Initialize preferences with default values.

src/main/AndroidManifest.xml

@@ -70,6 +70,7 @@ limitations under the License.
         android:smallScreens="true"
         android:xlargeScreens="true" />
     <application
+        android:name=".InitPreferences"
         android:allowBackup="true"
         android:hardwareAccelerated="true"
         android:icon="@drawable/ic_logo"

src/main/java/de/dennisguse/opentracks/InitPreferences.java

@@ -0,0 +1,19 @@
+package de.dennisguse.opentracks;
+
+import android.app.Application;
+import android.preference.PreferenceManager;
+
+public class InitPreferences extends Application {
+    @Override
+    public void onCreate() {
+        super.onCreate();
+
+        //Set default values of preferences on first start.
+        PreferenceManager.setDefaultValues(this, R.xml.settings, false);
+        PreferenceManager.setDefaultValues(this, R.xml.settings_advanced, false);
+        PreferenceManager.setDefaultValues(this, R.xml.settings_chart, false);
+        PreferenceManager.setDefaultValues(this, R.xml.settings_recording, false);
+        PreferenceManager.setDefaultValues(this, R.xml.settings_sensors, false);
+        PreferenceManager.setDefaultValues(this, R.xml.settings_statistics, false);
+    }
+}