某些设备上的android中“没有这样的表”问题

Question

I am using an external database in android app and it is working fine on all emulators and on samsung real devices. But when I am checking on the Acer smart phone, my application going crash with following exception:

android.database.sqlite.SQLiteException: no such table:

It is strange to me. I have checked under the data folder in file explorer where my databases and all tables are present.

I am not getting why it is happening.

Please guide me. Thanks in advance

Code of sql helper class is as following:

public class MyDatabaseHelper extends SQLiteOpenHelper {

    // System path of application database.
    private static String DB_PATH = MyApplication.getAppContext()
            .getFilesDir().getParentFile().getPath()
            + "/databases/";
    private static String DB_NAME = "myDB";
    private SQLiteDatabase myDataBase;
    private final Context myContext;

    /**
     * Constructor Takes and keeps a reference of the passed context in order to
     * access to the application assets and resources.
     * 
     * @param context
     */
    public MyDatabaseHelper(Context context) {
        super(context, DB_NAME, null, 1);
        this.myContext = context;
    }

    /**
     * Creates a empty database on the system and rewrites it with own database.
     * 
     */
    public void createDataBase() throws IOException {

        checkDataBase();
        // Creates empty database default system path
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }

    /**
     * Checks if the database already exist to avoid re-copying the file each
     * time whenever the application opened.
     * 
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase() {

        SQLiteDatabase checkDB = null;
        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READONLY);
        } catch (SQLiteException e) {
            e.printStackTrace();
        }

        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null ? true : false;
    }

    /**
     * Copies database from local assets-folder to the just created empty
     * database in the system folder and from where it can be accessed and
     * handled using byte stream transferring.
     * 
     */
    private void copyDataBase() throws IOException {

        // Open local db as the input stream
        InputStream myInput = myContext.getAssets().open(DB_NAME + ".db");

        // Path of the just created empty db
        String outFileName = DB_PATH + DB_NAME;

        // Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        // transfer bytes from the input file to the output file
        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();
    }

    public SQLiteDatabase openDataBase() throws SQLException {

        // Opens the database
        String myPath = DB_PATH + DB_NAME;
        return SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);
    }

    @Override
    public synchronized void close() {
        if (myDataBase != null)
            myDataBase.close();
        super.close();
    }

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

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub
    }
}

Answer 1

Finally I resolved my question.

I just get readable database into the database and close it just after open it again. My complete code is as follows:

 public class MyDatabaseHelper extends SQLiteOpenHelper {

    // System path of application database.
    private static String DB_PATH = MyApplication.getAppContext()
            .getFilesDir().getParentFile().getPath()
            + "/databases/";
    private static String DB_NAME = "myDB";
    private SQLiteDatabase myDataBase;
    private final Context myContext;

    /**
     * Constructor Takes and keeps a reference of the passed context in order to
     * access to the application assets and resources.
     * 
     * @param context
     */
    public MyDatabaseHelper(Context context) {
        super(context, DB_NAME, null, 1);
        this.myContext = context;
    }

    /**
     * Creates a empty database on the system and rewrites it with own database.
     * 
     */
    public void createDataBase() throws IOException {

        checkDataBase();
        SQLiteDatabase db_Read = null;

        // Creates empty database default system path
        db_Read = this.getReadableDatabase();
        db_Read.close();
        try {
            copyDataBase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }

    /**
     * Checks if the database already exist to avoid re-copying the file each
     * time whenever the application opened.
     * 
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase() {

        SQLiteDatabase checkDB = null;
        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READONLY);
        } catch (SQLiteException e) {
            e.printStackTrace();
        }

        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null ? true : false;
    }

    /**
     * Copies database from local assets-folder to the just created empty
     * database in the system folder and from where it can be accessed and
     * handled using byte stream transferring.
     * 
     */
    private void copyDataBase() throws IOException {

        // Open local db as the input stream
        InputStream myInput = myContext.getAssets().open(DB_NAME + ".db");

        // Path of the just created empty db
        String outFileName = DB_PATH + DB_NAME;

        // Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);

        // transfer bytes from the input file to the output file
        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();
    }

    public SQLiteDatabase openDataBase() throws SQLException {

        // Opens the database
        String myPath = DB_PATH + DB_NAME;
        return SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);
    }

    @Override
    public synchronized void close() {
        if (myDataBase != null)
            myDataBase.close();
        super.close();
    }

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

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub
    }
}

I found my answer here :

Answer 2

Probably you have hardcoded the path to the database. For different devices it may be different. Use Envirenment.getExternalStorageDirectory() to create the path to your database.

Answer 3

尝试使用此私有静态String DB_PATH =“/ data / data / your package name / databases /”;