报表生成器FastReport VCL使用实例：将JSON格式的股票报价生成了一份报告

FastReport VCL是用于Delphi，C ++ Builder，RAD Studio和Lazarus的报告和文档创建VCL库。本文是关于它的一个实例：将JSON格式的股票报价生成了一份报告。

您可以点击此处，下载本文教程完整的演示Demo。

根据文档要求，为了获得股票报价，需要使用GET请求“历史记录”

报表生成器FastReport VCL使用实例：将JSON格式的股票报价生成了一份报告

创建一个应用程序并将组件添加到表单中：

 frxReport1: TfrxReport; JSON_DS: TfrxUserDataSet; ButtonConnectToJSON: TButton; Label1: TLabel; Label2: TLabel; Label3: TLabel; ComboBoxName: TComboBox; ComboBoxResolution: TComboBox; DateTimePickerFrom: TDateTimePicker; Label4: TLabel; DateTimePickerTo: TDateTimePicker; ButtonShowReport: TButton; Image1: TImage; Label5: TLabel; StatusBar1: TStatusBar; ButtonDesign: TButton; frxDesigner1: TfrxDesigner; frxChartObject1: TfrxChartObject; frxPDFExport1: TfrxPDFExport;

将项目添加到ComboBoxName和ComboBoxResolution

ComboBoxName.Items := 'GAZP SBER BRENT MOEX ROSN YNDX RUAL';ComboBoxResolution.Items := '1 5 15 30 45 60 120 180 240 D W M';

添加全局变量

var tHTTP: TfrxTransportHTTP; frxJSON: TfrxJSON; Res: String; Symbol,Resolution,FromCandlesHistory,ToCandlesHistory : String; frxJSONArrayT,frxJSONArrayC,frxJSONArrayO, frxJSONArrayH,frxJSONArrayL,frxJSONArrayV: TfrxJSONArray; S: TStringStream;

在ButtonConnectToJSON按钮的Click事件中，编写以下代码：

procedure TFormJSON.ButtonConnectToJSONClick(Sender: TObject);begin frxReport1.LoadFromFile('ChartJSON.fr3'); JSON_DS.RangeEnd := reCount; Symbol := ComboBoxName.Items[ComboBoxName.ItemIndex]; Resolution := ComboBoxResolution.Items[ComboBoxResolution.ItemIndex]; FromCandlesHistory := DateTimeToUnix(DateTimePickerFrom.DateTime).ToString; ToCandlesHistory := DateTimeToUnix(DateTimePickerTo.DateTime).ToString;//Creating a TfrxTransportHTTP Object for a GET Request over HTTPS tHTTP := TfrxTransportHTTP.Create(nil); try//We form a GET request string and get a response in JSON format Res := tHTTP.Get('https://api.bcs.ru/udfdatafeed/v1/historyymbol=' +Symbol+ '&resolution='+Resolution + '&from='+ FromCandlesHistory+ '&to='+ToCandlesHistory);// if JSON is received incorrectly, then load it from the file and display a message in StatusBarr if (Res = '') or (pos('"s":"ok"',Res) = 0) then begin StatusBar1.SimpleText := 'Error loading JSON'; S := TStringStream.Create('', TEncoding.UTF8); try S.LoadFromFile('JSON/'+Symbol+'.json'); finally Res:= S.DataString; FreeAndNil(S); end; StatusBar1.SimpleText := 'Successful JSON loading from file '+Symbol+'.json'; end else begin StatusBar1.SimpleText := 'Successful JSON('+Symbol+') loading'; end;// We load the received JSON from the Res line into the frxJSON object: TfrxJSON frxJSON := TfrxJSON.Create(Res); try if frxJSON.IsValid then begin StatusBar1.SimpleText :=StatusBar1.SimpleText +' /JSON is Valid';// Read arrays if frxJSON.IsNameExists('t') then frxJSONArrayT := TfrxJSONArray.Create(frxJSON.ObjectByName('t')); frxJSONArrayC := TfrxJSONArray.Create(frxJSON.ObjectByName('c')); frxJSONArrayO := TfrxJSONArray.Create(frxJSON.ObjectByName('o')); frxJSONArrayH := TfrxJSONArray.Create(frxJSON.ObjectByName('h')); frxJSONArrayL := TfrxJSONArray.Create(frxJSON.ObjectByName('l')); frxJSONArrayV := TfrxJSONArray.Create(frxJSON.ObjectByName('v'));// Prepare JSON_DS by clearing and adding fields JSON_DS.Fields.Clear; JSON_DS.Fields.Add('Ticker'); JSON_DS.Fields.Add('Date'); JSON_DS.Fields.Add('Time'); JSON_DS.Fields.Add('Open'); JSON_DS.Fields.Add('Close'); JSON_DS.Fields.Add('High'); JSON_DS.Fields.Add('Low'); JSON_DS.Fields.Add('Vol'); JSON_DS.RangeEndCount := frxJSONArrayT.Count; end else StatusBar1.SimpleText :=StatusBar1.SimpleText +' /JSON is Invalid'; finally end; finally end;end;

