Null check for fade start alpha value.

Bug 27105186
Fade previously hadn't had any values saved over those captured
by Visibility. If a Transition merged two Visibility transitions,
it could avoid calling captureStartValues for the Fade transition.
This change prevents an NPE in that case. The combined transition
won't get the intermediate alpha value, but at least it won't
crash.

Change-Id: I8e5720caafda56b017dfe1cc0b16ebdf246e90c4

1 files changed, 16 insertions, 11 deletions

diff --git a/core/java/android/transition/Fade.java b/core/java/android/transition/Fade.java
index b2e8d3351028..627183f0cf24 100644
--- a/core/java/android/transition/Fade.java
+++ b/core/java/android/transition/Fade.java
@@ -16,8 +16,6 @@
 
 package android.transition;
 
-import com.android.internal.R;
-
 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.animation.ObjectAnimator;
@@ -28,6 +26,8 @@ import android.util.Log;
 import android.view.View;
 import android.view.ViewGroup;
 
+import com.android.internal.R;
+
 /**
  * This transition tracks changes to the visibility of target views in the
  * start and end scenes and fades views in or out when they become visible
@@ -144,12 +144,9 @@ public class Fade extends Visibility {
             Log.d(LOG_TAG, "Fade.onAppear: startView, startVis, endView, endVis = " +
                     startView + ", " + view);
         }
-        float startAlpha = 0;
-        if (startValues != null) {
-            startAlpha = (Float) startValues.values.get(PROPNAME_TRANSITION_ALPHA);
-            if (startAlpha == 1) {
-                startAlpha = 0;
-            }
+        float startAlpha = getStartAlpha(startValues, 0);
+        if (startAlpha == 1) {
+            startAlpha = 0;
         }
         return createAnimation(view, startAlpha, 1);
     }
@@ -157,11 +154,19 @@ public class Fade extends Visibility {
     @Override
     public Animator onDisappear(ViewGroup sceneRoot, final View view, TransitionValues startValues,
             TransitionValues endValues) {
-        float startAlpha = 1;
+        float startAlpha = getStartAlpha(startValues, 1);
+        return createAnimation(view, startAlpha, 0);
+    }
+
+    private static float getStartAlpha(TransitionValues startValues, float fallbackValue) {
+        float startAlpha = fallbackValue;
         if (startValues != null) {
-            startAlpha = (Float) startValues.values.get(PROPNAME_TRANSITION_ALPHA);
+            Float startAlphaFloat = (Float) startValues.values.get(PROPNAME_TRANSITION_ALPHA);
+            if (startAlphaFloat != null) {
+                startAlpha = startAlphaFloat;
+            }
         }
-        return createAnimation(view, startAlpha, 0);
+        return startAlpha;
     }
 
     private static class FadeAnimatorListener extends AnimatorListenerAdapter {