android - 如何从在sqllite中创建和导出的 Assets 文件夹android中放置数据库和读取数据库

Question

我是 Android 开发新手。我正在通过 SQLite Manager 0.8.1 创建一个数据库。用户表包含两个字段，用户名和密码。我创建了数据库文件并将其放在 assets 文件夹中。现在我正在尝试从 Assets 文件夹中读取数据库。最好的方法是什么？任何帮助将不胜感激。

Answer 1

public class DataBaseHelper extends SQLiteOpenHelper {
    private SQLiteDatabase myDataBase;
    private final Context myContext;
    private static final String DATABASE_NAME = "YOURDBNAME";
    public final static String DATABASE_PATH = "/data/data/com.your.packagename/databases/";
    public static final int DATABASE_VERSION = 1;
    public DataBaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.myContext = context;

    }




    //Create a empty database on the system
    public void createDatabase() throws IOException
    {

          boolean dbExist = checkDataBase();

          if(dbExist)
          {
                Log.v("DB Exists", "db exists");
                // By calling this method here onUpgrade will be called on a
                // writeable database, but only if the version number has been
                // bumped
                //onUpgrade(myDataBase, DATABASE_VERSION_old, DATABASE_VERSION);
          }

          boolean dbExist1 = checkDataBase();
          if(!dbExist1)
          {
                this.getReadableDatabase();
                try
                {
                      this.close();    
                      copyDataBase();
                }
                catch (IOException e)
                {
                      throw new Error("Error copying database");
                }
          }

    }
    //Check database already exist or not
    private boolean checkDataBase()
    {
          boolean checkDB = false;
          try
          {
                String myPath = DATABASE_PATH + DATABASE_NAME;
                File dbfile = new File(myPath);
                checkDB = dbfile.exists();
          }
          catch(SQLiteException e)
          {
          }
          return checkDB;
    }
    //Copies your database from your local assets-folder to the just created empty database in the system folder
    private void copyDataBase() throws IOException
    {

        InputStream mInput = myContext.getAssets().open(DATABASE_NAME);
        String outFileName = DATABASE_PATH + DATABASE_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[2024];
        int mLength;
        while ((mLength = mInput.read(mBuffer)) > 0) {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }
  //delete database
    public void db_delete()
    {
          File file = new File(DATABASE_PATH + DATABASE_NAME);
          if(file.exists())
          {
                file.delete();
                System.out.println("delete database file.");
          }
    }
  //Open database
    public void openDatabase() throws SQLException
    {
          String myPath = DATABASE_PATH + DATABASE_NAME;
          myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
    }

    public synchronized void closeDataBase()throws SQLException
    {
          if(myDataBase != null)
                myDataBase.close();
          super.close();
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
         if (newVersion > oldVersion)
         {
               Log.v("Database Upgrade", "Database version higher than old.");
               db_delete();
         }

    }

}

并实现它

DataBaseHelper dbhelper = new DataBaseHelper(getApplicationContext());

        db = dbhelper.getWritableDatabase();

为此:

Cursor cur;
    cur_Herbs = db.rawQuery("select * from TABLENAME where  name like '"
            + edit_text_name.gettext.tostring() + "'", null);

        if (cur.moveToFirst()) {
            do {
                int name = cur.getColumnIndex("name");
                int pwd= cur.getColumnIndex("pwd");
str_name = cur.getString(name).toString();
                str_pwd= cur.getString(ped).toString();
if(str_name.equals(edittext_uname.gettext.tostring()and str_pwd.equals(edittext_pwd.gettext.tostring()))
{

//code for if loginn
}
} while (cur_Herbs.moveToNext());


}