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Get rid of all Memory Leaks

Piotr Krystyniak

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Objects Graph

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Objects Graph

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Garbage Collection - mark live objects

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Garbage Collection - mark live objects

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Garbage Collection - sweep

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New Object Graph

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Memory leak?

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Part of memory which is not longer needed but is not released

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Graph with leaked activity

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Graph with leaked activity

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Graph with leaked activity

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Graph with leaked activity

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What causes memory leaks?

  • Registering callback to a singleton (f.e event bus) and not unregistering
  • Passing callback to a long running task or never-ending task and not canceling
  • RxJava - missing Subscription#unsubscribe()
  • In general - passing Context to Objects that live longer than that Context

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Example 1

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Example 2

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Example 3

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Example 3

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Always unsubscribe

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RecyclerView example

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RecyclerView example

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RecyclerView example

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RecyclerView example

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RecyclerView example

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  • LinearLayoutManager#setRecycleChildrenOnDetach(true); // false default
  • Each LayoutManager handles this differently

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WeakReference

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WeakReference

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WeakReference

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WeakReference

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WeakReference

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WeakReference

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SDK have leaks

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How to find a memory leak?

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LeakCanary

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LeakCanary

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LeakCanary

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LeakCanary - upload leak report

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Android Studio Memory Analyzer

  • Works with heap dumps (hprof file)
  • Allows to inspect all objects and their references

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Summary

  • Don’t pass Context to objects living longer than Context
  • Always unregister/unsubscribe
  • Check if unregister/unsubscribe is really called
  • Use WeakReference if you must
  • Use tracking tools
  • Memory leaks are like bugs, there is no general approach to solve them

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Questions?