新闻类缓存的SqlDao

MyHelp myHelp;

public SqlDao(Context context) {
    this.myHelp = new MyHelp(context);

}
public void insert(String json,String Url)
{
    SQLiteDatabase db = myHelp.getWritableDatabase();
    db.delete("toutiao","url=?",new String[]{Url});
    ContentValues values=new ContentValues();
    values.put("json",json);
    values.put("url",Url);
    db.insert("toutiao",null,values);
    db.close();
}
public String select(String url){
    SQLiteDatabase db = myHelp.getWritableDatabase();
    Cursor cursor = db.rawQuery("select * from toutiao where url=?", new String[]{url});
    if (cursor.moveToNext())
    {
        String string = cursor.getString(cursor.getColumnIndex("json"));
        return string;
    }

    return null;
}