要通过JSON_DS组件TfrxUserDataSet从数组frxJSONArrayT，frxJSONArrayC，frxJSONArrayO，frxJSONArrayH，frxJSONArrayL，frxJSONArrayV生成报告时获取数据，需要使用OnGetValue事件：

procedure TFormJSON.JSON_DSGetValue(const VarName: string; var Value: Variant);var Item: string; Time : string;begin Item := frxJSONArrayT.GetString(JSON_DS.RecNo); DateTimeToString(Time, 't', UnixToDateTime(StrToInt64(Item))); if VarName = 'Ticker' then begin Value := Symbol; exit; end else if VarName = 'Date' then begin Value := DateToStr(UnixToDateTime(StrToInt64(Item)))+' '+Time; exit; end else if VarName = 'Time' then begin Value := Time; exit; end else if VarName = 'Open' then Item := frxJSONArrayO.GetString(JSON_DS.RecNo) else if VarName = 'Close' then Item := frxJSONArrayC.GetString(JSON_DS.RecNo) else if VarName = 'High' then Item := frxJSONArrayH.GetString(JSON_DS.RecNo) else if VarName = 'Low' then Item := frxJSONArrayL.GetString(JSON_DS.RecNo) else if VarName = 'Vol' then Item := frxJSONArrayV.GetString(JSON_DS.RecNo); Value := Item;end;

接下来，在报表设计器中创建一个模板，将其命名为ChartJSON.fr3并将JSON_DS连接到它。

要显示图表，请使用TeeChart Pro VCL软件包中的Candle系列，并连接到JSON_DS。

接下来，为其余按钮添加Click事件处理程序：

procedure TFormJSON.ButtonDesignClick(Sender: TObject);begin if (Res = '') then ButtonConnectToJSON.Click; frxReport1.DesignReport();end;procedure TFormJSON.ButtonShowReportClick(Sender: TObject);beginif (Res = '') then ButtonConnectToJSON.Click; frxReport1.ShowReport();end;

我们还为ComboBoxName，DateTimePickerFrom和DateTimePickerTo添加了Change事件处理程序：

procedure TFormJSON.ComboBoxNameChange(Sender: TObject);begin ButtonConnectToJSON.Click;end;procedure TFormJSON.DateTimePickerFromChange(Sender: TObject);begin ButtonConnectToJSON.Click;end;procedure TFormJSON.DateTimePickerToChange(Sender: TObject);begin ButtonConnectToJSON.Click;end;

同样，在关闭应用程序时，请不要忘记释放已使用对象的内存。

procedure TFormJSON.FormClose(Sender: TObject; var Action: TCloseAction);begin tHTTP.Free; frxJSON.Free; frxJSONArrayT.Free; frxJSONArrayC.Free; frxJSONArrayO.Free; frxJSONArrayH.Free; frxJSONArrayL.Free; frxJSONArrayV.Free;end;

接下来，运行应用程序。