无法从资产复制SQLite数据库

Question

我尝试从资产目录复制SQLite数据库，以便以后访问。但是我做不到！

public class DatabaseAdapter {
    private static String DB_PATH = "/data/data/com.mypackage/databases/";
    private static String DB_NAME = "database.sqlite";
    private static String TABLE_NAME = "content_table";

    private SQLiteDatabase database = null;
    private final Context context;

    public DatabaseAdapter(Context context){
        this.context = context;
    }

    private void openDatabase() throws SQLiteException{
        DatabaseHelper databaseHelper = new DatabaseHelper(context, DB_NAME);
        SQLiteDatabase db = null;
        if(!checkDatabase()){
            try{
                //Tried to create db before copying, so file should exist
                db = databaseHelper.getReadableDatabase();
                db.close();

                copyDatabase();

            }catch(IOException exception){
                Log.d("DatabaseAdapter", "Error copying DB: "+exception);
            }
        }

        database = SQLiteDatabase.openDatabase(DB_PATH+DB_NAME, null, SQLiteDatabase.OPEN_READONLY);
    }

    private void closeDatabase(){
        database.close();
    }

    public ArrayList<String> queryCategories(){
        try{
            openDatabase();
        }catch(SQLiteException exc){
            exc.printStackTrace();
        }
        //.............................
        return result;
    }

    private boolean checkDatabase(){
        File dbFile = new File(DB_PATH + DB_NAME);
        return dbFile.exists();
    }

    private void copyDatabase() throws IOException{
        InputStream inputStream = context.getAssets().open(DB_NAME);

        String outFileName = DB_PATH + DB_NAME;

        OutputStream outputStream = new FileOutputStream(outFileName);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer))>0){
            outputStream.write(buffer, 0, length);
        }

        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }

}

DatabaseHelper很简单：

ublic class DatabaseHelper extends SQLiteOpenHelper {

    public DatabaseHelper(Context context, String name){
        super(context, name, null, 1);

    }


    @Override
    public void onCreate(SQLiteDatabase arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

尝试了一切！我尝试玩扩展！但是我仍然收到一个错误：复制数据库时出错：java.io.FileNotFoundException: /data/data/com.mypackage/databases/database.sqlite (No such file or directory)

我检查了模拟器，我的文件在那里，所以我应该可以写它！请任何帮助！真让我发疯！

UPD 我试图将其放在SD卡上，并且可以正常工作。但仍然无法理解为什么我无法将其写入应用程序数据文件夹。

Answer 1

我使用此助手，并且工作正常：

public class DBHelper extends SQLiteOpenHelper{

private final static String DB_PATH = "/data/data/[YOUR PACKAGE HERE]/databases/";

String dbName;
Context context;

File dbFile;

public DBHelper(Context context, String dbName, CursorFactory factory,
        int version) {
    super(context, dbName, factory, version);
    this.context = context;
    this.dbName = dbName;
    dbFile= new File(DB_PATH + dbName);
}

@Override
public synchronized SQLiteDatabase getWritableDatabase() {

    if(!dbFile.exists()){
        SQLiteDatabase db = super.getWritableDatabase();
        copyDataBase(db.getPath());
    }
    return super.getWritableDatabase();
}

@Override
public synchronized SQLiteDatabase getReadableDatabase() {
    if(!dbFile.exists()){
        SQLiteDatabase db = super.getReadableDatabase();
        copyDataBase(db.getPath());
    }
    return super.getReadableDatabase();
}

@Override
public void onCreate(SQLiteDatabase db) {}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}

private void copyDataBase(String dbPath){
    try{
        InputStream assestDB = context.getAssets().open("databases/"+dbName);

        OutputStream appDB = new FileOutputStream(dbPath,false);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = assestDB.read(buffer)) > 0) {
            appDB.write(buffer, 0, length);
        }

        appDB.flush();
        appDB.close();
        assestDB.close();
    }catch(IOException e){
        e.printStackTrace();
    }

}

}

考虑到数据库的文件扩展名是 .db ，并且我的数据库位于 资产/数据库/