Add @empty support.

Bug: http://b.android.com/162428
Change-Id: Id7a981de2fce21213e12cdabcce4104f146fd4d3
diff --git a/tools/layoutlib/bridge/src/android/content/res/BridgeTypedArray.java b/tools/layoutlib/bridge/src/android/content/res/BridgeTypedArray.java
index 1803692..ae2c173 100644
--- a/tools/layoutlib/bridge/src/android/content/res/BridgeTypedArray.java
+++ b/tools/layoutlib/bridge/src/android/content/res/BridgeTypedArray.java
@@ -16,6 +16,7 @@
 
 package android.content.res;
 
+import com.android.annotations.Nullable;
 import com.android.ide.common.rendering.api.AttrResourceValue;
 import com.android.ide.common.rendering.api.LayoutLog;
 import com.android.ide.common.rendering.api.RenderResources;
@@ -40,9 +41,12 @@
 import android.view.ViewGroup.LayoutParams;
 
 import java.io.File;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Map;
 
+import static com.android.ide.common.rendering.api.RenderResources.*;
+
 /**
  * Custom implementation of TypedArray to handle non compiled resources.
  */
@@ -56,6 +60,11 @@
     private final String[] mNames;
     private final boolean[] mIsFramework;
 
+    // Contains ids that are @empty. We still store null in mResourceData for that index, since we
+    // want to save on the check against empty, each time a resource value is requested.
+    @Nullable
+    private int[] mEmptyIds;
+
     public BridgeTypedArray(BridgeResources resources, BridgeContext context, int len,
             boolean platformFile) {
         super(resources, null, null, 0);
@@ -90,19 +99,32 @@
         // fills TypedArray.mIndices which is used to implement getIndexCount/getIndexAt
         // first count the array size
         int count = 0;
+        ArrayList<Integer> emptyIds = null;
         for (int i = 0; i < mResourceData.length; i++) {
             ResourceValue data = mResourceData[i];
             if (data != null) {
-                if (RenderResources.REFERENCE_NULL.equals(data.getValue())) {
-                    // No need to store this resource value. This saves needless checking for
-                    // "@null" every time  an attribute is requested.
+                String dataValue = data.getValue();
+                if (REFERENCE_NULL.equals(dataValue) || REFERENCE_UNDEFINED.equals(dataValue)) {
                     mResourceData[i] = null;
+                } else if (REFERENCE_EMPTY.equals(dataValue)) {
+                    mResourceData[i] = null;
+                    if (emptyIds == null) {
+                        emptyIds = new ArrayList<Integer>(4);
+                    }
+                    emptyIds.add(i);
                 } else {
                     count++;
                 }
             }
         }
 
+        if (emptyIds != null) {
+            mEmptyIds = new int[emptyIds.size()];
+            for (int i = 0; i < emptyIds.size(); i++) {
+                mEmptyIds[i] = emptyIds.get(i);
+            }
+        }
+
         // allocate the table with an extra to store the size
         mIndices = new int[count+1];
         mIndices[0] = count;
@@ -748,6 +770,12 @@
         return index >= 0 && index < mResourceData.length && mResourceData[index] != null;
     }
 
+    @Override
+    public boolean hasValueOrEmpty(int index) {
+        return hasValue(index) || index >= 0 && index < mResourceData.length &&
+                mEmptyIds != null && Arrays.binarySearch(mEmptyIds, index) >= 0;
+    }
+
     /**
      * Retrieve the raw TypedValue for the attribute at <var>index</var>
      * and return a temporary object holding its data.  This object is only