1.创建MyDB.class类并继承SQLiteOpenHelper，然后实现onCreate,onUpgrade的方法并创建构造器。
2.下面是我写的一个类，写的不够好，有空再优化下。

import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;
import android.content.Context;
import java.util.HashMap;
import android.content.ContentValues;
import java.util.List;
import android.database.Cursor;
import java.util.ArrayList;

public class MyDb extends SQLiteOpenHelper {

    @Override
    public void onCreate(SQLiteDatabase p1) {
                   //创建user表
        p1.execSQL("CREATE TABLE user"+
                   //添加id自增字段
                   "(id INTEGER primary key,"+
                   //添加整数型字段
                   "type INTEGER not null,"+
                   //添加文本类型字段
                   "content TEXT not null,"+
                   //添加自动添加时间字段
                   "date timestamp not null default (datetime('now','localtime')));");
        
    }

    @Override
    public void onUpgrade(SQLiteDatabase p1, int p2, int p3) {
        //删除表
        p1.execSQL("DROP TABLE IF EXISTS user");
    }
    // 1. 创建 or 打开 可读/写的数据库（通过 返回的SQLiteDatabase对象 进行操作）
    private SQLiteDatabase sql = getWritableDatabase();

    public MyDb(Context context,String path)
    {
        //   context   数据库文件地址
        super(context, path, (SQLiteDatabase.CursorFactory) null, 1);
    }
    
    //删除
    public void delete(int i)
    {
        this.sql.execSQL("DELETE  FROM  user WHERE id=" + i);
        
    }
    //添加
    public boolean add(HashMap<String,Object> insertBean)
    {
        ContentValues contentValues = new ContentValues();
        contentValues.put("type", new Integer( insertBean.get("type")));
        contentValues.put("content",(String) insertBean.get("content"));
        if (this.sql.insert("user", (String) null, contentValues) == ((long) -1))
        {
            return false;
        }
        return true;
    }
    //更新
    public void update(int i, String txt)
    {
        ContentValues contentValues = new ContentValues();
        contentValues.put("content", txt);
        this.sql.update("user", contentValues, "id=?", new String[]{new StringBuffer().append(i).append("").toString()});
    }

    //查询所有
    public List<HashMap<String,Object>> getAll()
    {

        ArrayList<HashMap<String,Object>> arrayList = new ArrayList<HashMap<String,Object>>();
        Cursor query = this.sql.query("user", (String[]) null, (String) null, (String[]) null, (String) null, (String) null, (String) null);
        while (query.moveToNext())
        {
            HashMap<String,Object> itemBean = new HashMap<String,Object>();
            itemBean.put("id",query.getInt(query.getColumnIndex("id")));
            itemBean.put("type",query.getInt(query.getColumnIndex("type")));
            itemBean.put("content", query.getString(query.getColumnIndex("content")));
            itemBean.put("date",query.getString(query.getColumnIndex("date")));
            arrayList.add(itemBean);
        }
        return arrayList;
    }
    //查询最后一个
    public HashMap getlastOne()
    {
        HashMap<String,Object> itemBean = new HashMap<String,Object>();
        Cursor query = this.sql.rawQuery("SELECT * FROM user WHERE id = (SELECT MAX(id) FROM user)", null);
        if (query.moveToNext())
        {
            itemBean.put("type",query.getInt(query.getColumnIndex("type")));
            itemBean.put("id",query.getInt(query.getColumnIndex("id")));
            itemBean.put("content", query.getString(query.getColumnIndex("content")));
            
        }
        return itemBean;
    }
    //分页
    public ArrayList<HashMap<String,Object>> limit(int page){
        ArrayList<HashMap<String,Object>> arrylist=new ArrayList<HashMap< String,Object>>();
        String sql="select * from user order by id limit 10 offset "+page;
        Cursor query = this.sql.rawQuery(sql, null);
        while (query.moveToNext())
        {
            HashMap<String,Object> itemBean = new HashMap<String,Object>();
            itemBean.put("type",query.getInt(query.getColumnIndex("type")));
            itemBean.put("content", query.getString(query.getColumnIndex("content")));
            arrylist.add(itemBean);
        }
        return arrylist;
    }
    
}