Make sure that AppBarLayout is laid out correctly

Currently, the scrolling view of a AppBarLayout relies
on CoLs pre draw listener to move itself. This is
problematic for things like activity transitions which
rely on correct position after a layout.

BUG: 23307267
Change-Id: Ibf508908cd22ef29d2c3752b299b8ce5d6346b0a

2 files changed, 24 insertions, 0 deletions

diff --git a/design/api/current.txt b/design/api/current.txt
index de4e09b1d9..ff682ee6f5 100644
--- a/design/api/current.txt
+++ b/design/api/current.txt
@@ -61,6 +61,7 @@ package android.support.design.widget {
     method public int getOverlayTop();
     method public boolean layoutDependsOn(android.support.design.widget.CoordinatorLayout, android.view.View, android.view.View);
     method public boolean onDependentViewChanged(android.support.design.widget.CoordinatorLayout, android.view.View, android.view.View);
+    method public boolean onLayoutChild(android.support.design.widget.CoordinatorLayout, android.view.View, int);
     method public boolean onMeasureChild(android.support.design.widget.CoordinatorLayout, android.view.View, int, int, int, int);
     method public void setOverlayTop(int);
   }
diff --git a/design/src/android/support/design/widget/AppBarLayout.java b/design/src/android/support/design/widget/AppBarLayout.java
index 78f8f9fb16..5cb8b733eb 100644
--- a/design/src/android/support/design/widget/AppBarLayout.java
+++ b/design/src/android/support/design/widget/AppBarLayout.java
@@ -1267,8 +1267,30 @@ public class AppBarLayout extends LinearLayout {
         }
 
         @Override
+        public boolean onLayoutChild(CoordinatorLayout parent, View child, int layoutDirection) {
+            // First lay out the child as normal
+            super.onLayoutChild(parent, child, layoutDirection);
+
+            // Now offset us correctly to be in the correct position. This is important for things
+            // like activity transitions which rely on accurate positioning after the first layout.
+            final List<View> dependencies = parent.getDependencies(child);
+            for (int i = 0, z = dependencies.size(); i < z; i++) {
+                if (updateOffset(parent, child, dependencies.get(i))) {
+                    // If we updated the offset, break out of the loop now
+                    break;
+                }
+            }
+            return true;
+        }
+
+        @Override
         public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
                 View dependency) {
+            updateOffset(parent, child, dependency);
+            return false;
+        }
+
+        private boolean updateOffset(CoordinatorLayout parent, View child, View dependency) {
             final CoordinatorLayout.Behavior behavior =
                     ((CoordinatorLayout.LayoutParams) dependency.getLayoutParams()).getBehavior();
             if (behavior instanceof Behavior) {
@@ -1276,6 +1298,7 @@ public class AppBarLayout extends LinearLayout {
                 final int offset = ((Behavior) behavior).getTopBottomOffsetForScrollingSibling();
                 setTopAndBottomOffset(dependency.getHeight() + offset
                         - getOverlapForOffset(dependency, offset));
+                return true;
             }
             return false;
         }