Debugging is one of the most essential skills for every Flutter developer. Whether you’re fixing UI glitches, tracking logic errors, or diagnosing performance bottlenecks, Flutter provides a rich set of debugging tools that work seamlessly across IDEs like Android Studio and VS Code, as well as on emulators and real devices.
This article will guide you through using the Flutter debugger, covering breakpoints, console logs, debugging tools, performance profiling, and best practices.
Flutter Debug Mode
When you run your Flutter app in debug mode, it enables:
- Hot reload for faster code iteration
- Assertions for catching errors early
- Breakpoints and step-by-step debugging
- Debugging tools like the Flutter Inspector
To start in debug mode:
flutter run --debugDebugging Flutter apps:
There is a wide range of tools and features to help debug Flutter applications. The following tools and features are available:
- DevTool is a suite of performance and profiling tools that are run in a browser.
- Android Studio / IntelliJ and VS Code support an inbuilt source-level debugger with the ability to set breakpoints, step through the code, and examine the values.
- Logging view, a widget inspector working in DevTools, and also indirectly from Android Studio & IntelliJ. The inspector allows you to examine a visual representation of the widget trees, inspect individual widgets and their property values, enable the performance overlay, and more.
Console output: Console output for the running app (stdout and stderr) is displayed in the console, below the source code area. You can also see the output in the screenshot.
Improve workflow with a full view of releases, so you can mark errors as resolved and prioritize live issues. In Flutter debugging entire code runs line by line for a single instance. Also learn in which version a particular bug first appeared, merge duplicates, and know if things regress in a future release. Add commit data to automatically suggest an owner of each application error.
Using the Debugger:
It works with all Flutter & Dart applications.
Example:
First, we import the Flutter package and particular class (material) using the “import ‘package Flutter /material dart. Basically, Dart is developed by Google for multiple platforms to build mobile, desktop, server, and web applications. Flutter is very rich in classes, so we import a particular class. Here we import the material class. “Import dart: developer as dev.” Here we import the developer tools such as the debugger and inspector. In this example basically, we are using the counter class.
In this image, we use the dev.debugger() function.
After this call the actually debugging is by the developer can see every iteration of the code the check every iteration of code run, and also see every action in the console output. That makes the developer responsible for the actual flow of the code, and actually, the action is done in which iteration.
Easy to figure out the useless code line or code in the code part, which is not useful work, or is not useful for the developer, that I,s the application of debugging the code or application.
DevTools
1. Full source-level debugger: A full source-level debugger is a type of debugger that shows the expression in the source code that resulted in a particular machine code loaded in the memory of the system. It is a very good tool for debugging execution programs. It is useful when working with crashed programs that leave dump files. In source-level debugger statements in the source and location of that code in the executable.
2. Supporting breakpoints: Supporting breakpoints is a great feature. The feature provided by the debugger. When performing a hot restart for a Flutter application, user breakpoints are cleared. For setting up breakpoints in any program, click the left margin in the source area. Click once to set breakpoints. Which also shows in the breakpoints area on the left.
3. Stepping: Stepping means using Step into to step into a method invocation, stopping at the first executable line in the invoked method. Use Step over to step over a method invocation: This steps through source lines in the current method in your program. Use Step out to step out of the current method, without stopping at any intermediary lines in the program.
4. Variable inspection: Variable inspection in the Flutter widget inspector is a powerful tool for visualizing and exploring Flutter widget trees. The Flutter SDK uses widgets as the core building block of application form controls such as text, buttons, and toggles, to layouts such as centering, padding, rows, and columns. The variable inspector tool is employed to visualize and explore Flutter widget trees and can be used for the following: understanding existing layouts that are already in it, and diagnosing layout issues.
When we use the debugger tab, we should see the source for the main entry points of our application loaded in the debugger.