Added database file and handler

SWADroid/src/es/ugr/swad/swadroid/model/DataBaseHelper.java

@@ -0,0 +1,116 @@
+package es.ugr.swad.swadroid.model;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import android.content.Context;
+import android.database.SQLException;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteException;
+import android.database.sqlite.SQLiteOpenHelper;
+
+public class DataBaseHelper extends SQLiteOpenHelper{
+	//The Android's default system path of your application database.
+	private static String DB_PATH = "/data/data/es.ugr.swad.swadroid/databases/";
+	private static String DB_NAME = "swadroid";
+	private SQLiteDatabase swadroidDataBase;
+	private final Context context;
+	
+	/**
+	 * Constructor
+	 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
+	 * @param context
+	 */
+	public DataBaseHelper(Context context) {
+		super(context, DB_NAME, null, 1);
+		this.context = context;
+	}
+	
+	/**
+	 * Creates a empty database on the system and rewrites it with your own database.
+	 * */
+	public void createDataBase() throws IOException{
+		boolean dbExist = checkDataBase();
+		if(dbExist){
+			//do nothing - database already exist
+		}else{
+			//By calling this method and empty database will be created into the default system path
+			//of your application so we are gonna be able to overwrite that database with our database.
+			this.getReadableDatabase();
+			try {
+				copyDataBase();
+			} catch (IOException e) {
+				throw new Error("Error copying database");
+			}
+		}
+	}
+	
+	/**
+	 * Check if the database already exist to avoid re-copying the file each time you open the application.
+	 * @return true if it exists, false if it doesn't
+	 */
+	private boolean checkDataBase(){
+		SQLiteDatabase checkDB = null;
+		try{
+			String myPath = DB_PATH + DB_NAME;
+			checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
+		}catch(SQLiteException e){
+			//database does't exist yet.
+		}
+
+		if(checkDB != null){
+			checkDB.close();
+		}
+		return checkDB != null ? true : false;
+	}
+	
+	/**
+	 * Copies your database from your local assets-folder to the just created empty database in the
+	 * system folder, from where it can be accessed and handled.
+	 * This is done by transferring bytestream.
+	 * */
+	private void copyDataBase() throws IOException{
+		//Open your local db as the input stream
+		InputStream myInput = context.getAssets().open(DB_NAME);
+		// Path to the just created empty db
+		String outFileName = DB_PATH + DB_NAME;
+		//Open the empty db as the output stream
+		OutputStream myOutput = new FileOutputStream(outFileName);
+		//transfer bytes from the inputfile to the outputfile
+		byte[] buffer = new byte[1024];
+		int length;
+		while ((length = myInput.read(buffer))>0){
+			myOutput.write(buffer, 0, length);
+		}
+		//Close the streams
+		myOutput.flush();
+		myOutput.close();
+		myInput.close();
+	}
+	
+	public void openDataBase() throws SQLException{
+		//Open the database
+		String myPath = DB_PATH + DB_NAME;
+		swadroidDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
+	}
+	
+	@Override
+	public synchronized void close() {
+		if(swadroidDataBase != null)
+			swadroidDataBase.close();
+		super.close();
+	}
+	
+	@Override
+	public void onCreate(SQLiteDatabase db) {
+	}
+	
+	@Override
+	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+	}
+	// Add your public helper methods to access and get content from the database.
+	// You could return cursors by doing "return swadroidDataBase.query(....)" so it'd be easy
+	// to you to create adapters for your views.
+}