Persist.java :  » UnTagged » preflect » com » ryanm » preflect » Android Open Source

package com.ryanm.preflect;

import java.util.Arrays;
import java.util.Set;

import org.json.JSONObject;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.util.Log;

/**
 * Allows storage of configurations. Configurations are JSON-encoded
 * and placed in a {@link SharedPreferences}
 * 
 * @author ryanm
 */
public class Persist
{
  private Persist()
  {
  }

  private static SharedPreferences getPrefs( Activity act, String owner )
  {
    return act.getSharedPreferences( owner + ".config", Context.MODE_WORLD_WRITEABLE );
  }

  /**
   * Saves the configuration of an object tree
   * 
   * @param owner
   *           The activity that owns the data
   * @param savename
   *           The name of the saved data
   * @param roots
   *           The objects whose configuration to save
   */
  public static void save( Activity owner, String savename, Object... roots )
  {
    JSONObject json = Extract.extract( roots );
    save( owner, owner.getClass().getName(), savename, json );
  }

  /**
   * Loads and applies a saved configuration. If there's a problem in
   * loading or parsing the save it is deleted.
   * 
   * @param owner
   *           The activity that owns the data
   * @param savename
   *           The name of the saved data
   * @param roots
   *           The objects to apply the configuration to
   */
  public static void load( Activity owner, String savename, Object... roots )
  {
    JSONObject json = load( owner, owner.getClass().getName(), savename );

    if( json != null )
    {
      Apply.apply( json, roots );
    }
  }

  /**
   * Deletes a saved configuration
   * 
   * @param owner
   *           The activity that owns the data
   * @param savename
   *           The name of the save to delete
   */
  public static void delete( Activity owner, String savename )
  {
    deleteSave( owner, owner.getClass().getName(), savename );
  }

  /**
   * Lists saved configurations
   * 
   * @param owner
   *           The activity that owns the saves
   * @return A sorted list of save names
   */
  public static String[] listSaves( Activity owner )
  {
    return listSaves( owner, owner.getClass().getName() );
  }

  static void save( Activity act, String owner, String savename, JSONObject json )
  {
    SharedPreferences.Editor prefs = getPrefs( act, owner ).edit();
    prefs.putString( savename, json.toString() );
    prefs.commit();
  }

  static JSONObject load( Activity act, String owner, String savename )
  {
    SharedPreferences prefs = getPrefs( act, owner );
    String json = prefs.getString( savename, null );

    if( json != null )
    {
      try
      {
        return new JSONObject( json );
      }
      catch( Exception e )
      {
        Log.e( Preflect.LOG_TAG, "Problem parsing save \"" + savename
            + "\". I'll delete it", e );
        deleteSave( act, owner, savename );
        return null;
      }
    }
    else
    {
      Log.e( Preflect.LOG_TAG, "Requested save \"" + savename + "\" not found" );

      return null;
    }
  }

  static void deleteSave( Activity act, String owner, String savename )
  {
    SharedPreferences.Editor prefs = getPrefs( act, owner ).edit();
    prefs.remove( savename );
    prefs.commit();
  }

  static String[] listSaves( Activity act, String owner )
  {
    SharedPreferences prefs = getPrefs( act, owner );
    Set<String> saves = prefs.getAll().keySet();
    String[] array = saves.toArray( new String[ saves.size() ] );
    Arrays.sort( array );

    return array;
  }
}