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Papon Ahasan
Papon Ahasan

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Memory Leaks

🧠 When Can Memory Leaks Happen?

Memory leaks in Android typically happen when an object that holds a reference to a Context (especially Activity) outlives its lifecycle, preventing the system from garbage collecting the Activity.

🧩 Types of Context and When to Use Which

✅ đŸšĢ Avoid Memory Leaks with These Tips

✅ 1. Use applicationContext when:

  • You don’t need to access UI

  • You're working in long-lived classes: e.g., repositories, databases, analytics trackers

val context = context.applicationContext
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✅ 2. Avoid Anonymous Inner Classes in Activities

Use static classes or top-level classes to avoid holding implicit references to Activities.

✅ 3. Clear Resources in Lifecycle

Always clear:

  • Observers (LiveData, BroadcastReceiver)

  • Coroutine scopes (Job.cancel())

  • Ad SDKs (nativeAd.destroy())

✅ 4. Don’t Hold Context in Singletons

If you must, store applicationContext, not Activity.

class MySingleton private constructor(private val context: Context) { companion object { fun init(appContext: Context): MySingleton { return MySingleton(appContext.applicationContext) } } }
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  1. Holding a reference to an Activity or View in a Singleton ❌ Problem: 
object MyManager { var context: Context? = null // holding activity context }
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📌 Real-World Example:

You create a singleton for analytics or ads that stores an Activity context to show a Toast or dialog — but forget to clear it.

✅ Solution:

Always use context.applicationContext in singletons.

context = context.applicationContext
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  1. Inner classes or anonymous classes (e.g. Runnable, Listener) holding implicit reference to outer Activity

❌ Problem:

class MyActivity : AppCompatActivity() { private val handler = Handler(Looper.getMainLooper()) fun start() { handler.postDelayed({ // 'this' refers to Activity, leak if Activity is destroyed }, 10000) } }
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✅ Solution:

Make the runnable a static class or cancel delayed tasks in onDestroy().

override fun onDestroy() { super.onDestroy() handler.removeCallbacksAndMessages(null) }
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  1. Long-running background tasks (Coroutines, AsyncTask, Threads) holding context

❌ Problem:

You start a coroutine in a ViewModel or plain class and hold an Activity context.

fun loadData(context: Context) { CoroutineScope(Dispatchers.IO).launch { // Holding context across configuration change or after activity is gone val db = DB.getInstance(context) } }
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✅ Solution:

  • Pass applicationContext if needed.
  • Cancel coroutine on lifecycle. 
fun loadData(appContext: Context) { CoroutineScope(Dispatchers.IO).launch { val db = DB.getInstance(appContext) } }
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  1. LiveData or Flow observing with lifecycle issues

❌ Problem:

You observe LiveData from ViewModel in a Context-based class (like a custom manager), not tied to lifecycle.

viewModel.data.observeForever { // Forever means it never stops -> leak }
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✅ Solution:

Always observe with LifecycleOwner (Activity or Fragment) unless you manually remove observers.

viewModel.data.observe(viewLifecycleOwner) { ... }
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  1. Dialogs or Toasts shown after Activity is destroyed ❌ Problem: 
fun showDialog(context: Context) { AlertDialog.Builder(context) .setMessage("Hello") .show() }
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If context is an Activity and it’s already finishing, the window leaks.
✅ Solution:

Check context:

if (context is Activity && !context.isFinishing) { AlertDialog.Builder(context) .setMessage("Safe") .show() }
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  1. Static Views or holding binding in fragments after view is destroyed ❌ Problem: 
class MyFragment : Fragment() { private lateinit var binding: FragmentMyBinding override fun onDestroyView() { super.onDestroyView() // Forget to clear binding -> view leak } }
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✅ Solution:

Clear binding in onDestroyView():

override fun onDestroyView() { super.onDestroyView() _binding = null }
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  1. Custom callbacks or listeners not removed ❌ Problem: 
someView.setOnClickListener { // Holds reference to outer Activity }
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If the view lives longer (e.g., part of an SDK), it keeps the activity alive.
✅ Solution:

