Cómo usar una base de datos existente con una aplicación de Android

Ya he creado una base de datos SQLite. Quiero usar este archivo de base de datos con mi proyecto de Android. Quiero agrupar esta base de datos con mi aplicación.

En lugar de crear una nueva base de datos, ¿cómo puede la aplicación obtener acceso a esta base de datos y usarla como su base de datos?

NOTA: antes de probar este código, encuentre esta línea en el siguiente código:

 private static String DB_NAME ="YourDbName"; // Database name 

DB_NAME aquí es el nombre de tu base de datos. Se supone que tiene una copia de la base de datos en la carpeta de activos, por ejemplo, si su nombre de base de datos es ordersDB, entonces el valor de DB_NAME será ordersDB,

 private static String DB_NAME ="ordersDB"; 

Mantenga la base de datos en la carpeta de activos y luego siga los pasos a continuación:

Clase DataHelper:

 import java.io.File; 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.SQLiteOpenHelper; import android.util.Log; public class DataBaseHelper extends SQLiteOpenHelper { private static String TAG = "DataBaseHelper"; // Tag just for the LogCat window //destination path (location) of our database on device private static String DB_PATH = ""; private static String DB_NAME ="YourDbName";// Database name private SQLiteDatabase mDataBase; private final Context mContext; public DataBaseHelper(Context context) { super(context, DB_NAME, null, 1);// 1? Its database Version if(android.os.Build.VERSION.SDK_INT >= 17){ DB_PATH = context.getApplicationInfo().dataDir + "/databases/"; } else { DB_PATH = "/data/data/" + context.getPackageName() + "/databases/"; } this.mContext = context; } public void createDataBase() throws IOException { //If the database does not exist, copy it from the assets. boolean mDataBaseExist = checkDataBase(); if(!mDataBaseExist) { this.getReadableDatabase(); this.close(); try { //Copy the database from assests copyDataBase(); Log.e(TAG, "createDatabase database created"); } catch (IOException mIOException) { throw new Error("ErrorCopyingDataBase"); } } } //Check that the database exists here: /data/data/your package/databases/Da Name private boolean checkDataBase() { File dbFile = new File(DB_PATH + DB_NAME); //Log.v("dbFile", dbFile + " "+ dbFile.exists()); return dbFile.exists(); } //Copy the database from assets private void copyDataBase() throws IOException { InputStream mInput = mContext.getAssets().open(DB_NAME); String outFileName = DB_PATH + DB_NAME; OutputStream mOutput = new FileOutputStream(outFileName); byte[] mBuffer = new byte[1024]; int mLength; while ((mLength = mInput.read(mBuffer))>0) { mOutput.write(mBuffer, 0, mLength); } mOutput.flush(); mOutput.close(); mInput.close(); } //Open the database, so we can query it public boolean openDataBase() throws SQLException { String mPath = DB_PATH + DB_NAME; //Log.v("mPath", mPath); mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY); //mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS); return mDataBase != null; } @Override public synchronized void close() { if(mDataBase != null) mDataBase.close(); super.close(); } } 

Escribe una clase DataAdapter como:

 import java.io.IOException; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.util.Log; public class TestAdapter { protected static final String TAG = "DataAdapter"; private final Context mContext; private SQLiteDatabase mDb; private DataBaseHelper mDbHelper; public TestAdapter(Context context) { this.mContext = context; mDbHelper = new DataBaseHelper(mContext); } public TestAdapter createDatabase() throws SQLException { try { mDbHelper.createDataBase(); } catch (IOException mIOException) { Log.e(TAG, mIOException.toString() + " UnableToCreateDatabase"); throw new Error("UnableToCreateDatabase"); } return this; } public TestAdapter open() throws SQLException { try { mDbHelper.openDataBase(); mDbHelper.close(); mDb = mDbHelper.getReadableDatabase(); } catch (SQLException mSQLException) { Log.e(TAG, "open >>"+ mSQLException.toString()); throw mSQLException; } return this; } public void close() { mDbHelper.close(); } public Cursor getTestData() { try { String sql ="SELECT * FROM myTable"; Cursor mCur = mDb.rawQuery(sql, null); if (mCur!=null) { mCur.moveToNext(); } return mCur; } catch (SQLException mSQLException) { Log.e(TAG, "getTestData >>"+ mSQLException.toString()); throw mSQLException; } } } 

Ahora puedes usarlo como:

 TestAdapter mDbHelper = new TestAdapter(urContext); mDbHelper.createDatabase(); mDbHelper.open(); Cursor testdata = mDbHelper.getTestData(); mDbHelper.close(); 

EDITAR: Gracias a JDx

Para Android 4.1 (Jelly Bean), cambie:

 DB_PATH = "/data/data/" + context.getPackageName() + "/databases/"; 

a:

 DB_PATH = context.getApplicationInfo().dataDir + "/databases/"; 

en la clase DataHelper, este código funcionará en los usuarios múltiples de JB 4.2.

