In onLayout, only scroll if the content view is ready

Summary:
ScrollViews don't properly maintain position where they are hidden and shown. There is an edge case where on onLayout for a ScrollView, its content may not have been laid out yet. This happens in some cases when a scroll view is hidden via display: 'none' (resulting in setVisibility(INVISIBLE)). Check that the content view is laid out before attempting a scroll.

Changelog:
[Internal][Fixed] - In onLayout, only scroll if the content view is ready

Reviewed By: sshic

Differential Revision: D42794750

fbshipit-source-id: 654a380bcae306da2704d3e190423c8de125833d

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollView.java

@@ -356,14 +356,17 @@ protected void onLayout(boolean changed, int l, int t, int r, int b) {
       mScrollXAfterMeasure = NO_SCROLL_POSITION;
     }
 
-    // Call with the present values in order to re-layout if necessary
-    // If a "pending" value has been set, we restore that value.
-    // That value gets cleared by reactScrollTo.
-    int scrollToX =
-        pendingContentOffsetX != UNSET_CONTENT_OFFSET ? pendingContentOffsetX : getScrollX();
-    int scrollToY =
-        pendingContentOffsetY != UNSET_CONTENT_OFFSET ? pendingContentOffsetY : getScrollY();
-    scrollTo(scrollToX, scrollToY);
+    // Apply pending contentOffset in case it was set before the view was laid out.
+    if (isContentReady()) {
+      // If a "pending" content offset value has been set, we restore that value.
+      // Upon call to scrollTo, the "pending" values will be re-set.
+      int scrollToX =
+          pendingContentOffsetX != UNSET_CONTENT_OFFSET ? pendingContentOffsetX : getScrollX();
+      int scrollToY =
+          pendingContentOffsetY != UNSET_CONTENT_OFFSET ? pendingContentOffsetY : getScrollY();
+      scrollTo(scrollToX, scrollToY);
+    }
+
     ReactScrollViewHelper.emitLayoutEvent(this);
   }
 

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -286,14 +286,17 @@ protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 
   @Override
   protected void onLayout(boolean changed, int l, int t, int r, int b) {
-    // Call with the present values in order to re-layout if necessary
-    // If a "pending" content offset value has been set, we restore that value.
-    // Upon call to scrollTo, the "pending" values will be re-set.
-    int scrollToX =
-        pendingContentOffsetX != UNSET_CONTENT_OFFSET ? pendingContentOffsetX : getScrollX();
-    int scrollToY =
-        pendingContentOffsetY != UNSET_CONTENT_OFFSET ? pendingContentOffsetY : getScrollY();
-    scrollTo(scrollToX, scrollToY);
+    // Apply pending contentOffset in case it was set before the view was laid out.
+    if (isContentReady()) {
+      // If a "pending" content offset value has been set, we restore that value.
+      // Upon call to scrollTo, the "pending" values will be re-set.
+      int scrollToX =
+          pendingContentOffsetX != UNSET_CONTENT_OFFSET ? pendingContentOffsetX : getScrollX();
+      int scrollToY =
+          pendingContentOffsetY != UNSET_CONTENT_OFFSET ? pendingContentOffsetY : getScrollY();
+      scrollTo(scrollToX, scrollToY);
+    }
+
     ReactScrollViewHelper.emitLayoutEvent(this);
   }