Remove listeners:

override fun onDestroy() { someView.setOnClickListener(null) }
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class MySingleton private constructor(private val context: Context) { companion object { @Volatile private var INSTANCE: MySingleton? = null fun getInstance(appContext: Context): MySingleton { return INSTANCE ?: synchronized(this) { INSTANCE ?: MySingleton(appContext.applicationContext).also { INSTANCE = it } } } } // Example usage of application context fun doSomethingGlobal() { Toast.makeText(context, "Doing something!", Toast.LENGTH_SHORT).show() } }
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private var weakActivity: WeakReference<Activity>? = null fun bindActivity(activity: Activity) { weakActivity = WeakReference(activity) } fun doSomething() { val activity = weakActivity?.get() ?: return // Use it safely }
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❌ Problem: 🔴 Without Job — āĻ¸āĻŽāĻ¸ā§āĻ¯āĻž:

👉 āĻ¯āĻĻāĻŋ user ā§Ē āĻ¸ā§‡āĻ•ā§‡āĻ¨ā§āĻĄā§‡āĻ° āĻŽāĻ§ā§āĻ¯ā§‡ āĻŦāĻžāĻ°āĻŦāĻžāĻ° call āĻ•āĻ°ā§‡, āĻ¸āĻŦ coroutine queue āĻ¤ā§‡ āĻĸā§āĻ•ā§‡ āĻ¯āĻžāĻŦā§‡ → multiple popups → đŸ˜ĩ UI bug!

lifecycleScope.launch { delay(4000) getDrugDetailPopupImage(genericId) }
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đŸŸĸ With Job — Smart & Controlled: 👉 āĻāĻ•āĻŦāĻžāĻ°ā§‡ āĻļā§āĻ§ā§āĻŽāĻžāĻ¤ā§āĻ° āĻāĻ•āĻŸāĻž popup āĻšāĻ˛āĻŦā§‡āĨ¤ āĻ¨āĻ¤ā§āĻ¨ āĻ•āĻžāĻœ āĻāĻ˛ā§‡ āĻĒā§āĻ°āĻ¨ā§‹āĻŸāĻž āĻ•ā§‡āĻŸā§‡ āĻ¯āĻžāĻŦā§‡āĨ¤

private var popupJob: Job? = null popupJob?.cancel() // āĻĒā§āĻ°āĻ¨ā§‹ āĻšāĻ˛āĻŽāĻžāĻ¨ coroutine āĻŦāĻ¨ā§āĻ§ popupJob = lifecycleScope.launch { delay(4000) getDrugDetailPopupImage(genericId) }
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📌 āĻāĻ° āĻ‰āĻĻā§āĻĻā§‡āĻļā§āĻ¯:

  • āĻ†āĻ—ā§‡āĻ° popup coroutine āĻšāĻ˛āĻŽāĻžāĻ¨ āĻĨāĻžāĻ•āĻ˛ā§‡ āĻ¤āĻž cancel āĻ•āĻ°ā§‡ āĻĢā§‡āĻ˛āĻž
  • āĻ¨āĻ¤ā§āĻ¨ coroutine āĻĻāĻŋā§Ÿā§‡ popup image delayed show āĻ•āĻ°āĻž
  • āĻāĻ•āĻ‡ āĻ¸āĻŽā§Ÿ āĻāĻ•āĻŸāĻŋāĻ° āĻŦā§‡āĻļāĻŋ popup āĻ¨āĻž āĻĻā§‡āĻ–āĻžāĻ¨ā§‹
  • 🧠 Memory leak āĻ°ā§‹āĻ§ āĻ¨āĻž āĻšāĻžāĻ‡āĻ¤ā§‡āĻ“ āĻšāĻ˛āĻ¤ā§‡ āĻĨāĻžāĻ•āĻž coroutine āĻŦāĻ¨ā§āĻ§ āĻ•āĻ°ā§‡ āĻĻā§‡

āĻŽā§‡āĻŽā§‹āĻ°āĻŋ āĻ˛āĻŋāĻ• āĻ•ā§€?

