Add a way to get Transitions from a TransitionSet.

Bug 17113732

Change-Id: I0a157a59448e66560ba2252709971131c5dea401

api/current.txt

@@ -32242,6 +32242,8 @@ package android.transition {
     method public void captureEndValues(android.transition.TransitionValues);
     method public void captureStartValues(android.transition.TransitionValues);
     method public int getOrdering();
+    method public android.transition.Transition getTransitionAt(int);
+    method public int getTransitionCount();
     method public android.transition.TransitionSet removeTransition(android.transition.Transition);
     method public android.transition.TransitionSet setOrdering(int);
     field public static final int ORDERING_SEQUENTIAL = 1; // 0x1

core/java/android/transition/TransitionSet.java

@@ -150,6 +150,31 @@ public class TransitionSet extends Transition {
         return this;
     }
 
+    /**
+     * Returns the number of child transitions in the TransitionSet.
+     *
+     * @return The number of child transitions in the TransitionSet.
+     * @see #addTransition(Transition)
+     * @see #getTransitionAt(int)
+     */
+    public int getTransitionCount() {
+        return mTransitions.size();
+    }
+
+    /**
+     * Returns the child Transition at the specified position in the TransitionSet.
+     *
+     * @param index The position of the Transition to retrieve.
+     * @see #addTransition(Transition)
+     * @see #getTransitionCount()
+     */
+    public Transition getTransitionAt(int index) {
+        if (index < 0 || index >= mTransitions.size()) {
+            return null;
+        }
+        return mTransitions.get(index);
+    }
+
     /**
      * Setting a non-negative duration on a TransitionSet causes all of the child
      * transitions (current and future) to inherit this duration.

policy/src/com/android/internal/policy/impl/PhoneWindow.java

@@ -3559,6 +3559,10 @@ public class PhoneWindow extends Window implements MenuBuilder.Callback {
         if (transitionId != -1 && transitionId != R.transition.no_transition) {
             TransitionInflater inflater = TransitionInflater.from(getContext());
             transition = inflater.inflateTransition(transitionId);
+            if (transition instanceof TransitionSet &&
+                    ((TransitionSet)transition).getTransitionCount() == 0) {
+                transition = null;
+            }
         }
         return transition;
     }