Rewriting the code of an existing game on the platform Android is a complex but often necessary process for developers seeking to extend the life cycle of their project. Over time, even the highest-quality source code becomes overgrown with technical debt, outdated libraries and ineffective algorithms, which leads to a drop FPS and increase in memory consumption. Refactoring allows you not only to correct errors, but also to adapt the project to modern standards of mobile device performance.
In this article we will look at the key stages of transforming legacy code into an optimized structure. You will learn what tools to use for analysis, how to safely replace architectural components, and what to pay attention to when working with the graphics pipeline. Deep modernization Requires a systematic approach so as not to break the working game logic.
Often the need to rewrite code arises due to changing versions Android SDK or discontinuation of support for old APIs. Ignoring these requirements leads to the application crashing on new devices or not passing moderation in Google Play. The rewriting process is not just copy-paste, it is a rethinking of the architecture taking into account modern hardware capabilities.
Audit of the current state of the project and identifying bottlenecks
Before making changes to the source code, it is necessary to conduct a thorough audit of the existing database. Using profilers such as Android Studio Profiler or Unity Profilerallows you to visualize the load on the processor and memory in real time. You should clearly understand which game modules consume the most resources and where the main rendering delays occur.
Pay attention to usage Garbage Collector. Frequent garbage collections are one of the main causes of micro-freezes in games. Analyze the logs and find places where excessive object creation occurs, especially within the game loop Update. Optimizing memory allocations often gives a more noticeable performance boost than rewriting graphics.
⚠️ Attention: Before starting a large-scale refactoring, be sure to create a full backup of the project in version control
Git. Rolling back changes may be necessary at any time if the new architecture leads to critical errors.
It is also worth checking that third-party dependencies are up to date. Many older libraries may conflict with newer versions or contain security vulnerabilities. Make a list of all the plugins you use and evaluate the need to replace them with more modern analogues or native solutions. Gradle or contain security vulnerabilities. Make a list of all the plugins you use and evaluate the need to replace them with more modern analogues or native solutions.
Selecting a migration strategy and architectural patterns
After analysis, you need to choose a rewriting strategy. There are two main approaches: complete (rewrite) from scratch or gradual refactoring of modules. A complete restart is justified only if the current architecture has completely outlived its usefulness and cannot be fixed locally. In most cases, it is more effective to use the strategy gradual replacement.
When working with code on Java or Kotlin it is recommended to implement modern architectural patterns, such as MVVM or ECS (Entity-Component-System) for game logic. This will allow you to share responsibility between components and simplify testing of individual parts of the game. Clear separation of rendering logic, physics, and interface is critical for stability.
If you are using a cross-platform engine, make sure your code does not rely heavily on platform-specific features unless necessary. Abstracting system calls across interfaces will make future ports and updates easier. Using Dependency Injection will help manage complex dependency graphs in large projects.
Use static code analysis tools such as Lint or SonarQube to automatically search for "code smells" and potential bugs before starting manual refactoring.
Optimize rendering and work with graphics
The graphics subsystem is the most resource-intensive component of any game. When rewriting code, pay special attention to optimizing draw calls (Draw Calls). Batching and using texture atlases can significantly reduce the load on the GPU. GPU.
Check the use of shaders. Complex calculations in pixel shaders can become a bottleneck on mobile devices with limited memory bandwidth. Simplify math operations where possible without apparent loss of quality, and use levels of detail (LOD) for remote objects.
| Optimization method | Impact on CPU | Impact on GPU | Implementation complexity |
|---|---|---|---|
| Static Batching | Low | High (decrease) | Low |
| Object Pooling | Medium (decrease in GC) | Neutral | Average |
| Level of Detail (LOD) | High (decrease) | High (reduction) | High |
| Texture Compression (ASTC) | Neutral | Medium (memory reduction) | Low |
Don't forget about texture memory management. Loading textures at the wrong time can cause a spike in memory consumption and crash the application. Implement asynchronous resource loading and pre-calculate the required amount of video memory for each level of the game.