āĻŽā§‡āĻŽā§‹āĻ°āĻŋ āĻ˛āĻŋāĻ• āĻ¤āĻ–āĻ¨ āĻšā§Ÿ, āĻ¯āĻ–āĻ¨ āĻ†āĻĒāĻ¨āĻžāĻ° āĻ…ā§āĻ¯āĻžāĻĒā§‡āĻ° āĻ…āĻŦāĻœā§‡āĻ•ā§āĻŸāĻ—ā§āĻ˛ā§‹ āĻ—āĻžāĻ°āĻŦā§‡āĻœ āĻ•āĻžāĻ˛ā§‡āĻ•ā§āĻŸāĻ° (Garbage Collector) āĻ°āĻŋāĻŽā§āĻ­ āĻ•āĻ°āĻ¤ā§‡ āĻĒāĻžāĻ°ā§‡ āĻ¨āĻž, āĻ•āĻžāĻ°āĻŖ āĻāĻ–āĻ¨āĻ“ āĻ•ā§‡āĻ‰ āĻ¸ā§‡āĻ‡ āĻ…āĻŦāĻœā§‡āĻ•ā§āĻŸā§‡āĻ° āĻ°ā§‡āĻĢāĻžāĻ°ā§‡āĻ¨ā§āĻ¸ āĻ§āĻ°ā§‡ āĻ°ā§‡āĻ–ā§‡āĻ›ā§‡ — āĻ¯āĻĻāĻŋāĻ“ āĻ¸ā§‡āĻ‡ āĻ…āĻŦāĻœā§‡āĻ•ā§āĻŸ āĻĻāĻ°āĻ•āĻžāĻ° āĻ¨ā§‡āĻ‡āĨ¤ āĻĢāĻ˛ā§‡ āĻ…ā§āĻ¯āĻžāĻĒā§‡āĻ° RAM āĻŦā§āĻ¯āĻŦāĻšāĻžāĻ° āĻŦāĻžā§œā§‡, āĻĒāĻžāĻ°āĻĢāĻ°āĻŽā§āĻ¯āĻžāĻ¨ā§āĻ¸ āĻ•āĻŽā§‡, āĻāĻŽāĻ¨āĻ•āĻŋ āĻ…ā§āĻ¯āĻžāĻĒ āĻ•ā§āĻ°ā§āĻ¯āĻžāĻļāĻ“ āĻ•āĻ°āĻ¤ā§‡ āĻĒāĻžāĻ°ā§‡āĨ¤

LeakCanary āĻšāĻ˛ Square āĻ•ā§‹āĻŽā§āĻĒāĻžāĻ¨āĻŋāĻ° āĻŦāĻžāĻ¨āĻžāĻ¨ā§‹ āĻāĻ•āĻŸāĻž open-source Android library āĻ¯āĻž āĻŽā§‡āĻŽā§‹āĻ°āĻŋ āĻ˛āĻŋāĻ• āĻ…āĻŸā§‹ āĻĄāĻŋāĻŸā§‡āĻ•ā§āĻŸ āĻ•āĻ°āĻ¤ā§‡ āĻĒāĻžāĻ°ā§‡ āĻĄā§‡āĻ­ā§‡āĻ˛āĻĒāĻŽā§‡āĻ¨ā§āĻŸ āĻŦāĻŋāĻ˛ā§āĻĄā§‡āĨ¤

// build.gradle (app) dependencies { debugImplementation "com.squareup.leakcanary:leakcanary-android:2.13" }
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Leak Report āĻĻā§‡āĻ–āĻ¤ā§‡ āĻ•ā§‡āĻŽāĻ¨ āĻšā§Ÿ?

// ➡ī¸ āĻāĻ‡ report āĻŦāĻ˛āĻ›ā§‡ MyActivity destroy āĻšāĻ“ā§ŸāĻžāĻ° āĻĒāĻ°ā§‡āĻ“ mContext āĻ°ā§‡āĻĢāĻžāĻ°ā§‡āĻ¨ā§āĻ¸ā§‡ āĻĨāĻžāĻ•āĻžāĻ° āĻ•āĻžāĻ°āĻŖā§‡ release āĻšā§ŸāĻ¨āĻŋāĨ¤ ActivityLeakActivity has leaked: â†ŗ xyz.MyActivity instance | mContext → xyz.MyActivity | mDestroyed → true
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Tip1: Leak Canary Debug Log:

