Refactor a few 100 lines of code out of the main Activity.

MyTracks/res/drawable/left_arrow_chart_stateful.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+Copyright 2010 Google Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+
+  <item android:state_window_focused="false"
+        android:drawable="@drawable/left_arrow_chart" />
+
+  <item android:state_pressed="true"
+        android:drawable="@drawable/left_arrow_chart_press" />
+
+  <item android:drawable="@drawable/left_arrow_chart" />
+
+</selector>