Android 如何从现有SQLite数据库获取数据

我正在尝试使用android studio中现有的sqlite数据库。我想查看表的数据，但我的get（）方法不起作用。“select*from table”表示没有具有该名称的表。但是安卓设备监视器说数据库是在文件夹/数据中创建的 你能帮帮我吗。这是我的密码

这是databaseHelper类

package com.example.alex.probando;

import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Created by alex on 7/1/2016.
 */
public class DataBaseHelper extends SQLiteOpenHelper {

//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.example.alex.probando/databases/";

private static String DB_NAME = "german.db";

public static final String TABLE_NAME = "german";

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 DataBaseHelper(Context context) {

    super(context, DB_NAME, null, 1);
    this.myContext = context;
}

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

    boolean dbExist = checkDataBase();

    if(dbExist){
        //do nothing - database already exist
    }else{

        //By calling this method and empty database will be created into the default system path
        //of your application so we are gonna be able to overwrite that database with our database.
        this.getReadableDatabase();

        try {

            copyDataBase();

        } catch (IOException e) {

            throw new Error("Error copying database");

        }
    }

}

/**
 * Check if the database already exist to avoid re-copying the file each time you open the application.
 * @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){

        //database does't exist yet.

    }

    if(checkDB != null){

        checkDB.close();

    }

    return checkDB != null ? true : false;
}

/**
 * Copies your database from your local assets-folder to the just created empty database in the
 * system folder, from where it can be accessed and handled.
 * This is done by transfering bytestream.
 * */
private void copyDataBase() throws IOException{

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

    // Path to 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 inputfile to the 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();

}

public void openDataBase() throws SQLException {

    //Open the database
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

}

@Override
public synchronized void close() {

    if(myDataBase != null)
        myDataBase.close();

    super.close();

}

@Override
public void onCreate(SQLiteDatabase db) {

}

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

}

// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.

public Cursor getAllData() {
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
    return res;
}

}

这是主要的活动

package com.example.alex.probando;

import android.database.Cursor;
import android.database.SQLException;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    DataBaseHelper myDb;
    TextView txt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myDb = new DataBaseHelper(this);
        txt = (TextView) findViewById(R.id.txt);

        try {

            myDb.createDataBase();

        } catch (IOException ioe) {

            throw new Error("Unable to create database");

        }

        try {

            myDb.openDataBase();

        }catch(SQLException sqle){

            throw sqle;

        }


    }

    public void ver (View view) {
        Cursor res = myDb.getAllData();
    if(res.getCount() == 0) {
        showMessage("Error", "Nothing found");
        return;
    }
    StringBuffer buffer = new StringBuffer();
    while (res.moveToNext()) {
        buffer.append("Id : " + res.getString(0) + "\n");
        buffer.append("English: " + res.getString(1) + "\n");
        buffer.append("German: " + res.getString(2) + "\n\n");
    }

    showMessage("German",buffer.toString());
    }

    public void showMessage(String title, String message){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(message);
        builder.show();
    }
}