make sure JavaField is always white regardless of system theme setting

Author: Hisanobu Tomari

app/src/main/res/layout/activity_main.xml

@@ -6,7 +6,8 @@
     android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
-    tools:context=".MainActivity" >
+    tools:context=".MainActivity"
+                android:background="@color/javafield">
 
     <TextView
         android:id="@+id/textView1"

app/src/main/res/values/colors.xml

@@ -4,4 +4,5 @@
 	<color name="primary">#f00</color>
 	<color name="primary_dark">#a00</color>
 	<color name="accent">#f33</color>
+	<color name="javafield">#fff</color>
 </resources>