How To Convert APK To Flutter Code – A Practical Guide?

Published on September 25th, 2024

APK apps are beneficial as they allow users to install apps directly on their Android devices, giving access to apps beyond Google Play Store. But what if you want to extend its capabilities beyond Android?

Well, one way is to convert APK to Flutter code!

By converting your existing APK into Flutter code, you can achieve several benefits that native app development does not offer. These include cross-platform compatibility, high performance, and faster development and maintenance.

However, the process is not as simple as you might think. You can extract assets like images, layouts, etc., from the APK package. But, you will need to reverse-engineer some components to implement them in Flutter’s Dart language.

Although challenging, the long-term benefits of this conversion make the efforts worth it.

In this practical guide, we will cover the step-by-step process to smoothly transition your APK to Flutter. We will explore in detail how to extract useful components from APK, identify key functionalities, and re-write them in Flutter.

Let’s begin with understanding the challenges of converting an APK to Flutter.

Challenges In Migrating APK To Flutter Code

Converting an APK to Flutter can be a complex process. Below are two common challenges most developers face when converting APK to Flutter:

• Code Analysis

Understanding APK’s code and structure along with identifying the components to be converted to Flutter is often time-consuming. It involves analyzing the APKs architecture thoroughly and finding the equivalent Flutter architecture and widgets. Since the APK codebase is quite complex, it makes it difficult to identify the key components to covert.

• Reverse Engineering

It is often difficult to decompile the APK file to access the original code. This is especially true if the APK code is unfathomable for the humans. For the decompiling process, it is important to have in-depth understanding of the APKs internal structure.

You must also be able to navigate through complex code. Further, decompilation tools not necessarily generate accurate results every time. This can further escalate the issue of understanding the code.

While the process of converting APK to Flutter code is challenging, it can still be overcomes with the right approach.

Also Read: How to Convert Your Existing Mobile App to Flutter Easily?

Steps To Convert APK To Flutter Code 

Here are the steps involved in the process of converting APK to Flutter code:

1. Extract Components From The APK (Reverse Engineering)

The first step in the conversion process is to extract useful components from the APK file. You cannot access the source code directly, as the APK files are compiled. But you can use certain tools to decompile the APK and extract required components.

Decompile The APKs 

Use tools like APKTool or JADX to decompile the APK. APKTool converts the APK into a more readable format and retrieve assets such as images, and layout XML files. Further, the JADX tool coverts DEX (Dalvik Executable) files into Java source code. This give information about the app’s logic.

Here’s the process:

• Install APKTool or JADX.
• Run the tool to decompile the APK. For APKTool, run apktool d your_app.apk to access a directory and manifest files.
• For JADX, use the command jadx -d output_folder your_app.apk to access Java source files.

Extract Resources 

Find resources such as strings, layout XML files, images, and other assets in the decompiled APK. Save these assets to be used in the Flutter project for recreating the UI/UX design (look and feel) of the app.

Analyze Code Logic 

• DEX Files: Review the decompiled Java code to understand the app’s functionalities, logic, and structure. This will help you in imitating the app functionality in Flutter.

2. Reimplement Core Functionalities In Flutter

The actual conversion process begins with reimplementing the app functionality into Flutter. This can be done only once you have completed the extraction of necessary components.

As you know, Flutter uses Dart! Hence, the code structure and syntax are different from that of Kotlin or Java.

Here are the steps:

Setup A Flutter Project

• Create a new Flutter project using the command flutter create project_name.
• Understand the Flutter’s project structure, including lib for Dart code, pubspec.yaml for dependencies, and assets for images and resources.

Write The Dart Code

• Re-implement the app’s core functionality using Dart. Start with the backend logic, ensuring that features such as data handling, login, and requests work correctly.
• Use Dart packages to replace Android-specific libraries. For example, http for network requests instead of Android’s networking APIs.

Implement State Management

Choose a state management solution such as Riverpod, Provider, or Bloc. Run state management to manage data flow and UI updates efficiently.

 3. Rebuild The User Interface

One of the major benefits of Flutter is that it can create eye-catching, cross-platform UIs from a single codebase. To rebuild the app’s UI, you will need to translate the Android XML layouts to the widget-based system of Flutter.

Translate Layouts

• Convert Android XML layouts into Flutter’s widget-based UI, including Container, Column, Row, and Stack to rebuild the app’s interface.
• Redesign UI elements like buttons, images, and text fields using Flutter’s widgets and styles.

Apply Design Principles 

• Use Flutter’s material design for Android-Like aesthetics.
• Rebuild any animations using Flutter’s animation framework, using AnimatedContainer, FadeTransition, 

4. Handle Android-Specific Libraries 

One of the major challenges of converting APK to Flutter code is to deal with Android-specific features or libraries. To overcome these challenges, you will need to find alternative ways to integrate Android features into Flutter.

Integrate Platform Channels 

• Use Flutter’s platform channels to call native Android code for Android-specific features, like backgrounds tasks, or sensors.
• For this, write platform-specific code in Kotlin/Java and communicate with it from Dart using method channels.

Find Equivalent Packages

• Search for Flutter plugins that offer similar functionality to the Android libraries used in your app. For instance, use firebase_auth for authentication and google_maps_flutter. 

5. Ensure Smooth Background Integration

To convert your existing app into Flutter, you will need to reconfigure its backend services for Flutter. These may include API, databases, or third-party integrations. This is an important step that ensures seamless app functionality. Here are the steps:

Connect APIs

• Use Dart’s http package or other networking libraries to integrate with backed services. Make sure that API endpoints are connected correctly and handle responses and errors.

Set Up Local Databases

• Use sqfLite for SQLite databases or hive for NoSQL databases.
• Move any local data from the Android app to Flutter’s database solutions.

Integrate Third-Party Services 

Integrate third-party services, like Firebase that your app use, into Flutter using relevant packages.

6. Testing & Debugging 

Once you have followed the above steps to re-implement your app in Flutter, test the app thoroughly. Test your re-implemented app for user experience, functionality, and platform compatibility.

Perform Cross-Platform Testing 

Test the app on multiple Android and iOS devices to ensure compatibility and performance. You can use emulators or real devices for testing.

Debug Issues

Use Flutter’s Dev tools to debug and monitor performance. Detect and address issues in UI, functionality, and performance.

Optimize User Experience 

Collect user feedback and make necessary changes. Make sure the app is responsive, easy-to-use, and performs smoothly across different devices.

The Final Words

To convert APK to Flutter code, you should practice the right approach and follow each step carefully. This not only helps you overcome the challenges of converting APK to Flutter code but also reap the benefits of cross-platform development. By following these steps and use Flutter’s extensive tools and libraries, you can effectively migrate your app and boost its functionality and performance.