am fa21e757: Merge "Ensure views are attached prior to starting enter transition." into lmp-mr1-dev

* commit 'fa21e75734878a9718f85c7d3f28c5946f15d01d':
  Ensure views are attached prior to starting enter transition.

1 files changed, 5 insertions, 4 deletions

diff --git a/core/java/android/app/EnterTransitionCoordinator.java b/core/java/android/app/EnterTransitionCoordinator.java
index 7894887..ecf19c7 100644
--- a/core/java/android/app/EnterTransitionCoordinator.java
+++ b/core/java/android/app/EnterTransitionCoordinator.java
@@ -133,16 +133,17 @@ class EnterTransitionCoordinator extends ActivityTransitionCoordinator {
             return;
         }
         mAreViewsReady = true;
+        final ViewGroup decor = getDecor();
         // Ensure the views have been laid out before capturing the views -- we need the epicenter.
-        if (sharedElements.isEmpty() || !sharedElements.valueAt(0).isLayoutRequested()) {
+        if (decor == null || (decor.isAttachedToWindow() &&
+                (sharedElements.isEmpty() || !sharedElements.valueAt(0).isLayoutRequested()))) {
             viewsReady(sharedElements);
         } else {
-            final View sharedElement = sharedElements.valueAt(0);
-            sharedElement.getViewTreeObserver()
+            decor.getViewTreeObserver()
                     .addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
                 @Override
                 public boolean onPreDraw() {
-                    sharedElement.getViewTreeObserver().removeOnPreDrawListener(this);
+                    decor.getViewTreeObserver().removeOnPreDrawListener(this);
                     viewsReady(sharedElements);
                     return true;
                 }