Merge "Expose isStateSaved() in FragmentManager."

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);

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);

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);

core/java/android/app/Activity.java

@@ -2822,7 +2822,9 @@ public class Activity extends ContextThemeWrapper
             return;
         }
 
-        if (!mFragments.getFragmentManager().popBackStackImmediate()) {
+        FragmentManager fragmentManager = mFragments.getFragmentManager();
+
+        if (fragmentManager.isStateSaved() || !fragmentManager.popBackStackImmediate()) {
             finishAfterTransition();
         }
     }

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;
     }