Add gradient to navigation bar header

app/src/main/res/drawable/side_nav_bar.xml

@@ -2,8 +2,7 @@
     android:shape="rectangle">
     <gradient
         android:angle="135"
-        android:centerColor="#536dfe"
-        android:endColor="#536dfe"
-        android:startColor="#536dfe"
+        android:endColor="@color/colorPrimary"
+        android:startColor="@color/colorPrimaryDark"
         android:type="linear" />
 </shape>
\ No newline at end of file

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

@@ -17,7 +17,7 @@
         android:layout_width="64dp"
         android:layout_height="64dp"
         android:paddingTop="@dimen/nav_header_vertical_spacing"
-        android:src="@drawable/user_placeholder" />
+        app:srcCompat="@drawable/user_placeholder" />
 
     <TextView
         android:id="@+id/user_name_nav_header"