Never drag scroll views with no children.

Fixes a regression from Froyo.  Previously, when a scroll view
had no children, its onTouchEvent would return because the scroll
view would only start dragging if the user touched one of its children.
In Gingerbread, the user can drag from anywhere within the scroll
view, not just by touching a child.  However, it makes no sense
to drag a scroll view that has no children so an empty scroll view
should just ignore touches like any other empty view group would.

This change fixes applications that for some reason or other happen
to have empty scroll views in strange places.

Bug: 3246230
Change-Id: Iada6e886e8363e6778f42fc4861de228512d8bed

2 files changed, 10 insertions, 6 deletions

diff --git a/core/java/android/widget/HorizontalScrollView.java b/core/java/android/widget/HorizontalScrollView.java
index f6b1dbc99b40..db22a0cb1e31 100644
--- a/core/java/android/widget/HorizontalScrollView.java
+++ b/core/java/android/widget/HorizontalScrollView.java
@@ -511,8 +511,10 @@ public class HorizontalScrollView extends FrameLayout {
 
         switch (action & MotionEvent.ACTION_MASK) {
             case MotionEvent.ACTION_DOWN: {
-                final float x = ev.getX();
-                mIsBeingDragged = true;
+                mIsBeingDragged = getChildCount() != 0;
+                if (!mIsBeingDragged) {
+                    return false;
+                }
 
                 /*
                  * If being flinged and user touches, stop the fling. isFinished
@@ -523,7 +525,7 @@ public class HorizontalScrollView extends FrameLayout {
                 }
 
                 // Remember where the motion event started
-                mLastMotionX = x;
+                mLastMotionX = ev.getX();
                 mActivePointerId = ev.getPointerId(0);
                 break;
             }
diff --git a/core/java/android/widget/ScrollView.java b/core/java/android/widget/ScrollView.java
index 8558c70e40de..ce6da72a2c98 100644
--- a/core/java/android/widget/ScrollView.java
+++ b/core/java/android/widget/ScrollView.java
@@ -521,8 +521,10 @@ public class ScrollView extends FrameLayout {
 
         switch (action & MotionEvent.ACTION_MASK) {
             case MotionEvent.ACTION_DOWN: {
-                final float y = ev.getY();
-                mIsBeingDragged = true;
+                mIsBeingDragged = getChildCount() != 0;
+                if (!mIsBeingDragged) {
+                    return false;
+                }
 
                 /*
                  * If being flinged and user touches, stop the fling. isFinished
@@ -537,7 +539,7 @@ public class ScrollView extends FrameLayout {
                 }
 
                 // Remember where the motion event started
-                mLastMotionY = y;
+                mLastMotionY = ev.getY();
                 mActivePointerId = ev.getPointerId(0);
                 break;
             }