From Browser Preview to Android Device

VULK lets you generate Flutter apps from prompts and preview them in the browser. But the real value of a mobile app is running it on an actual phone. This tutorial walks through the entire APK export process -- from a finished Flutter project in the VULK editor to an installed app on your Android device.

Prerequisites

Before exporting, make sure your project meets these requirements:

• The project must be a Flutter project. APK export is only available for Flutter apps, not React, PHP, or Shopify projects. If you are unsure, check the file tree -- Flutter projects have a lib/ directory with .dart files and a pubspec.yaml.
• The app must compile in the preview. If the preview shows errors, the APK build will fail too. Fix any compilation issues first by asking VULK to resolve them in the chat.
• You need a paid plan. APK export is available on Builder, Pro, Team, and Business plans. Free plan users can generate and preview Flutter apps but cannot export APKs.

Step 1: Verify Your App in the Preview

Open your Flutter project in the VULK editor. The right panel shows the live preview of your app running in the browser via Flutter Web. Navigate through every screen and test the core interactions:

• Do all navigation routes work? Tap through your bottom navigation bar, drawer menu, or tab bar.
• Do forms validate correctly? Try submitting empty fields.
• Do lists render with the expected data?
• Are there any visual glitches -- overflow errors, misaligned elements, or missing images?

Fix issues before exporting. It is much faster to iterate in the browser preview than to rebuild an APK for each fix. Use follow-up prompts like:

The profile screen has a text overflow error on long usernames. Fix it by adding overflow ellipsis and a max width constraint.

The bottom navigation bar icons are not highlighting when I switch tabs. Make sure the selectedIndex updates correctly.

Step 2: Click Export APK

Once your app is stable in the preview, locate the Export APK button in the editor toolbar. It is in the top action bar, next to the Deploy button. Click it to start the build process.

What happens behind the scenes:

1. Dependency resolution. VULK runs the equivalent of flutter pub get to install all packages listed in your pubspec.yaml.
2. Dart compilation. Your Dart source code is compiled to native ARM machine code using Flutter's ahead-of-time (AOT) compiler. This is different from the web preview, which uses a JavaScript compilation target.
3. Resource bundling. Assets like fonts, images, and JSON files referenced in your pubspec.yaml are packaged into the APK.
4. APK assembly. The compiled code, resources, Android manifest, and Flutter engine are assembled into a single .apk file.
5. Debug signing. The APK is signed with a debug key so it can be installed on any Android device without Play Store distribution.

The build typically takes 30 to 90 seconds depending on project complexity and the number of dependencies.

Step 3: Download the APK

When the build completes, a download dialog appears with your .apk file. The file is named after your project -- for example, workout-tracker.apk. Click to download it to your computer.

The file size depends on your app's complexity. A typical VULK-generated Flutter APK ranges from 15 MB to 40 MB. This includes the Flutter engine (~10 MB), your compiled Dart code, and any bundled assets. Production-optimized APKs built locally with flutter build apk --release would be smaller, but the VULK export provides a fully functional build for testing and demonstration.

Step 4: Install on Your Android Device

There are two ways to get the APK onto your phone.

Option A: Direct transfer

1. Connect your Android device to your computer via USB.
2. Copy the .apk file to your device's Downloads folder.
3. On your phone, open a file manager app and navigate to Downloads.
4. Tap the .apk file.
5. Android will prompt you to allow installation from unknown sources (since this is not from the Play Store). Enable it for your file manager app.
6. Tap Install.

Option B: Self-transfer

1. Upload the .apk file to Google Drive, Dropbox, or send it to yourself via email or messaging app.
2. On your Android device, open the file from the cloud service or message.
3. Follow the same installation prompts as Option A.

After installation, your app appears in the app drawer like any other Android app. It has the Flutter default icon unless you specified a custom launcher icon in your prompt.

What the APK Includes

The exported APK is a standard Android application package. It contains:

• Your compiled Dart code running natively on ARM. No web view, no JavaScript bridge. This is a true native app with Flutter's rendering engine.
• Material Design components compiled into native widgets.
• Bundled assets -- any images, fonts, or data files referenced in your project.
• The Flutter engine -- the C++ runtime that powers Flutter's rendering pipeline.

The APK does not include:

• A release signing key. The app is signed with a debug certificate. To publish on the Google Play Store, you need to download the source code, configure a release keystore, and build a signed APK or App Bundle using flutter build appbundle --release.
• App Store metadata. No Play Store listing, screenshots, or descriptions are generated. Those are part of the publishing process, not the app itself.
• ProGuard or R8 optimization. The debug build does not apply code shrinking. A locally-built release version would be smaller.

Common Issues and Solutions

Build fails with dependency errors

Some Flutter packages require specific SDK versions or have platform-specific dependencies that conflict. If the build fails, check the error message in the export dialog. Common fixes:

The build failed because of a dependency conflict. Please update the http package to the latest version and make sure all dependencies are compatible.

App crashes on launch

This usually means a runtime error in your Dart code that did not surface in the web preview. Common causes include platform channel calls (trying to access a native API that works differently on Android vs web) or null reference errors in data handling. Check the preview carefully and fix any issues before re-exporting.

App looks different on phone vs preview

The web preview uses Flutter Web rendering, while the APK uses the Skia-based native renderer. Minor differences in text rendering, shadow quality, and antialiasing are expected. If the layout is significantly different, it is likely a responsive issue -- the preview iframe may be a different width than your phone screen. Add responsive checks:

Make the home screen layout adapt to different screen widths. On screens narrower than 360dp, use a single-column layout instead of the two-column grid.

APK is too large

Flutter APKs include the engine, which adds approximately 10 MB. If your app includes large assets (high-resolution images, bundled JSON datasets), the size increases. To reduce size, use network-loaded images instead of bundled assets, and consider downloading the source code to build a release APK with --split-per-abi to produce architecture-specific builds (~8 MB for arm64).

After the APK: Next Steps

The exported APK is ideal for testing, demos, and sharing with stakeholders. For production distribution, you will want to:

1. Download the source code from VULK (ZIP export).
2. Set up a local Flutter environment with Android Studio or VS Code.
3. Configure app signing with a release keystore.
4. Customize the app icon using the flutter_launcher_icons package.
5. Build a release App Bundle with flutter build appbundle --release.
6. Submit to Google Play Console for distribution.

VULK gets you from idea to working Android app in minutes. The APK export lets you hold that app in your hand and show it to real users. The path from there to the Play Store is a standard Flutter publishing workflow -- your code is clean, standard Dart, and ready for production tooling.

Try it at vulk.dev.