The secret to optimizing shaders
Use fixed point instead of floating point in shaders for mobile devices, where possible. Low-precision operations often run faster on mobile GPUs and save energy.
Refactoring game logic and physics
Game logic often becomes confusing due to accumulated conditional statements and global variables. When rewriting, aim to create modular classes with clear responsibilities. Avoid using Singleton for everything, as this complicates testing and creates hidden dependencies.
The physics engine requires special attention. Make sure that physics calculations are placed in a separate thread or optimized loop that does not block the main rendering thread. Using simplified colliders (for example, spheres or capsules instead of complex meshes) can significantly speed up collision calculations without compromising gameplay.
⚠️ Note: Graphics engine APIs and physics libraries may change in new versions. Always check method syntax and initialization parameters with the official documentation before implementing it into production.
Introducing an event system (Event System) instead of direct method calls between objects will make the code more flexible. This will make it easy to add new mechanics without rewriting existing classes. Decoupling (decoupling) of components is the key to project scalability.
☑️ Logic refactoring checklist
Working with memory and resource management
Memory management in Android has its own characteristics due to the limited amount of RAM and the aggressive operation of the garbage collection system. When rewriting code, it is critical to minimize the creation of temporary objects. Use object pools (Object Pooling) for frequently created and destroyed entities, such as bullets or particles.
Watch out for memory leaks, especially those related to context Activity or Context. Long-lived context references may prevent memory from being freed even after the activity is closed. Use weaker references (WeakReference) where appropriate, and carefully check the lifecycle of objects.
For working with large amounts of data, consider using pre-allocated data structures. Dynamic expansion of arrays (as in ArrayList) causes memory copying, which is expensive in real time. Preliminary calculation of the maximum size of collections will help to avoid unnecessary allocations.
The use of object pools is an industry standard for mobile development and allows you to completely eliminate garbage collection in critical sections of the code.
Testing, debugging and final assembly
After rewriting the main modules, the intensive stage begins testing. Automated unit tests will help ensure that the refactoring does not break existing functionality. Pay special attention to testing on real devices with different characteristics, and not just on an emulator.
Use debugging tools such as ADB Logcatto track errors in real time. The command adb logcat -v time will allow you to see the timestamps of events, which is useful when searching for the causes of freezes. Test the game on devices with different amounts of RAM and versions Android OS.
The final build must be performed with optimization flags enabled (minifyEnabled true, shrinkResources true). This will remove unused code and resources, reducing the size of the APK file. Be sure to sign your application with a release key and test it through zipalign before publishing.
⚠️ Warning: Enable StrictMode during development to detect thread and disk access violations in the main thread, but disable it in the release build to avoid performance degradation.
Frequently asked questions (FAQ)
Is it worth completely rewriting the game to a new engine?
A complete transition to a new engine (for example, from a custom one to Unity or Unreal) is justified only if the current one the solution is technically outdated and does not support the required functions. In most cases, it is more effective to optimize the existing code, since a full port requires a huge investment of time and resources.
What is the best way to deal with freezes in Android games?
The main cause of freezes is garbage collection (GC). To combat them, use object pools, avoid creating objects in a loop Update and optimize the use of string operations. Also check the load on the main thread and move heavy calculations to background threads.
Do you need to support older versions of Android when refactoring?
It depends on your target audience. Support for very old versions (below Android 8.0) may limit the use of modern APIs and optimizations. It is recommended to analyze the statistics of your users' devices in Google Play Console and install the minimum version of the SDK that covers the majority of the active base.
Which tools are best suited for profiling?
Ideal for native development Android Studio Profiler. For games on engines, use the built-in profilers (Unity Profiler, Unreal Insights). Tools Perfetto for in-depth analysis of system traces and scheduler operation are also useful.