Si tiene una base de datos preconstruida, cópiela en la carpeta de activos y cree una nueva clase como DataBaseHelper que implemente SQLiteOpenHelper, luego utilice el siguiente código:

 import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DataBaseHelperClass extends SQLiteOpenHelper{ //The Android's default system path of your application database. private static String DB_PATH = "/data/data/package_name/databases/"; // Data Base Name. private static final String DATABASE_NAME = "DBName.sqlite"; // Data Base Version. private static final int DATABASE_VERSION = 1; // Table Names of Data Base. static final String TABLE_Name = "tableName"; public Context context; static SQLiteDatabase sqliteDataBase; /** * Constructor * Takes and keeps a reference of the passed context in order to access to the application assets and resources. * @param context * Parameters of super() are 1. Context * 2. Data Base Name. * 3. Cursor Factory. * 4. Data Base Version. */ public DataBaseHelperClass(Context context) { super(context, DATABASE_NAME, null ,DATABASE_VERSION); this.context = context; } /** * Creates a empty database on the system and rewrites it with your own database. * 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. * */ public void createDataBase() throws IOException{ //check if the database exists boolean databaseExist = checkDataBase(); if(databaseExist){ // Do Nothing. }else{ this.getWritableDatabase(); copyDataBase(); }// end if else dbExist } // end createDataBase(). /** * 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 */ public boolean checkDataBase(){ File databaseFile = new File(DB_PATH + DATABASE_NAME); return databaseFile.exists(); } /** * 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 byte stream. * */ private void copyDataBase() throws IOException{ //Open your local db as the input stream InputStream myInput = context.getAssets().open(DATABASE_NAME); // Path to the just created empty db String outFileName = DB_PATH + DATABASE_NAME; //Open the empty db as the output stream OutputStream myOutput = new FileOutputStream(outFileName); //transfer bytes from the input file to the output file 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(); } /** * This method opens the data base connection. * First it create the path up till data base of the device. * Then create connection with data base. */ public void openDataBase() throws SQLException{ //Open the database String myPath = DB_PATH + DATABASE_NAME; sqliteDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE); } /** * This Method is used to close the data base connection. */ @Override public synchronized void close() { if(sqliteDataBase != null) sqliteDataBase.close(); super.close(); } /** * Apply your methods and class to fetch data using raw or queries on data base using * following demo example code as: */ public String getUserNameFromDB(){ String query = "select User_First_Name From "+TABLE_USER_DETAILS; Cursor cursor = sqliteDataBase.rawQuery(query, null); String userName = null; if(cursor.getCount()>0){ if(cursor.moveToFirst()){ do{ userName = cursor.getString(0); }while (cursor.moveToNext()); } } return userName; } @Override public void onCreate(SQLiteDatabase db) { // No need to write the create table query. // As we are using Pre built data base. // Which is ReadOnly. } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // No need to write the update table query. // As we are using Pre built data base. // Which is ReadOnly. // We should not update it as requirements of application. } } 

Espero que esto te ayudará…

Tuve problemas con los otros DatabaseHelpers con respecto a este problema, no estoy seguro de por qué.
Esto es lo que funcionó para mí:

 import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; public class DatabaseHelper extends SQLiteOpenHelper { private static final String TAG = DatabaseHelper.class.getSimpleName(); private final Context context; private final String assetPath; private final String dbPath; public DatabaseHelper(Context context, String dbName, String assetPath) throws IOException { super(context, dbName, null, 1); this.context = context; this.assetPath = assetPath; this.dbPath = "/data/data/" + context.getApplicationContext().getPackageName() + "/databases/" + dbName; checkExists(); } /** * Checks if the database asset needs to be copied and if so copies it to the * default location. * * @throws IOException */ private void checkExists() throws IOException { Log.i(TAG, "checkExists()"); File dbFile = new File(dbPath); if (!dbFile.exists()) { Log.i(TAG, "creating database.."); dbFile.getParentFile().mkdirs(); copyStream(context.getAssets().open(assetPath), new FileOutputStream( dbFile)); Log.i(TAG, assetPath + " has been copied to " + dbFile.getAbsolutePath()); } } private void copyStream(InputStream is, OutputStream os) throws IOException { byte buf[] = new byte[1024]; int c = 0; while (true) { c = is.read(buf); if (c == -1) break; os.write(buf, 0, c); } is.close(); os.close(); } @Override public void onCreate(SQLiteDatabase db) { } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } } 

Si ya tiene una base de datos, guárdela en su carpeta de activos y cópiela en su aplicación. Para obtener más detalles, consulte los principios básicos de la base de datos de Android .

Puedes hacer esto usando un proveedor de contenido . Cada elemento de datos utilizado en la aplicación permanece privado para la aplicación. Si una aplicación desea compartir datos entre aplicaciones, solo hay una técnica para lograrlo, utilizando un proveedor de contenido, que proporciona una interfaz para acceder a esos datos privados.