3 files changed, 37 insertions, 5 deletions
diff --git a/core/java/android/app/ActivityTransitionCoordinator.java b/core/java/android/app/ActivityTransitionCoordinator.java
index d0d9d71..e3b27b5 100644
--- a/core/java/android/app/ActivityTransitionCoordinator.java
+++ b/core/java/android/app/ActivityTransitionCoordinator.java
@@ -799,6 +799,15 @@ abstract class ActivityTransitionCoordinator extends ResultReceiver {
         mIsStartingTransition = false;
     }
 
+    /**
+     * Cancels any pending transitions and returns true if there is a transition is in
+     * the middle of starting.
+     */
+    protected boolean cancelPendingTransitions() {
+        mPendingTransition = null;
+        return mIsStartingTransition;
+    }
+
     protected void moveSharedElementsToOverlay() {
         if (mWindow == null || !mWindow.getSharedElementsUseOverlay()) {
             return;
diff --git a/core/java/android/app/ActivityTransitionState.java b/core/java/android/app/ActivityTransitionState.java
index 555d20b..a2bfa4e 100644
--- a/core/java/android/app/ActivityTransitionState.java
+++ b/core/java/android/app/ActivityTransitionState.java
@@ -22,6 +22,7 @@ import android.util.ArrayMap;
 import android.util.SparseArray;
 import android.view.View;
 import android.view.ViewGroup;
+import android.view.ViewTreeObserver;
 import android.view.Window;
 
 import java.lang.ref.WeakReference;
@@ -252,7 +253,7 @@ class ActivityTransitionState {
         }
     }
 
-    public boolean startExitBackTransition(Activity activity) {
+    public boolean startExitBackTransition(final Activity activity) {
         if (mEnteringNames == null) {
             return false;
         } else {
@@ -260,10 +261,11 @@ class ActivityTransitionState {
                 mHasExited = true;
                 Transition enterViewsTransition = null;
                 ViewGroup decor = null;
+                boolean delayExitBack = false;
                 if (mEnterTransitionCoordinator != null) {
                     enterViewsTransition = mEnterTransitionCoordinator.getEnterViewsTransition();
                     decor = mEnterTransitionCoordinator.getDecor();
-                    mEnterTransitionCoordinator.cancelEnter();
+                    delayExitBack = mEnterTransitionCoordinator.cancelEnter();
                     mEnterTransitionCoordinator = null;
                     if (enterViewsTransition != null && decor != null) {
                         enterViewsTransition.pause(decor);
@@ -275,7 +277,23 @@ class ActivityTransitionState {
                 if (enterViewsTransition != null && decor != null) {
                     enterViewsTransition.resume(decor);
                 }
-                mReturnExitCoordinator.startExit(activity.mResultCode, activity.mResultData);
+                if (delayExitBack && decor != null) {
+                    final ViewGroup finalDecor = decor;
+                    decor.getViewTreeObserver().addOnPreDrawListener(
+                            new ViewTreeObserver.OnPreDrawListener() {
+                                @Override
+                                public boolean onPreDraw() {
+                                    finalDecor.getViewTreeObserver().removeOnPreDrawListener(this);
+                                    if (mReturnExitCoordinator != null) {
+                                        mReturnExitCoordinator.startExit(activity.mResultCode,
+                                                activity.mResultData);
+                                    }
+                                    return true;
+                                }
+                            });
+                } else {
+                    mReturnExitCoordinator.startExit(activity.mResultCode, activity.mResultData);
+                }
             }
             return true;
         }
diff --git a/core/java/android/app/EnterTransitionCoordinator.java b/core/java/android/app/EnterTransitionCoordinator.java
index ecf19c7..c053c83 100644
--- a/core/java/android/app/EnterTransitionCoordinator.java
+++ b/core/java/android/app/EnterTransitionCoordinator.java
@@ -18,7 +18,6 @@ package android.app;
 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.animation.ObjectAnimator;
-import android.graphics.Matrix;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.os.ResultReceiver;
@@ -565,7 +564,12 @@ class EnterTransitionCoordinator extends ActivityTransitionCoordinator {
         clearState();
     }
 
-    public void cancelEnter() {
+    /**
+     * Cancels the enter transition.
+     * @return True if the enter transition is still pending capturing the target state. If so,
+     * any transition started on the decor will do nothing.
+     */
+    public boolean cancelEnter() {
         setGhostVisibility(View.INVISIBLE);
         mHasStopped = true;
         mIsCanceled = true;
@@ -576,6 +580,7 @@ class EnterTransitionCoordinator extends ActivityTransitionCoordinator {
         }
         mActivity = null;
         clearState();
+        return super.cancelPendingTransitions();
     }
 
     private void makeOpaque() {