Distinguish unspecified and explicit null values in resources

BUG: 17919345
Change-Id: Ic4f04f7dd0f986f58a749b5950d80c1cfdb074ea

2 files changed, 35 insertions, 0 deletions

diff --git a/core/java/android/content/res/TypedArray.java b/core/java/android/content/res/TypedArray.java
index 73b93c6..02602fb 100644
--- a/core/java/android/content/res/TypedArray.java
+++ b/core/java/android/content/res/TypedArray.java
@@ -807,6 +807,9 @@ public class TypedArray {
 
     /**
      * Determines whether there is an attribute at <var>index</var>.
+     * <p>
+     * <strong>Note:</strong> If the attribute was set to {@code @empty} or
+     * {@code @undefined}, this method returns {@code false}.
      *
      * @param index Index of attribute to retrieve.
      *
@@ -824,6 +827,27 @@ public class TypedArray {
     }
 
     /**
+     * Determines whether there is an attribute at <var>index</var>, returning
+     * {@code true} if the attribute was explicitly set to {@code @empty} and
+     * {@code false} only if the attribute was undefined.
+     *
+     * @param index Index of attribute to retrieve.
+     *
+     * @return True if the attribute has a value or is empty, false otherwise.
+     */
+    public boolean hasValueOrEmpty(int index) {
+        if (mRecycled) {
+            throw new RuntimeException("Cannot make calls to a recycled instance!");
+        }
+
+        index *= AssetManager.STYLE_NUM_ENTRIES;
+        final int[] data = mData;
+        final int type = data[index+AssetManager.STYLE_TYPE];
+        return type != TypedValue.TYPE_NULL
+                || data[index+AssetManager.STYLE_DATA] == TypedValue.DATA_NULL_EMPTY;
+    }
+
+    /**
      * Retrieve the raw TypedValue for the attribute at <var>index</var>
      * and return a temporary object holding its data.  This object is only
      * valid until the next call on to {@link TypedArray}.
diff --git a/core/java/android/util/TypedValue.java b/core/java/android/util/TypedValue.java
index 931fb81..d42ed03 100644
--- a/core/java/android/util/TypedValue.java
+++ b/core/java/android/util/TypedValue.java
@@ -139,6 +139,17 @@ public class TypedValue {
     /* ------------------------------------------------------------ */
 
     /**
+     * {@link #TYPE_NULL} data indicating the value was not specified.
+     */
+    public static final int DATA_NULL_UNDEFINED = 0;
+    /**
+     * {@link #TYPE_NULL} data indicating the value was explicitly set to null.
+     */
+    public static final int DATA_NULL_EMPTY = 1;
+
+    /* ------------------------------------------------------------ */
+
+    /**
      * If {@link #density} is equal to this value, then the density should be
      * treated as the system's default density value: {@link DisplayMetrics#DENSITY_DEFAULT}.
      */