Alternative workaround for using private attribute

- SysUI studio has trouble referencing this private attribute
  directly, so move the resolving of the color to the code
  instead

Bug: 152086714
Test: Studio builds, numpad colors still reflect the
      colorSurface color when changing dark/light &
      wallpapers
Change-Id: I9a96c89010c41eaf6d14d5e1cfe86777cc30c8be

packages/SystemUI/res-keyguard/values/styles.xml

@@ -17,7 +17,7 @@
 */
 -->
 
-<resources xmlns:androidprv="http://schemas.android.com/apk/prv/res/android">
+<resources>
     <!-- Keyguard PIN pad styles -->
     <style name="Keyguard.TextView" parent="@android:style/Widget.DeviceDefault.TextView">
         <item name="android:textSize">@dimen/kg_status_line_font_size</item>
@@ -32,7 +32,9 @@
         <item name="android:stateListAnimator">@null</item>
     </style>
     <style name="NumPadKey" parent="Theme.SystemUI">
-      <item name="android:colorControlNormal">?androidprv:attr/colorSurface</item>
+      <!-- Studio can't directly reference ?androidprv:attr/colorSurface here, so this value
+           is resolved in {@link NumPadAnimator}. -->
+      <item name="android:colorControlNormal">@null</item>
       <item name="android:colorControlHighlight">?android:attr/colorAccent</item>
       <item name="android:background">@drawable/num_pad_key_background</item>
     </style>

packages/SystemUI/src/com/android/keyguard/NumPadAnimator.java

@@ -29,6 +29,7 @@ import androidx.annotation.StyleRes;
 
 import com.android.systemui.R;
 import com.android.systemui.animation.Interpolators;
+import com.android.systemui.util.Utils;
 
 /**
  * Provides background color and radius animations for key pad buttons.
@@ -100,7 +101,8 @@ class NumPadAnimator {
 
         ContextThemeWrapper ctw = new ContextThemeWrapper(context, mStyle);
         TypedArray a = ctw.obtainStyledAttributes(customAttrs);
-        mNormalColor = a.getColor(0, 0);
+        mNormalColor = Utils.getPrivateAttrColorIfUnset(ctw, a, 0, 0,
+                com.android.internal.R.attr.colorSurface);
         mHighlightColor = a.getColor(1, 0);
         a.recycle();
 

packages/SystemUI/src/com/android/systemui/util/Utils.java

@@ -21,8 +21,10 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.content.res.Resources;
+import android.content.res.TypedArray;
 import android.provider.Settings;
 import android.text.TextUtils;
+import android.view.ContextThemeWrapper;
 import android.view.View;
 
 import com.android.systemui.R;
@@ -177,4 +179,23 @@ public class Utils {
                 && resources.getBoolean(R.bool.config_use_split_notification_shade);
     }
 
+    /**
+     * Returns the color provided at the specified {@param attrIndex} in {@param a} if it exists,
+     * otherwise, returns the color from the private attribute {@param privAttrId}.
+     */
+    public static int getPrivateAttrColorIfUnset(ContextThemeWrapper ctw, TypedArray a,
+            int attrIndex, int defColor, int privAttrId) {
+        // If the index is specified, use that value
+        if (a.hasValue(attrIndex)) {
+            return a.getColor(attrIndex, defColor);
+        }
+
+        // Otherwise fallback to the value of the private attribute
+        int[] customAttrs = { privAttrId };
+        a = ctw.obtainStyledAttributes(customAttrs);
+        int color = a.getColor(0, defColor);
+        a.recycle();
+        return color;
+    }
+
 }