fix mContentOffsetY sometimes inaccurate

weex/android/bindingx_weex_plugin/src/main/java/com/alibaba/android/bindingx/plugin/weex/BindingXScrollHandler.java

@@ -328,7 +328,11 @@ public void onScrolled(RecyclerView recyclerView, final int dx, final int dy) {
             // so you should bind it as early as possible
 
             if(ViewCompat.isInLayout(recyclerView) && mComponentRef != null && mComponentRef.get() != null) {
-                mContentOffsetY = Math.abs(mComponentRef.get().calcContentOffset(recyclerView));
+                if (RecycleUtil.recyclerVerticalScrollOffset(recyclerView) != 0){
+                    mContentOffsetY = Math.abs(mComponentRef.get().calcContentOffset(recyclerView));
+                } else {
+                    mContentOffsetY = 0;
+                }
             } else {
                 mContentOffsetY += dy;
             }

weex/android/bindingx_weex_plugin/src/main/java/com/alibaba/android/bindingx/plugin/weex/RecycleUtil.java

@@ -0,0 +1,26 @@
+package com.alibaba.android.bindingx.plugin.weex;
+
+import android.support.annotation.NonNull;
+import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.StaggeredGridLayoutManager;
+import android.view.View;
+
+public class RecycleUtil {
+    public static int recyclerVerticalScrollOffset(@NonNull RecyclerView recyclerView) {
+        if (recyclerView.getLayoutManager() instanceof LinearLayoutManager) {
+            LinearLayoutManager manager = (LinearLayoutManager) recyclerView.getLayoutManager();
+            int position = manager.findFirstVisibleItemPosition();
+            View firstItemView = manager.findViewByPosition(position);
+            return firstItemView.getTop();
+        } else if (recyclerView.getLayoutManager() instanceof StaggeredGridLayoutManager) {
+            StaggeredGridLayoutManager manager = (StaggeredGridLayoutManager) recyclerView.getLayoutManager();
+            int[] firstVisibleItems = manager.findFirstVisibleItemPositions(null);
+            if (firstVisibleItems.length > 0) {
+                View firstItemView = manager.findViewByPosition(firstVisibleItems[0]);
+                return firstItemView.getTop();
+            }
+        }
+        return recyclerView.computeVerticalScrollOffset();
+    }
+}