A sample project to demonstrate memory leak issues in the Android Support Library when using Fragments in combination with the Loader API.

• Since version 24.0.0 of the support library, a Fragment using a Loader which is detached will leak the Activity through the LoaderManager. Fragments are usually detached when switching between sections inside an app or when swiping in a ViewPager using a FragmentPagerAdapter.

• Since way before that (maybe since forever), a Fragment using a Loader with setRetainInstance(true) will leak the Activity through the LoaderManager. The fragment does not need to be detached for the leak to occur.

• Launch this project on any device
• Press the button to detach the fragment
• Rotate the screen to trigger a configuration change
• In the Memory Monitor in Android Studio, initiate a few garbage collections then press the button to dump the Java heap.
• In the heap analyzer, look for the MainActivity class and notice there are two instances of it in memory instead of one.

Using the LeakCanary library from Square, the leak can be traced back to a variable named mHost in LoadermanagerImpl:

In be.digitalia.sample.fragmentleaks:1.0:1.
* be.digitalia.sample.fragmentleaks.MainActivity has leaked:
* GC ROOT static android.view.WindowManagerGlobal.sDefaultWindowManager
* references android.view.WindowManagerGlobal.mRoots
* references java.util.ArrayList.array
* references array java.lang.Object[].[0]
* references android.view.ViewRootImpl.mContext
* references be.digitalia.sample.fragmentleaks.MainActivity.mFragments
* references android.support.v4.app.FragmentController.mHost
* references android.support.v4.app.FragmentActivity$HostCallbacks.mAllLoaderManagers
* references android.support.v4.util.SimpleArrayMap.mArray
* references array java.lang.Object[].[1]
* references android.support.v4.app.LoaderManagerImpl.mHost
* references android.support.v4.app.FragmentActivity$HostCallbacks.this$0
* leaks be.digitalia.sample.fragmentleaks.MainActivity instance

Both issues produce the same leak trace so they seem to be caused by the same bug.