From 27b0dc0287022ce7b644ec92d8de6f98e33a6c09 Mon Sep 17 00:00:00 2001
From: George Mount <mount@google.com>
Date: Tue, 21 Feb 2017 10:24:09 -0800
Subject: [PATCH] Expose isStateSaved() in FragmentManager.

Bug 35594367

Protect the FragmentManager during onBackPressed() from
changing the state after the state was saved.

Test: I15891a70699308eddda4e55fa0eb96064ffa7b17
Change-Id: I10f823801e85ca200351a64b14975c4421b9068b
---
 api/current.txt                            |  1 +
 api/system-current.txt                     |  1 +
 api/test-current.txt                       |  1 +
 core/java/android/app/Activity.java        |  4 +++-
 core/java/android/app/FragmentManager.java | 14 ++++++++++++++
 5 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/api/current.txt b/api/current.txt
index 6d71f441fdcfc..626cdae536636 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -4737,6 +4737,7 @@ package android.app {
     method public abstract android.app.Fragment getPrimaryNavigationFragment();
     method public void invalidateOptionsMenu();
     method public abstract boolean isDestroyed();
+    method public abstract boolean isStateSaved();
     method public abstract void popBackStack();
     method public abstract void popBackStack(java.lang.String, int);
     method public abstract void popBackStack(int, int);
diff --git a/api/system-current.txt b/api/system-current.txt
index 8413036182df4..0c042c3cd575d 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -4898,6 +4898,7 @@ package android.app {
     method public abstract android.app.Fragment getPrimaryNavigationFragment();
     method public void invalidateOptionsMenu();
     method public abstract boolean isDestroyed();
+    method public abstract boolean isStateSaved();
     method public abstract void popBackStack();
     method public abstract void popBackStack(java.lang.String, int);
     method public abstract void popBackStack(int, int);
diff --git a/api/test-current.txt b/api/test-current.txt
index 00a83394df36e..428594a7804a2 100644
--- a/api/test-current.txt
+++ b/api/test-current.txt
@@ -4747,6 +4747,7 @@ package android.app {
     method public abstract android.app.Fragment getPrimaryNavigationFragment();
     method public void invalidateOptionsMenu();
     method public abstract boolean isDestroyed();
+    method public abstract boolean isStateSaved();
     method public abstract void popBackStack();
     method public abstract void popBackStack(java.lang.String, int);
     method public abstract void popBackStack(int, int);
diff --git a/core/java/android/app/Activity.java b/core/java/android/app/Activity.java
index 6fc60e9eaaf22..95dc52dea79a1 100644
--- a/core/java/android/app/Activity.java
+++ b/core/java/android/app/Activity.java
@@ -2820,7 +2820,9 @@ public class Activity extends ContextThemeWrapper
             return;
         }
 
-        if (!mFragments.getFragmentManager().popBackStackImmediate()) {
+        FragmentManager fragmentManager = mFragments.getFragmentManager();
+
+        if (fragmentManager.isStateSaved() || !fragmentManager.popBackStackImmediate()) {
             finishAfterTransition();
         }
     }
diff --git a/core/java/android/app/FragmentManager.java b/core/java/android/app/FragmentManager.java
index 8ad7810a13e84..977931a66e1e0 100644
--- a/core/java/android/app/FragmentManager.java
+++ b/core/java/android/app/FragmentManager.java
@@ -396,6 +396,19 @@ public abstract class FragmentManager {
      */
     public void invalidateOptionsMenu() { }
 
+    /**
+     * Returns {@code true} if the FragmentManager's state has already been saved
+     * by its host. Any operations that would change saved state should not be performed
+     * if this method returns true. For example, any popBackStack() method, such as
+     * {@link #popBackStackImmediate()} or any FragmentTransaction using
+     * {@link FragmentTransaction#commit()} instead of
+     * {@link FragmentTransaction#commitAllowingStateLoss()} will change
+     * the state and will result in an error.
+     *
+     * @return true if this FragmentManager's state has already been saved by its host
+     */
+    public abstract boolean isStateSaved();
+
     /**
      * Callback interface for listening to fragment state changes that happen
      * within a given FragmentManager.
@@ -1787,6 +1800,7 @@ final class FragmentManagerImpl extends FragmentManager implements LayoutInflate
         }
     }
 
+    @Override
     public boolean isStateSaved() {
         return mStateSaved;
     }