Android studio da sql kullanarak bir proje yapmaya çalışıyorum ama ilk ekranda butona tıkladığımda unfortunately has stopped hatası alıyorum.


package com.example.companytodo;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.io.IOException;
public class login extends AppCompatActivity {
    DatabaseHelper dbHelper;
    Context context = this;
    EditText name, pass;
    Button buttonLog;
    Cursor cursor;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.log_in);
        dbHelper = new DatabaseHelper(context);
        try {
            dbHelper.createDataBase();
            dbHelper.openDataBase();
        } catch (IOException e) {
            e.printStackTrace();
        }
        name = (EditText) findViewById(R.id.editTextName);
        pass = (EditText) findViewById(R.id.editTextPass);
        buttonLog = (Button) findViewById(R.id.buttonLog);
        buttonLog.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                cursor = dbHelper.getDatabase().query("register", new String[]{ "id","isAdmin","name","surname","username","password" },
                        "username = ?, password=? ", new String[]{String.valueOf(name), String.valueOf(pass)},
                        null, null, null);
                if (name.getText().toString().equals("") || pass.getText().toString().equals("")) {
                    Toast.makeText(getApplicationContext(), "Username and Password can't be empty", Toast.LENGTH_LONG).show();
                    return;
                }
                if (cursor != null) {
                    if (cursor.getCount() > 0) {
                        Toast.makeText(login.this, "Logged In succesfully!", Toast.LENGTH_LONG).show();
                        if (cursor.getColumnIndex("isAdmin") == 0) {
                            Intent intent = new Intent(login.this, userToDo.class);
                            startActivity(intent);
                        } else {
                            Intent intent = new Intent(login.this, adminToDo.class);
                            startActivity(intent);
                        }
                    } else {
                        Toast.makeText(login.this, "Invalid username or password!", Toast.LENGTH_SHORT).show();
                    }
                }
            }
        });
    }
}
package com.example.companytodo;
import android.annotation.SuppressLint;
import android.content.Context;
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;
public class DatabaseHelper extends SQLiteOpenHelper {
    private static final int VERSION = 1;
    @SuppressLint("SdCardPath")
    private static final String DB_PATH = "/data/data/com.example.companytodo/databases/";
    private static final String DB_NAME = "database";
    private SQLiteDatabase sqLiteDatabase;
    private Context mContext;
    public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, VERSION);
        mContext = context;
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
    public void createDataBase() throws IOException {
        boolean dbExist = checkDataBase();
        if (!dbExist){
            this.getReadableDatabase();
            try {
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Veritabanı kopyalanamadı");
            }
        }
    }
    private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
        } catch (SQLiteException e) {
        }
        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null ? true : false;
    }
    private void copyDataBase() throws IOException {
        InputStream myInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream myOutput = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }
        myOutput.flush();
        myOutput.close();
        myInput.close();
    }
    public SQLiteDatabase getDatabase(){
        return sqLiteDatabase;
    }
    public void openDataBase() throws SQLException {
        String myPath = DB_PATH + DB_NAME;
        sqLiteDatabase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    }
    @Override
    public synchronized void close() {
        if (sqLiteDatabase != null)
            sqLiteDatabase.close();
        super.close();
    }
}