Question

Stackoverflow社区的一个大问题，

我目前正在使用Android Studio中的登录表单并尝试连接到外部Sqlite数据库，但是我遇到的问题是复制的数据库中似乎没有表。对于表User上的select，导致以下错误：

*E/SQLiteLog: (1) no such table: User*

即使我的数据库已被复制并被打开：

Database is open

有人可以告诉我我做错了什么吗？我在Databasehelper类中添加了我正在使用的代码：

public class DatabaseHelper extends SQLiteOpenHelper {

    private Context mycontext;
    Connection sqliteConnection;
    // Database Version
    private static final int DATABASE_VERSION = 1;

    //Database Path
    private static String DB_PATH ="/data/data/"+ BuildConfig.APPLICATION_ID+"/databases/";


    // Database Name
    private static final String DATABASE_NAME = "mystockdb.db";

    // User table name
    private static final String TABLE_USER = "User";

    // User Table Columns names
    private static final String COLUMN_USER_ID = "user_id";
    private static final String COLUMN_USER_NAME = "name";
    private static final String COLUMN_USER_PASSWORD = "user_password";

    public SQLiteDatabase myDataBase;


    public DatabaseHelper(Context context)  {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.mycontext=context;
        boolean dbexist = checkdatabase();
        if (dbexist) {
            System.out.println("Database exists");
            opendatabase();
        } else {
            System.out.println("Database doesn't exist");
            createdatabase();
        }
    }
    private void copydatabase() throws IOException {
        //Open your local db as the input stream
        InputStream myinput = mycontext.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 byte to inputfile to outputfile
        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();
    }

    private boolean checkdatabase() {

        boolean checkdb = false;
        try {
            String myPath = DB_PATH + DATABASE_NAME;
            File dbfile = new File(myPath);
            checkdb = dbfile.exists();
        } catch(SQLiteException e) {
            System.out.println("Database doesn't exist");
        }
        return checkdb;
    }
    public void opendatabase() throws SQLException {
        //Open the database
        String mypath = DB_PATH + DATABASE_NAME;
        System.out.println(DB_PATH);
        myDataBase = SQLiteDatabase.openDatabase(mypath, null, SQLiteDatabase.OPEN_READWRITE);
        if (myDataBase.isOpen()) {
            System.out.println("Database is open");

        }

    }

    public void createdatabase()  {
        boolean dbexist = checkdatabase();
        if(dbexist) {
            System.out.println(" Database exists.");

        } else {
            this.getReadableDatabase();
            try {
                copydatabase();
            } catch(IOException e) {
                throw new Error("Error copying database");
            }
        }
    }


    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (newVersion >oldVersion){
            try{
                copydatabase();
            }catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * This method will return if user is in db or not 
     *
     * @param name
     * @param password
     * @return true/false
     */
    public boolean checkUser(String name, String password) {


        // array of columns to fetch
        String[] columns = {
                COLUMN_USER_ID
        };
        opendatabase();
        myDataBase = getReadableDatabase();
        // selection criteria
        String selection = COLUMN_USER_NAME + " = ?" + " AND " + COLUMN_USER_PASSWORD + " = ?";

        // selection arguments
        String[] selectionArgs = {name, password};

        // query user table with conditions
        /**
         * Here query function is used to fetch records from user table this function works like we use sql query.
         * SQL query equivalent to this query function is
         * SELECT user_id FROM user WHERE user_email = 'jack@androidtutorialshub.com' AND user_password = 'qwerty';
         */
        Cursor cursor = myDataBase.query(TABLE_USER, //Table to query
                columns,                    //columns to return
                selection,                  //columns for the WHERE clause
                selectionArgs,              //The values for the WHERE clause
                null,                       //group the rows
                null,                       //filter by row groups
                null);                      //The sort order

        int cursorCount = cursor.getCount();

        cursor.close();
        myDataBase.close();
        if (cursorCount > 0) {
            return true;
        }

        return false;
    }

}

Answer 1

我决定使用json来保存我的数据，用户将通过wifi访问。

26.02.2017 - 外部Sqlite＆＃39;用户＆＃39;找不到表但已复制DB。 [Android的]

1 个答案: