Is it possible to make any application start quickly?

Fast app startup is a desirable but not always fully achievable goal in practice, heavily dependent on many factors.

Key principles and techniques for optimizing startup speed:

1. Minimize work on the main (UI) thread:

   • Deferred initialization of components.
   • Use background threads for resource-intensive operations (e.g., data loading, database work).
   • Lazy loading of View elements.

2. Resource optimization:

   • Use vector graphics instead of raster images when possible.
   • Compress images.
   • Optimize layouts (reduce nesting, use ConstraintLayout).

3. Use App Startup Library:

   • Allows defining the order of component initialization at startup and doing it efficiently.

   // Example of declaring an initializer in AndroidManifest.xml
   <provider
       android:name="androidx.startup.InitializationProvider"
       android:authorities="${applicationId}.androidx-startup"
       android:exported="false"
       tools:node="merge">
       <!-- This entry makes SampleLibraryInitializer discoverable. -->
       <meta-data android:name="com.example.MyInitializer"
           android:value="androidx.startup" />
   </provider>
   

   // Example of MyInitializer class
   class MyInitializer : Initializer<MyLibrary> {
       override fun create(context: Context): MyLibrary {
           // Initialize the library
           return MyLibrary(context)
       }
   
       override fun dependencies(): List<Class<out Initializer<*>>> {
           // List of dependencies to be initialized earlier
           return emptyList()
       }
   }
   

4. Performance analysis:

   • Use Android Profiler tools (CPU, Memory, Network) to identify bottlenecks.
   • Use Perfetto or Systrace for more detailed system event analysis.

5. Profiling at startup:

   • Use Application.onCreate() to measure execution time.
   • Log steps that take a lot of time.

   // Example of logging execution time
   long startTime = System.currentTimeMillis();
   super.onCreate();
   // Initialize components...
   long endTime = System.currentTimeMillis();
   Log.d("AppStart", "Application onCreate took: " + (endTime - startTime) + " ms");
   

6. Optimize APK/App Bundle size:

   • Remove unused code and resources (using ProGuard/R8).
   • Split APK by architectures (ABI splits).

7. Network operations:

   • Do not block the main thread with network requests during startup.
   • Cache data.

Despite these techniques, startup speed can depend on:

• Device performance.
• System state (CPU load, free RAM).
• Number of installed apps and their activity.
• Complexity of app initialization (amount of data to load, number of libraries).

A fully "instant" startup may be unrealistic, but you can achieve the fastest and most responsive operation through sequential optimization.