D LeakCanary: Watching instance of xyz.MyActivity (Activity) with key XYZ123...
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â”Ŧ ├─ com.example.MyActivity │ Leaking: YES │ Retaining 1.2 MB in 10060 bytes │ ↓ MyActivity.someStaticReference │ ~~~~~~~~~~~~~ ├─ android.widget.SomeView │ ↓ View.mContext │ ~~~~~~~~ ...
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- MyFragment.binding null āĻ•āĻ°āĻž āĻšā§ŸāĻ¨āĻŋ, āĻ¤āĻžāĻ‡ View āĻāĻ° āĻŽāĻ§ā§āĻ¯ā§‡ āĻĨāĻžāĻ•āĻž context (Activity) leak āĻšā§Ÿā§‡āĻ›ā§‡āĨ¤ ✅ āĻ¸āĻŽāĻžāĻ§āĻžāĻ¨: onDestroyView() āĻ binding = null āĻ•āĻ°ā§‡ āĻĻāĻŋāĻ¨āĨ¤ â”Ŧ ├─ MyFragment │ Leaking: YES │ ↓ MyFragment.binding │ ~~~~~~~ ├─ MyFragmentBinding │ ↓ binding.textView │ ~~~~~~~~ ├─ TextView │ ↓ View.mContext │ ~~~~~~~
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āĻĒā§āĻ°āĻ¤āĻŋāĻŸāĻŋ āĻ˛āĻžāĻ‡āĻ¨ āĻĻā§‡āĻ–ā§āĻ¨ āĻ¯ā§‡āĻŸāĻžāĻ¤ā§‡ ↓ (down arrow) āĻ†āĻ›ā§‡, LeakCanary āĻāĻ‡ arrows āĻĻāĻŋā§Ÿā§‡ āĻŦā§‹āĻāĻžā§Ÿ āĻ•āĻžāĻ° āĻŽāĻžāĻ§ā§āĻ¯āĻŽā§‡ āĻ°ā§‡āĻĢāĻžāĻ°ā§‡āĻ¨ā§āĻ¸ āĻ§āĻ°ā§‡ āĻ†āĻ›ā§‡:

