Fixed a RTL layouting bug with LinearLayout

When the RTL properties of a horizontal LinearLayout
changed, nobody enforced the view to be layouted anew,
even though its layout is dependent on the layout
direction. This could lead to stale layouts being
temporarily layouted the wrong way.

Bug: 20495301
Change-Id: I979c8d86ee711626b2901b65ebdf007c1eb1c0fa

3 files changed, 25 insertions, 0 deletions

diff --git a/core/java/android/util/LayoutDirection.java b/core/java/android/util/LayoutDirection.java
index 20af20b..03077e4 100644
--- a/core/java/android/util/LayoutDirection.java
+++ b/core/java/android/util/LayoutDirection.java
@@ -27,6 +27,12 @@ public final class LayoutDirection {
     private LayoutDirection() {}
 
     /**
+     * An undefined layout direction.
+     * @hide
+     */
+    public static final int UNDEFINED = -1;
+
+    /**
      * Horizontal layout direction is from Left to Right.
      */
     public static final int LTR = 0;
diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 342315b..5dd5ab8 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -1872,6 +1872,12 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
     public @interface ResolvedLayoutDir {}
 
     /**
+     * A flag to indicate that the layout direction of this view has not been defined yet.
+     * @hide
+     */
+    public static final int LAYOUT_DIRECTION_UNDEFINED = LayoutDirection.UNDEFINED;
+
+    /**
      * Horizontal layout direction of this view is from Left to Right.
      * Use with {@link #setLayoutDirection}.
      */
diff --git a/core/java/android/widget/LinearLayout.java b/core/java/android/widget/LinearLayout.java
index f153ce5..9d14254 100644
--- a/core/java/android/widget/LinearLayout.java
+++ b/core/java/android/widget/LinearLayout.java
@@ -185,6 +185,8 @@ public class LinearLayout extends ViewGroup {
     private int mShowDividers;
     private int mDividerPadding;
 
+    private int mLayoutDirection = View.LAYOUT_DIRECTION_UNDEFINED;
+
     public LinearLayout(Context context) {
         this(context, null);
     }
@@ -1567,6 +1569,17 @@ public class LinearLayout extends ViewGroup {
         }
     }
 
+    @Override
+    public void onRtlPropertiesChanged(@ResolvedLayoutDir int layoutDirection) {
+        super.onRtlPropertiesChanged(layoutDirection);
+        if (layoutDirection != mLayoutDirection) {
+            mLayoutDirection = layoutDirection;
+            if (mOrientation == HORIZONTAL) {
+                requestLayout();
+            }
+        }
+    }
+
     /**
      * Position the children during a layout pass if the orientation of this
      * LinearLayout is set to {@link #HORIZONTAL}.