android SQLite的使用

public class NewsDBApi extends SQLiteOpenHelper{    private static final String DB_NAME = "newsData.db"; //数据库名称    private static final int version = 1; //数据库版本    private SQLiteDatabase database;    private ArrayList<Data_Map_News> list = new ArrayList<Data_Map_News>();    public NewsDBApi(Context context){        super(context,DB_NAME,null,version);    }    /*   **返回数据表所有的数据   * @params tablename 数据库表名   * @return list   */    public ArrayList<Data_Map_News> queryData(String tablename){        database = this.getReadableDatabase();        //Log.i("查询数据库路径：",database.getPath());        Cursor c = database.query(tablename,null,null,null,null,null,"mTime desc ");//查询并获得游标        while (c.moveToNext()){                int id = c.getInt(c.getColumnIndex("_id"));                String mTitle = c.getString(c.getColumnIndex("mTitle"));                String mFrom = c.getString(c.getColumnIndex("mFrom"));                String mImage = c.getString(c.getColumnIndex("mImage"));                String mUrl = c.getString(c.getColumnIndex("mUrl"));                long mTime = c.getLong(c.getColumnIndex("mTime"));                list.add(new Data_Map_News(mTitle,new Date(mTime),mFrom,mImage,mUrl));            }        c.close();        return  list;    }    /*    **返回数据表最近更新的数据    * @params tablename 数据库表名    * @params lasttime 上次最后插入的一条数据    * @return list    */    public ArrayList<Data_Map_News> queryUpdateData(String tablename,long lasttime){        database = this.getReadableDatabase();        //Log.i("查询数据库路径：",database.getPath());        Cursor c = database.rawQuery("select * from "+tablename+" where "+lasttime+"> mTime order by mTime desc",null);        while (c.moveToNext()){            int id = c.getInt(c.getColumnIndex("_id"));            String mTitle = c.getString(c.getColumnIndex("mTitle"));            String mFrom = c.getString(c.getColumnIndex("mFrom"));            String mImage = c.getString(c.getColumnIndex("mImage"));            String mUrl = c.getString(c.getColumnIndex("mUrl"));            long mTime = c.getLong(c.getColumnIndex("mTime"));            list.add(new Data_Map_News(mTitle,new Date(mTime),mFrom,mImage,mUrl));        }        c.close();        return  list;    }    /*     **返回数据表的数量     * @params tablename 数据库表名     * @return int     */    public int querysum(String tablename){        database = this.getReadableDatabase();        Cursor c = database.rawQuery("select * from "+tablename,null);        Log.i("查询数据数量：",c.getCount()+"");        return  c.getCount();    }    /*     **查询最新插入数据库的一条数据     * @params tablename 数据库表名     * @return long     */    public long querylast(String tablename){        ArrayList<Data_Map_News> list1 = queryData(tablename);       // Log.i("查询数据库：",list1.get(0).getmTime().getTime()+"");        return list1.get(0).getmTime().getTime();    }    /*   **插入数据   * @params tablename 数据库表名   * @params mTime和strings 需要插入的数据   * @return int   */    public void insertData(String tablename,long mTime,String... strings){        database = this.getWritableDatabase();        //Log.i("插入数据库路径：",database.getPath());        //实例化一个ContentValues用来装载待插入的数据cv.put("username","Jack Johnson");//添加用户名        ContentValues cv = new ContentValues();            cv.put("mTitle",strings[0]);            cv.put("mFrom",strings[1]);            cv.put("mImage",strings[2]);            cv.put("mUrl",strings[3]);            cv.put("mTime",mTime);            database.insert(tablename,null,cv);//执行插入操作    }    /*      ** 根据mTime字段删除数据     */    public void deleteData(long mTime, String tablename){        database = this.getWritableDatabase();        String sql = "delete from "+tablename+" where mTime <= "+mTime;//删除操作的SQL语句        database.execSQL(sql);//执行删除操作    }    /*     **创建多个数据表     */    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("create table t_sectors( _id integer primary key autoincrement" +                ",mTitle not null,mFrom not null,mTime not null,mImage not null,mUrl not null)");        db.execSQL("create table t_domestic( _id integer primary key autoincrement" +                ",mTitle not null,mFrom not null,mTime not null,mImage not null,mUrl not null)");            }    /*      **更新数据库     */    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//        String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;//        db.execSQL(sql);//        onCreate(db);    }    /*     * 删除数据库     */    public static void  deleteDB(String dbName,Context context){        File file = new File("/data/data/"+context.getPackageName()+"/databases/"+dbName);        file.delete();    }}