing URL to Image.file
• Missing quotes around URL string

3. What will be displayed when this Flutter code runs?

Image.asset('images/logo.png')

Assuming the image file exists and is declared in pubspec.yaml.

medium

A. An error because 'images/logo.png' is a network URL

B. A blank space because Image.asset cannot load images

C. The image 'logo.png' from the assets folder is shown

D. A loading spinner while the image downloads

Solution

1. Step 1: Confirm asset image usage

   The code uses Image.asset with a relative path 'images/logo.png', which means it loads a local asset image.

2. Step 2: Check conditions for display

   Since the image exists and is declared in pubspec.yaml, Flutter will display the image correctly.

3. Final Answer:

   The image 'logo.png' from the assets folder is shown -> Option C

4. Quick Check:

   Image.asset with valid asset = image shown [OK]

Hint: Image.asset shows local images if declared properly [OK]

Common Mistakes:

• Confusing asset path with network URL
• Not declaring asset in pubspec.yaml
• Expecting loading spinner for local images

4. Identify the error in this Flutter code snippet:

Image.asset('https://example.com/image.png')

medium

A. Using Image.asset with a network URL causes an error

B. Missing semicolon at the end

C. Image.asset requires a File object, not a string

D. The URL string is missing quotes

Solution

1. Step 1: Understand Image.asset usage

   Image.asset is for local asset files, not URLs.

2. Step 2: Identify misuse of URL with Image.asset

   Passing a network URL string to Image.asset causes a runtime error because it expects a local asset path.

3. Final Answer:

   Using Image.asset with a network URL causes an error -> Option A

4. Quick Check:

   Image.asset + URL = error [OK]

Hint: Image.asset only accepts local paths, not URLs [OK]

Common Mistakes:

• Thinking Image.asset works with URLs
• Ignoring asset declaration in pubspec.yaml
• Confusing Image.file with Image.asset

5. You want to display a local image named 'icon.png' stored in 'assets/icons/' folder and also show a fallback network image if the local image fails to load. Which Flutter code snippet correctly implements this?

hard

A. Image.file('assets/icons/icon.png', onError: () => Image.network('https://example.com/fallback.png'))

B. Image.network('assets/icons/icon.png', fallback: Image.asset('https://example.com/fallback.png'))

C. Image.asset('assets/icons/icon.png', fallbackImage: Image.network('https://example.com/fallback.png'))

D. Image.asset('assets/icons/icon.png', errorBuilder: (context, error, stackTrace) => Image.network('https://example.com/fallback.png'))

Solution

1. Step 1: Understand fallback handling in Image.asset

   Flutter's Image.asset supports an errorBuilder callback to handle loading errors and show alternative widgets.

2. Step 2: Check which option uses errorBuilder correctly

   Image.asset('assets/icons/icon.png', errorBuilder: (context, error, stackTrace) => Image.network('https://example.com/fallback.png')) uses errorBuilder to show a network image if the asset fails, which is the correct approach.

3. Final Answer:

   Image.asset with errorBuilder showing Image.network fallback -> Option D

4. Quick Check:

   Use errorBuilder for fallback images [OK]

Hint: Use errorBuilder in Image.asset for fallback images [OK]

Common Mistakes:

• Using fallback or onError props that don't exist
• Passing URLs to Image.asset directly
• Confusing Image.file with asset images