Android database app freezing and then crashing when I run it on a device

This is a simple database app which stores something in a table(on button click) and deletes(on button click). On installing the app on device(lollipop), main activity pops up, but as soon as I enter some text in the textfield and click the button to save it to database, the app freezes and force closes after some time.Also if I try running the app again then the main activity doesn't start and the app force closes.

This is the main activity,

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;



public class MainActivity extends ActionBarActivity {

    EditText myinput;
    TextView mytext;
    MyDBHandler dbhandler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        myinput =(EditText) findViewById(R.id.myinput);
        mytext =(TextView) findViewById(R.id.mytext);
        dbhandler= new MyDBHandler(this, null, null, 1);
        printDatabase();
    }

    //add product to database

    public void addstuff(View view)
    {
        products product = new products(myinput.getText().toString());
        dbhandler.addProduct(product);
        printDatabase();

    }

    //delete items from database

    public void deletestuff(View view)
    {
        String inputtext= myinput.getText().toString();
        dbhandler.deleteProduct(inputtext);
        printDatabase();


    }

    public void printDatabase()
    {
        String dbString= dbhandler.databaseToString();
        mytext.setText(dbString);
        myinput.setText("");
    }

}

This is the database handler class

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.Cursor;
import android.content.Context;
import android.content.ContentValues;


public class MyDBHandler extends SQLiteOpenHelper{

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "products.db";
    public static final String TABLE_PRODUCTS = "products";
    public static final String COLUMN_ID ="_id";
    public static final String COLUMN_PRODUCTNAME ="productname";


    public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, DATABASE_NAME, factory, DATABASE_VERSION);
    }


    @Override
    public void onCreate(SQLiteDatabase db) {

        String query= "CREATE TABLE " + TABLE_PRODUCTS + "(" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT , " +
                COLUMN_PRODUCTNAME + " TEXT " +
                ");";
        db.execSQL(query);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TALE IF EXISTS "+TABLE_PRODUCTS);
        onCreate(db);
    }

    //add a new row to the database
    public void addProduct(products product)
    {
        ContentValues values = new ContentValues();
        values.put(COLUMN_PRODUCTNAME, product.get_productname());
        SQLiteDatabase db= getWritableDatabase();
        db.insert(TABLE_PRODUCTS, null, values);
        db.close();
    }

    //delete product from the database
    public void deleteProduct(String productname)
    {
        SQLiteDatabase db= getWritableDatabase();
        db.execSQL("DELETE FROM "+ TABLE_PRODUCTS + " WHERE " + COLUMN_PRODUCTNAME + " =\"" + productname + "\";" );
    }

    //printing out the database as a string

    public String databaseToString()
    {
        String dbString ="";
        SQLiteDatabase db= getWritableDatabase();
        String query = "SELECT * FROM "+ TABLE_PRODUCTS + " WHERE 1";

        //CURSOR POINTS TO A LOCATION IN THE DATABASE RESULTS
        Cursor c= db.rawQuery(query,null);
        //go to 1st row in your results
        c.moveToFirst();

        while(!c.isAfterLast())
        {
            if(c.getString(c.getColumnIndex("productname"))!=null)
            {
                dbString += c.getString(c.getColumnIndex("productname"));
                dbString += "\n";

            }

        }
        db.close();
        return dbString;

    }



}

this is the products class which I'v used for setting and getting names

public class products {

    private int _id;
    private String _productname;

    public products()
    {

    }

    public products(String productname) {
        this._productname = productname;
    }

    public void set_id(int _id) {
        this._id = _id;
    }

    public void set_productname(String _productname) {
        this._productname = _productname;
    }

    public int get_id() {
        return _id;
    }

    public String get_productname() {
        return _productname;
    }
}