altoslib: Make AltosPreferencesBackend abstract. Add set/put Serializable

This lets us add functionality to this directly, such as the new
serializable APIs.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroidPreferencesBackend.java b/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroidPreferencesBackend.java
index c2db3774..5c7ec513 100644
--- a/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroidPreferencesBackend.java
+++ b/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroidPreferencesBackend.java
@@ -26,7 +26,7 @@ import android.util.*;
 
 import org.altusmetrum.altoslib_10.*;
 
-public class AltosDroidPreferencesBackend implements AltosPreferencesBackend {
+public class AltosDroidPreferencesBackend extends AltosPreferencesBackend {
 	public final static String        NAME    = "org.altusmetrum.AltosDroid";
 	private Context                   context = null;
 	private SharedPreferences         prefs   = null;