Don't backup ringtone on non-telephony devices.

Restoring a device that supports telephony using the backup set of
a non-telephony device would cause the ringtone to be set to "None"
instead of the default value. This was due to the fact that on
non-telephony devices, the ringtone value was being backed up as
"_silent" instead of null.

Bug: 18777629

Change-Id: Idece1f874438a895169dbba7df1d716adea6660e

packages/SettingsProvider/src/com/android/providers/settings/SettingsHelper.java

@@ -30,6 +30,7 @@ import android.os.RemoteException;
 import android.os.ServiceManager;
 import android.os.UserManager;
 import android.provider.Settings;
+import android.telephony.TelephonyManager;
 import android.text.TextUtils;
 
 import java.util.Locale;
@@ -38,11 +39,14 @@ public class SettingsHelper {
     private static final String SILENT_RINGTONE = "_silent";
     private Context mContext;
     private AudioManager mAudioManager;
+    private TelephonyManager mTelephonyManager;
 
     public SettingsHelper(Context context) {
         mContext = context;
         mAudioManager = (AudioManager) context
                 .getSystemService(Context.AUDIO_SERVICE);
+        mTelephonyManager = (TelephonyManager) context
+                .getSystemService(Context.TELEPHONY_SERVICE);
     }
 
     /**
@@ -75,12 +79,23 @@ public class SettingsHelper {
     }
 
     public String onBackupValue(String name, String value) {
-        // Special processing for backing up ringtones
+        // Special processing for backing up ringtones & notification sounds
         if (Settings.System.RINGTONE.equals(name)
                 || Settings.System.NOTIFICATION_SOUND.equals(name)) {
             if (value == null) {
-                // Silent ringtone
-                return SILENT_RINGTONE;
+                if (Settings.System.RINGTONE.equals(name)) {
+                    // For ringtones, we need to distinguish between non-telephony vs telephony
+                    if (mTelephonyManager != null && mTelephonyManager.isVoiceCapable()) {
+                        // Backup a null ringtone as silent on voice-capable devices
+                        return SILENT_RINGTONE;
+                    } else {
+                        // Skip backup of ringtone on non-telephony devices.
+                        return null;
+                    }
+                } else {
+                    // Backup a null notification sound as silent
+                    return SILENT_RINGTONE;
+                }
             } else {
                 return getCanonicalRingtoneValue(value);
             }