int id;

    String code;

    String name;

    int qty;

import java.util.ArrayList;

import java.util.HashMap;

import android.content.ContentValues;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

public class DBHelper extends SQLiteOpenHelper {

    public final static String DB_NAME = "test.db";

    public final static int VERSION = 1;

    private static DBHelper instance = null;

    private SQLiteDatabase db;

    public static DBHelper getInstance(Context context) {

        if (instance == null) {

            instance = new DBHelper(context);

        }

        return instance;

    }

    private void openDatabase() {

        if (db == null) {

            db = getWritableDatabase();

        }

    }

    private DBHelper(Context context) {

        super(context, DB_NAME, null, VERSION);

    }

    /** 第一次安装程序后创建数据库 */

    @Override

    public void onCreate(SQLiteDatabase db) {

        db.execSQL("create table product (_id integer primary key autoincrement,code text,name text,qty Integer )");

    }

    /** 版本升级时，先删除原有的数据库，再重新创建数据库 */

    @Override

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

        db.execSQL("drop table if exist product");

        onCreate(db);

    }

    /** 添加一条数据 */

    public long saveLamp(Product pro) {

        ContentValues value = new ContentValues();

        value.put("code", pro.getCode());

        value.put("name", pro.getName());

        value.put("qty", pro.getQty());

        return db.insert("product", null, value);

    }

    /** 根据id删除数据 */

    public int deleteLamp(int id) {

        return db.delete("product", "_id=?", new String[] { String.valueOf(id) });

    }

    /** 根据id更新数据 */

    public int updateLamp(Product pro, int id) {

        ContentValues value = new ContentValues();

        value.put("code", pro.getCode());

        value.put("name", pro.getName());

        value.put("qty", pro.getQty());

        return db.update("product", value, "_id=?", new String[] { String.valueOf(id) });

    }

    /** 查询所有数据 */

    public ArrayList<HashMap<String, Object>> getLampList() {

        openDatabase();

        Cursor cursor = db.query("product", null, null, null, null, null, null);

        ArrayList<HashMap<String, Object>> list = new ArrayList<HashMap<String, Object>>();

        while (cursor.moveToNext()) {

            HashMap<String, Object> map = new HashMap<String, Object>();

            map.put("id", cursor.getInt(cursor.getColumnIndex("_id")));

            map.put("code", cursor.getString(cursor.getColumnIndex("code")));

            map.put("name", cursor.getString(cursor.getColumnIndex("name")));

            map.put("qty", cursor.getString(cursor.getColumnIndex("qty")));

            list.add(map);

        }

        return list;

    }

    /** 根据编码查询数据 */

    public Product getALamp(String code) {

        openDatabase();

        Cursor cursor = db.query("product", null, "code=?", new String[] { code }, null, null, null);

        Product pro = new Product();

        while (cursor.moveToNext()) {

            pro.setId(cursor.getInt(cursor.getColumnIndex("_id")));

            pro.setCode(cursor.getString(cursor.getColumnIndex("code")));

            pro.setName(cursor.getString(cursor.getColumnIndex("name")));

            pro.setQty(cursor.getInt(cursor.getColumnIndex("qty")));

        }

        return pro;

    }

    /** 查询有多少条记录 */

    public int getLampCount() {

        openDatabase();

        Cursor cursor = db.query("product", null, null, null, null, null, null);

        return cursor.getCount();

    }

}

import java.util.ArrayList;

import java.util.HashMap;

import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

public class MainActivity extends Activity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        exec();// 测试数据

    }

    private void exec() {

        /** 添加数据 */

        Product product1 = new Product("pingguo", "红富士苹果", 100);

        long sucess1 = DBHelper.getInstance(MainActivity.this).saveLamp(product1);

        Log.d("test", "sucess=" + sucess1);

        if (sucess1 > 0) {

            // "添加成功！"

        } else {

            // "添加失败，请重新操作！"

        }

        /** 修改数据 */

        Product product2 = new Product("pingguo", "红富士苹果", 100);

        int updateId = 5;

        int sucess2 = DBHelper.getInstance(MainActivity.this).updateLamp(product2, updateId);

        if (sucess2 > 0) {

            // "修改成功！"

        } else {

            // "修改失败，请重新操作！"

        }

        /** 删除数据 */

        int deleteId = 5;

        int sucess = DBHelper.getInstance(MainActivity.this).deleteLamp(deleteId);

        if (sucess > 0) {

            // "删除成功！"

        } else {

            // "删除失败！"

        }

        /** 获取表记录数 */

        int count = DBHelper.getInstance(MainActivity.this).getLampCount();

        /** 获取所有数据 */

        ArrayList<HashMap<String, Object>> data = DBHelper.getInstance(MainActivity.this).getLampList();

    }

}