StrictMode.setThreadPolicy( StrictMode.ThreadPolicy.Builder() .detectDiskReads() // āĻĄāĻŋāĻ¸ā§āĻ• āĻĨā§‡āĻ•ā§‡ āĻĄāĻžāĻŸāĻž āĻĒā§œāĻž āĻšāĻ˛ā§‡ āĻ¸āĻ¤āĻ°ā§āĻ• āĻ•āĻ°āĻŦā§‡ .detectDiskWrites() // āĻĄāĻŋāĻ¸ā§āĻ•ā§‡ āĻ˛ā§‡āĻ–āĻž āĻšāĻ˛ā§‡ āĻ¸āĻ¤āĻ°ā§āĻ• āĻ•āĻ°āĻŦā§‡ .detectNetwork() // āĻ¨ā§‡āĻŸāĻ“ā§ŸāĻžāĻ°ā§āĻ• āĻ•āĻ˛ āĻšāĻ˛ā§‡ āĻ¸āĻ¤āĻ°ā§āĻ• āĻ•āĻ°āĻŦā§‡ .penaltyLog() // āĻāĻ¸āĻŦ āĻ˜āĻŸāĻ¨āĻžāĻ° āĻ¸āĻŽā§Ÿ āĻ˛āĻ— āĻ•āĻ°āĻŦā§‡ .build() ) StrictMode.setVmPolicy( StrictMode.VmPolicy.Builder() .detectLeakedSqlLiteObjects() // āĻ¯ā§‡āĻ¸āĻŦ Sqlite āĻ…āĻŦāĻœā§‡āĻ•ā§āĻŸ āĻŦāĻ¨ā§āĻ§ āĻšā§ŸāĻ¨āĻŋ, āĻ¸ā§‡āĻ—ā§āĻ˛ā§‹ āĻšāĻŋāĻ¨āĻŦā§‡ .detectLeakedClosableObjects() // āĻ¯ā§‡āĻ¸āĻŦ āĻ•ā§āĻ˛ā§‹āĻœā§‡āĻŦāĻ˛ āĻ…āĻŦāĻœā§‡āĻ•ā§āĻŸ (āĻ¯ā§‡āĻŽāĻ¨ āĻĢāĻžāĻ‡āĻ˛, āĻ¸ā§āĻŸā§āĻ°ā§€āĻŽ) āĻŦāĻ¨ā§āĻ§ āĻšā§ŸāĻ¨āĻŋ āĻ¸ā§‡āĻ—ā§āĻ˛ā§‹ āĻšāĻŋāĻ¨āĻŦā§‡ .penaltyLog() // āĻāĻ¸āĻŦ āĻ‡āĻ¸ā§āĻ¯ā§ āĻšāĻ˛ā§‡ āĻ˛āĻ— āĻ•āĻ°āĻŦā§‡ .build() ) - āĻŽā§‡āĻ‡āĻ¨ āĻĨā§āĻ°ā§‡āĻĄā§‡ āĻĄāĻŋāĻ¸ā§āĻ• āĻŦāĻž āĻ¨ā§‡āĻŸāĻ“ā§ŸāĻžāĻ°ā§āĻ• āĻ…āĻĒāĻžāĻ°ā§‡āĻļāĻ¨ āĻšāĻ˛ā§‡ āĻ¤ā§‹āĻŽāĻžāĻ•ā§‡ āĻœāĻžāĻ¨āĻžāĻŦā§‡ - āĻ¯ā§‡āĻ¸āĻŦ āĻĄā§‡āĻŸāĻžāĻŦā§‡āĻ¸ āĻŦāĻž āĻĢāĻžāĻ‡āĻ˛ āĻ°āĻŋāĻ¸ā§‹āĻ°ā§āĻ¸ āĻ¤ā§āĻŽāĻŋ āĻ­ā§āĻ˛ā§‡ āĻŦāĻ¨ā§āĻ§ āĻ•āĻ°ā§‹ āĻ¨āĻŋ, āĻ¸ā§‡āĻ—ā§āĻ˛ā§‹āĻ“ āĻ§āĻ°āĻŦā§‡ - āĻ¸āĻŦāĻ‡ āĻ˛āĻ— āĻ•āĻ°ā§‡ āĻĄā§‡āĻ­ā§‡āĻ˛āĻĒāĻžāĻ°āĻ•ā§‡ āĻ‡āĻ¸ā§āĻ¯ā§ āĻ¸āĻŽā§āĻĒāĻ°ā§āĻ•ā§‡ āĻ¸āĻšā§‡āĻ¤āĻ¨ āĻ•āĻ°āĻŦā§‡ āĻ•ā§‡āĻ¨ āĻĻāĻ°āĻ•āĻžāĻ°? āĻ…ā§āĻ¯āĻžāĻĒ āĻ āĻŋāĻ•āĻ āĻžāĻ• āĻāĻŦāĻ‚ āĻĻā§āĻ°ā§āĻ¤ āĻ•āĻžāĻœ āĻ•āĻ°ā§āĻ• āĻ†āĻ° āĻ‡āĻ‰āĻœāĻžāĻ° āĻ­āĻžāĻ˛ā§‹ āĻ…āĻ­āĻŋāĻœā§āĻžāĻ¤āĻž āĻĒāĻžā§Ÿ, āĻ¸ā§‡āĻœāĻ¨ā§āĻ¯ āĻ¯ā§‡āĻ¸āĻŦ āĻ•āĻžāĻœ āĻŽā§‡āĻ‡āĻ¨ āĻĨā§āĻ°ā§‡āĻĄ āĻŦā§āĻ˛āĻ• āĻ•āĻ°ā§‡ āĻ¸ā§‡āĻ—ā§āĻ˛ā§‹ āĻ–ā§āĻāĻœā§‡ āĻŦā§‡āĻ° āĻ•āĻ°āĻž āĻ–ā§āĻŦ āĻœāĻ°ā§āĻ°āĻŋāĨ¤ StrictMode āĻ¸ā§‡āĻ‡ āĻ•āĻžāĻœā§‡ āĻ¸āĻžāĻšāĻžāĻ¯ā§āĻ¯ āĻ•āĻ°ā§‡āĨ¤
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