Android: Copy/Duplicate SharedPreferences

Question

Is there a way to copy or duplicate a SharedPreference? Or will I need to get each variable from one and then put them in another?

Answer 1

Try Something Like this:

//sp1 is the shared pref to copy to
SharedPreferences.Editor ed = sp1.edit(); 
SharedPreferences sp = Sp2; //The shared preferences to copy from
ed.clear(); // This clears the one we are copying to, but you don't necessarily need to do that.
//Cycle through all the entries in the sp
for(Entry<String,?> entry : sp.getAll().entrySet()){ 
 Object v = entry.getValue(); 
 String key = entry.getKey();
 //Now we just figure out what type it is, so we can copy it.
 // Note that i am using Boolean and Integer instead of boolean and int.
 // That's because the Entry class can only hold objects and int and boolean are primatives.
 if(v instanceof Boolean) 
 // Also note that i have to cast the object to a Boolean 
 // and then use .booleanValue to get the boolean
    ed.putBoolean(key, ((Boolean)v).booleanValue());
 else if(v instanceof Float)
    ed.putFloat(key, ((Float)v).floatValue());
 else if(v instanceof Integer)
    ed.putInt(key, ((Integer)v).intValue());
 else if(v instanceof Long)
    ed.putLong(key, ((Long)v).longValue());
 else if(v instanceof String)
    ed.putString(key, ((String)v));         
}
ed.commit(); //save it.

Hope this helps.

Answer 2

The Kotlin version:

fun SharedPreferences.copyTo(dest: SharedPreferences) = with(dest.edit()) {
  for (entry in all.entries) {
    val value = entry.value ?: continue
    val key = entry.key
    when (value) {
      is String -> putString(key, value)
      is Set<*> -> putStringSet(key, value as Set<String>)
      is Int -> putInt(key, value)
      is Long -> putLong(key, value)
      is Float -> putFloat(key, value)
      is Boolean -> putBoolean(key, value)
      else -> error("Unknown value type: $value")
    }
  }
  apply()
}

Usage:

val prefs1 = getSharedPreferences("test1", MODE_PRIVATE)
val prefs2 = getSharedPreferences("test2", MODE_PRIVATE)

prefs1.copyTo(prefs2)

Answer 3

Here a version that also supports string sets.

public static void copySharedPreferences(SharedPreferences fromPreferences, SharedPreferences toPreferences) {
    copySharedPreferences(fromPreferences, toPreferences, true);
}

public static void copySharedPreferences(SharedPreferences fromPreferences, SharedPreferences toPreferences, boolean clear) {

    SharedPreferences.Editor editor = toPreferences.edit();
    if (clear) {
        editor.clear();
    }
    copySharedPreferences(fromPreferences, editor);
    editor.commit();
}

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@SuppressWarnings({"unchecked", "ConstantConditions"})
public static void copySharedPreferences(SharedPreferences fromPreferences, SharedPreferences.Editor toEditor) {

    for (Map.Entry<String, ?> entry : fromPreferences.getAll().entrySet()) {
        Object value = entry.getValue();
        String key = entry.getKey();
        if (value instanceof String) {
            toEditor.putString(key, ((String) value));
        } else if (value instanceof Set) {
            toEditor.putStringSet(key, (Set<String>) value); // EditorImpl.putStringSet already creates a copy of the set
        } else if (value instanceof Integer) {
            toEditor.putInt(key, (Integer) value);
        } else if (value instanceof Long) {
            toEditor.putLong(key, (Long) value);
        } else if (value instanceof Float) {
            toEditor.putFloat(key, (Float) value);
        } else if (value instanceof Boolean) {
            toEditor.putBoolean(key, (Boolean) value);
        }
    }
}