SQLiteOpenHelper - creating database on SD card

问题

in my test android app I intend to create and access database file, which will be located on SD card. I am using main activity with help of a class, which extends SQLiteOpenHelper. I want to use it the same way as before, but I have to somehow change the database PATH. Do you know, how to achieve it?

thx

My current code of a class which extends SQLiteOpenHelper:

public class DatabaseDefinition extends SQLiteOpenHelper{
private static final String DATABASE_NAME="test.db";
private static final int DATABASE_VERSION=1;

public DatabaseDefinition(Context context) {
    super(context,DATABASE_NAME,null, DATABASE_VERSION);

}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE "+TABLE_NAME+" ("+ _ID +" INTEGER PRIMARY KEY AUTOINCREMENT, "+ NAME+" TEXT NOT NULL, " +SURNAME+" TEXT NOT NULL, "+PHONE+" INT NOT NULL);");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS" + TABLE_NAME);
    onCreate(db);

}

And code of my main:

public class DatabaseExampleActivity extends Activity {
   private DatabaseDefinition database;
   private static String[] FROM={_ID, NAME, SURNAME,PHONE};
   private static String ORDER_BY=" DESC";


   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       database= new DatabaseDefinition(this); 
       try{
         String name = null;
         String surname=null;
         int phone=0;
         addEvent("John", "Black", 111012345);

    }finally{
        database.close();
    }
  }



}

回答1:

First you have to specify the path of the sdcard. You can do that by creating a string like this:

public static final String  DATABASE_FILE_PATH = "/sdcard";

But for you should call

Environment.getExternalStorageDirectory()

to get the root path to the SD card and use that to create the database. After that you create the database as you want. Here is an example

public class DatabaseHelper
{ 
   private static final String TAG                  = "DatabaseHelper";

  public static final String  DATABASE_FILE_PATH      = Environment.getExternalStorageDirectory();
  public static final String  DATABASE_NAME      = "mydb"; 
  public static final String  TRACKS_TABLE        = "tracks";
  public static final String  TRACK_INFO_TABLE        = "track_info";

  private static final String TRACKS_TABLE_CREATE     = "create table "
           + TRACKS_TABLE
           + " (_id integer primary key autoincrement, title text not null, description text null, created_at date not null);";

  private static final String TRACK_INFO_TABLE_CREATE = "create table " 
           + TRACK_INFO_TABLE 
           + " (_id integer primary key autoincrement, track_id integer not null, latitude real not null, longitude real not null, altitude real not null, created_at date not null);";

private SQLiteDatabase      database;

public DatabaseHelper() 
{  
    try
    {
        database = SQLiteDatabase.openDatabase(DATABASE_FILE_PATH
            + File.separator + DATABASE_NAME, null,SQLiteDatabase.OPEN_READWRITE);
    }
    catch (SQLiteException ex)
    {
        Log.e(TAG, "error -- " + ex.getMessage(), ex);
        // error means tables does not exits
        createTables();
    }
    finally
    {
        DBUtil.safeCloseDataBase(database);
    }
}

private void createTables()
{
    database.execSQL(TRACKS_TABLE_CREATE);
    database.execSQL(TRACK_INFO_TABLE_CREATE);
}

public void close()
{
    DBUtil.safeCloseDataBase(database);
}

public SQLiteDatabase getReadableDatabase()
{
    database = SQLiteDatabase.openDatabase(DATABASE_FILE_PATH
            + File.separator + DATABASE_NAME, null,
            SQLiteDatabase.OPEN_READONLY);
    return database;
}

public SQLiteDatabase getWritableDatabase()
{
    database = SQLiteDatabase.openDatabase(DATABASE_FILE_PATH
            + File.separator + DATABASE_NAME, null,
            SQLiteDatabase.OPEN_READWRITE);
    return database;
}

And in the end you have to set permission in manifest like this: android.permission.WRITE_EXTERNAL_STORAGE

Good luck :) Arkde

回答2:

If some of you want to create sqlite database on sd card but you still want to keep using class which extends sqliteOpenHelper, you can visit this answer.

You just have to add another class, implement it on your class (which extends sqliteOpenHelper) in super(), then change the path on your new class.

Note: If you are using HC or ICS you need to describe the "external_sd" on your path. Because HC and ICS will still report storage that's physically built into the device

来源：https://stackoverflow.com/questions/7229450/sqliteopenhelper-creating-database-on-sd-card

标签

android

database

sqlite

sd-card

sqliteopenhelper