Clear child FragmentManagers when destroying Fragments.

If Fragment has instantiated a child FragmentManager and is later
detached, it retains its reference to the child FragmentManager which
has been destroyed. This causes an IllegalStateException in the
child FragmentManager if the original Fragment is reattached.

Fixes Issue 42601.

Change-Id: I8db2b1a110a341dc259939723f4c5ec131ca5f1e

2 files changed, 2 insertions, 0 deletions

diff --git a/core/java/android/app/Fragment.java b/core/java/android/app/Fragment.java
index d626e5f..af8f177 100644
--- a/core/java/android/app/Fragment.java
+++ b/core/java/android/app/Fragment.java
@@ -1402,6 +1402,7 @@ public class Fragment implements ComponentCallbacks2, OnCreateContextMenuListene
         mRestored = false;
         mBackStackNesting = 0;
         mFragmentManager = null;
+        mChildFragmentManager = null;
         mActivity = null;
         mFragmentId = 0;
         mContainerId = 0;
diff --git a/core/java/android/app/FragmentManager.java b/core/java/android/app/FragmentManager.java
index bf2a629..76f9d97 100644
--- a/core/java/android/app/FragmentManager.java
+++ b/core/java/android/app/FragmentManager.java
@@ -1026,6 +1026,7 @@ final class FragmentManagerImpl extends FragmentManager {
                                     f.mActivity = null;
                                     f.mParentFragment = null;
                                     f.mFragmentManager = null;
+                                    f.mChildFragmentManager = null;
                                 }
                             }
                         }