Android Studio version

The bug is currently still present on the main branch at https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main

Root cause

RootsDetector.lastRootIds, which is a Set<Long>, accidentally references all the root views by building that set using RootsDetector.getRootViewsOnMainThread().keys which doesn't create a new set and under the hood keeps a reference to the map of view uniqueDrawingId to views.

Here's what the current code is doing:

val currRoots = WindowInspector.getGlobalWindowViews()
  .filter { view -> view.visibility == View.VISIBLE && view.isAttachedToWindow }
  .sortedBy { view -> view.z }
  .associateBy { it.uniqueDrawingId }
RootsDetector.lastRootIds = currRoots.keys

While RootsDetector.lastRootIds is a Set<Long>, the implementation keeps a reference to currRoots. See Leak Trace below:

Leak Trace

┬───
│ GC Root: Local variable in native code
│
├─ com.android.tools.agent.app.inspection.AppInspectionService instance
│    ↓ AppInspectionService.mInspectorBridges
│                           ~~~~~~~~~~~~~~~~~
├─ java.util.concurrent.ConcurrentHashMap instance
│    ↓ ConcurrentHashMap["layoutinspector.view.inspection"]
│                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
├─ com.android.tools.agent.app.inspection.InspectorBridge instance
│    ↓ InspectorBridge.mInspectorContext
│                      ~~~~~~~~~~~~~~~~~
├─ com.android.tools.agent.app.inspection.InspectorContext instance
│    ↓ InspectorContext.mInspector
│                       ~~~~~~~~~~
├─ com.android.tools.agent.appinspection.ViewLayoutInspector instance
│    ↓ ViewLayoutInspector.rootsDetector
│                          ~~~~~~~~~~~~~
├─ com.android.tools.agent.appinspection.RootsDetector instance
│    ↓ RootsDetector.lastRootIds
│                    ~~~~~~~~~~~
├─ java.util.LinkedHashMap$LinkedKeySet instance
│    ↓ LinkedHashMap$LinkedKeySet.this$0
│                                 ~~~~~~
├─ java.util.LinkedHashMap instance
│    ↓ LinkedHashMap[java.lang.Long]
│                   ~~~~~~~~~~~~~~~~
╰→ com.android.internal.policy.DecorView instance
​     Leaking: YES (View.mContext references a destroyed activity)
​     View not part of a window view hierarchy
​     View.mAttachInfo is null (view detached)
​     View.mWindowAttachCount = 1
​     mContext instance of com.android.internal.policy.DecorContext, wrapping activity com.squareup.ui.loggedout.LoggedOutActivity with mDestroyed = true

Fix

Instead of referencing currRoots.keys, make a copy of that set into a new set of long.