DBHelper.java

package edu.purdue.app.dining;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.LinkedList;
import java.util.List;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DBHelper extends SQLiteOpenHelper {

	// Database version
	private static final int DB_VERSION = 1;
	
	// Database name
	private static final String DB_NAME = "db_meals";
	
	// Table names
	private static final String TABLE_MEALS = "t_meals";
	
	// Column names
	private static final String MEALS_ID = "_id";
	private static final String MEALS_DATE = "meals_date";
	private static final String MEALS_TIME = "meals_time";
	private static final String MEALS_LOC = "meals_loc";
	private static final String MEALS_REST = "meals_rest";
	private static final String MEALS_NAME = "meals_name";
	
	public DBHelper(Context context, String name, CursorFactory factory, int version) {
		super(context, DB_NAME, null, DB_VERSION);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		String create_table_meals = "" +
				"CREATE TABLE " + TABLE_MEALS + "( " +
				MEALS_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
				MEALS_DATE + " TEXT, " +
				MEALS_TIME + " TEXT, " + 
				MEALS_LOC + " TEXT, " + 
				MEALS_REST + " TEXT, " + 
				MEALS_NAME + " TEXT" + ");";
		db.execSQL(create_table_meals);
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// Destroy the old table and recreate it from scratch.
		// Import that data if we desire. Probably not necessary for this app.
	}
	
	/** Destroys the t_meals table from the database and recreates an empty one.
	 *  This is useful for both clearing out the database and when we need to add new columns. 
	 *  This will return true if it successfully destroyed and recreated the table. 
	 *  Otherwise, it will return false. */
	public void recreate() {
		SQLiteDatabase db = this.getWritableDatabase();
		Cursor c = db.rawQuery("select DISTINCT tbl_name from sqlite_master where tbl_name = '" + TABLE_MEALS +"'", null);
		
		if (c.getCount() > 0) {
			db.execSQL("DROP TABLE " + this.TABLE_MEALS);
			onCreate(db);
		} else {
			onCreate(db);
		}
		
	}
	
	/** Adds a meal to the database. Will return true if successful. */
	public boolean addMeal(Meal m) {
		SQLiteDatabase db = this.getWritableDatabase();
		ContentValues values = new ContentValues();
		
		values.put(MEALS_NAME, m.getTitle());
		values.put(MEALS_LOC, m.getLocationStr());
		values.put(MEALS_TIME, m.getTimeStr());
		values.put(MEALS_DATE, m.getDateStr());
		values.put(MEALS_REST, m.getRestaurant());
		
		long rowid = db.insert(TABLE_MEALS, null, values);
		if (rowid >= 0) {
			return true;
		} else {
			return false;
		}
	}
	
	/** Returns meals of a given day, time, and location. */
	public List<Meal> getMeals(GregorianCalendar day, Meal.Time time, Meal.Location loc) {
		SQLiteDatabase db = this.getReadableDatabase();
		
		Cursor query = db.query(TABLE_MEALS, 
				null, 
				MEALS_DATE + "=\'" + Meal.convertDate(day) + "\' and " + 
				MEALS_LOC + "=\'" + Meal.convertLoc(loc) + "\' and " + 
				MEALS_TIME + "=\'" + Meal.convertTime(time) + "\';", 
				null, null, null, null);
		
		List<Meal> meals = new LinkedList<Meal>();
		
		if (query.moveToFirst()) {
			do {
				String n_rest = query.getString(4);
				String n_title = query.getString(5);
				meals.add(new Meal(day, time, loc, n_rest, n_title));
			} while (query.moveToNext());
		}
		
		query.close();
		db.close();
		
		return meals;
	}

}