CODEWITHSUNDEEP
androidsqlite
NullPointerException
NullPointerException

Reputation: 37577

Problems reading and opening a Sqlite database from a file

I have an app that must open a sqlitedatabase from a .db file on assets folder. This database must be opened each time the app starts.

I'm checking some tutorials for deal with sqlite databases in android and for load sqlite databases from a file. I merge all these tutorials in this code, but it doesn't works.

My database contains a TABLE called items wich haves some data inside, but when i call a SELECT * sentence from items i got an exception telling me that items table doesn't exists:

        String databaseName="frases";

    SQLiteManager sqlManager = new SQLiteManager(this); 
    sqlManager.open(databaseName);

    List<String> nombres = new ArrayList<String>();
    Cursor cursor=sqlManager.rawQuery("SELECT * FROM 'items'");
    while (cursor.moveToNext()) {
        nombres.add(cursor.getString(1));
    }

    for (int i=0; i<nombres.size();i++){
        Log.d("DATABASE", "Nombre: "+nombres.get(i));
    }

    sqlManager.close(); //Cerramos la base de datos

And this is my SQLiteManager class:

public class SQLiteManager {
private DemoSQLiteHelper dbHelper;
private SQLiteDatabase db;
private static Context ctx;

public SQLiteManager(Context ctx) {
    this.ctx = ctx;
}

public void open(String databaseName) throws SQLException {
    dbHelper = new DemoSQLiteHelper(ctx, databaseName, null, 1);
    generateSQLiteDB(databaseName);
    db = dbHelper.getWritableDatabase();
}

public void close() {
    dbHelper.close();
}

public void execSQL(String sql){
    db.execSQL(sql);
}

public Cursor rawQuery(String sql){
    Cursor cursor=db.rawQuery(sql, null);
    return cursor;
}

public void clearDB() {
    dbHelper.clearDb(db);
}

public class DemoSQLiteHelper extends SQLiteOpenHelper {

    public DemoSQLiteHelper(Context contexto, String nombre, CursorFactory factory, int version) {
        super(contexto, nombre, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int versionAnterior, int versionNueva) {
    }

    public void clearDb(SQLiteDatabase db){
        onCreate(db);
    }               
}       

private void generateSQLiteDB(String databaseName) {        // 
    SQLiteDatabase db =  dbHelper.getReadableDatabase(); // by calling this line an empty database will be created into the default system path of this app - we will then overwrite this with the database from the server
    db.close();
    OutputStream os = null;
    InputStream is = null;
    try{
        is =  ctx.getAssets().open(databaseName+".db");
        os = new FileOutputStream("/data/data/com.DemoSqlite/databases/"+databaseName+".db");   
        copyFile(os, is);
    }catch (Exception e) {
        Log.e("DB", "Database not found", e);                          
    }finally{
        try{
            if(os != null)
                os.close();     
            if(is != null)
                is.close();
        } catch (IOException e) {Log.e("DB", "Can't close adapters");}
    }
}

private void copyFile(OutputStream os, InputStream is) throws IOException {
    byte[] buffer = new byte[1024];
    int length;
    while((length = is.read(buffer))>0)
        os.write(buffer, 0, length);        
    os.flush();
}   
}

What is wrong in my code?

Thanks

Upvotes: 0

Views: 1055

Answers (1)

biegleux
biegleux

Reputation: 13247

Replace

dbHelper = new DemoSQLiteHelper(ctx, databaseName, null, 1);

with

dbHelper = new DemoSQLiteHelper(ctx, databaseName + ".db", null, 1);

in your SQLiteManager.open() method.

Although you copy database from assets, you pass frases database name to your SQLiteHelper, not frases.db so your helper uses wrong database file.

You are copying your database from assets everytime you instantiate your SQL manager. That's wrong approach. Take a look at this example how to move your database from assets https://stackoverflow.com/a/11601770/1300995.

Upvotes: 1

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