debugging.md

title	Debugging your add-to-app module
short-title	Debugging
description	How to run, debug, and hot reload your add-to-app Flutter module.

Debugging your add-to-app module

Once you've integrated the Flutter module to your project and used Flutter's platform APIs to run the Flutter engine and/or UI, you can then build and run your Android or iOS app the same way you run normal Android or iOS apps.

However, Flutter is now powering the UI in places where you're showing a FlutterActivity or FlutterViewController.

Debugging

You may be used to having your suite of favorite Flutter debugging tools available to you automatically when running flutter run or an equivalent command from an IDE. But you can also use all your Flutter debugging functionalities such as hot reload, performance overlays, DevTools, and setting breakpoints in add-to-app scenarios.

These functionalities are provided by the flutter attach mechanism. flutter attach can be initiated through different pathways, such as through the SDK's CLI tools, through VS Code or IntelliJ/Android Studio.

flutter attach can connect as soon as you run your FlutterEngine, and remains attached until your FlutterEngine is disposed. But you can invoke flutter attach before starting your engine. flutter attach waits for the next available Dart VM that is hosted by your engine.

Terminal

Run flutter attach or flutter attach -d deviceId to attach from the terminal.

{% include docs/app-figure.md image="development/add-to-app/debugging/cli-attach.png" caption="flutter attach via terminal" %}

VS Code

Select the correct device using the status bar in VS Code, then run the Flutter: Attach to Flutter on Device command from the command palette.

{% include docs/app-figure.md image="development/add-to-app/debugging/vscode-attach.png" caption="flutter attach via VS Code" %}

Alternatively, create a .vscode/launch.json file in your Flutter module project to enable attaching using the Run > Start Debugging command or F5:

{
  name: "Flutter: Attach",
  request: "attach",
  type: "dart",
}

IntelliJ / Android Studio

Select the device on which the Flutter module runs so flutter attach filters for the right start signals.

{% include docs/app-figure.md image="development/add-to-app/debugging/intellij-attach.png" caption="flutter attach via IntelliJ" %}

Wireless Debugging

You can debug your app wirelessly on an iOS device using flutter attach:

1. Ensure that your device is wirelessly connected to Xcode as described in the MacOS installation guide.
2. Open Xcode > Product > Scheme > Edit Scheme
3. Select the Arguments tab
4. Add either --observatory-host=0.0.0.0 for IPv4, or --observatory-host=::0 for IPv6 as launch argument

{:.mw-100}