function GetMethod(HTTP: TIdHTTP; Url: String; Max: Integer): String;
var
  RespData: TStringStream;
begin
  RespData := TStringStream.Create('', TEncoding.UTF8);
  try
    try
      HTTP.Get(Url, RespData);
      HTTP.Request.Referer := Url;
      Result := RespData.DataString;
    except
      Dec(Max);
      if Max = 0 then
      begin
        Result := '';
        Exit;
      end;
      Result := GetMethod(Url, Max);
    end;
  finally
    FreeAndNil(RespData);
  end;
end;

uses System.JSON;
const
TokenUrl = 'https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=%s&secret=%s';

procedure GetToken(AppID, AppSecret: String);

var
  Url: string;
  J: TJSONObject;
begin
  Url := Format(TokenUrl, [AppID, AppSecret]);//AppID,AppSecret在你的公众平台上可以查到
  J := TJSONObject.ParseJSONValue(GetMethod(Url, 1)) as TJSONObject;
  try
    if J.Count > 0 then
    begin
      Access_Token := J.GetValue('access_token').Value;//这就是后面做什么都要用到的access_token，每天获取的次数是每天2000次，所以不能每次用都重新获取
      Expires_IN := J.GetValue('expires_in').Value.ToInteger;//access_token的过期时间，7200秒，所以要在过期前重新获取
    end;
  finally
    J.Free;
  end;
end;