Memory Leak: FileKitDialog._registry Retains Activity After Destruction

[DanielBulavinov]

Summary

FileKit library retains a reference to ActivityResultRegistry through a static field in FileKitDialog, preventing Android Activities from being garbage collected after they are destroyed.

Environment

• Library Version: filekit-core 0.12.0
• Platform: Android (iOS not tested)

Steps to Reproduce

1. Call FileKit.init(activity) on a screen
2. Navigate away from the screen or close the app
3. Activity remains in memory and is not garbage collected

Leak Trace

LeakCanary reports the following retention chain:

GC Root: Thread object
├─ android.net.ConnectivityThread instance
│    ↓ Thread.contextClassLoader
├─ dalvik.system.PathClassLoader instance
│    ↓ ClassLoader.runtimeInternalObjects
├─ java.lang.Object[] array
│    ↓ Object[3968]
├─ io.github.vinceglb.filekit.dialogs.FileKitDialog class
│    ↓ static FileKitDialog._registry
│                           ~~~~~~~~~
├─ androidx.activity.ComponentActivity$activityResultRegistry$1 instance
│    Retaining 615.5 kB in 12731 objects
│    Anonymous subclass of androidx.activity.result.ActivityResultRegistry
│    this$0 instance of com.vinted.carrier.MainActivity with mDestroyed = true
│    ↓ ComponentActivity$activityResultRegistry$1.this$0
│                                                 ~~~~~~
╰→ com.vinted.carrier.MainActivity instance
     Leaking: YES (ObjectWatcher was watching this because com.vinted.carrier.MainActivity received
     Activity#onDestroy() callback and Activity#mDestroyed is true)
     Retaining 608.6 kB in 12497 objects
     key = 9de4ea76-92f4-4034-9094-ec25f65f0546
     watchDurationMillis = 5546
     retainedDurationMillis = 530

Assumed Root Cause

The FileKitDialog object maintains a static reference to ActivityResultRegistry:

internal object FileKitDialog {
    private var _registry: ActivityResultRegistry? = null
    val registry: ActivityResultRegistry
        get() = _registry
            ?: throw FileKitNotInitializedException()

    fun init(registry: ActivityResultRegistry) {
        _registry = registry
    }
}

Assumed problem:

• FileKit.init(activity) sets FileKitDialog._registry = activity.activityResultRegistry
• The ActivityResultRegistry holds a reference to the Activity (this$0)
• The static _registry field persists for the lifetime of the class
• When the Activity is destroyed, the static reference prevents the ActivityResultRegistry from being garbage collected
• The ActivityResultRegistry retains the Activity, preventing it from being garbage collected
• There appears to be no cleanup mechanism to clear the _registry reference when the Activity is destroyed