FormatFloat(#,##0.00, var_number) 和 Format('%n', var_number) 舍入到千位时出错

Question

FormatFloat(#,##0.00, var_number) 和 Format('%n', var_number) 为我提供了四舍五入的结果。为什么会这样？我的代码有问题吗？

下面我做了一些Minimum Reproducible Example供大家参考。 我得到的结果是 12 而不是 12,345.00。请让我知道我到底错过了什么地方和什么。

FMX 程序：

unit Unit9;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs,
  FMX.ListView.Types, FMX.ListView.Appearances, FMX.ListView.Adapters.Base,
  FireDAC.Stan.Intf, FireDAC.Stan.Option, FireDAC.Stan.Error, FireDAC.UI.Intf,
  FireDAC.Phys.Intf, FireDAC.Stan.Def, FireDAC.Stan.Pool, FireDAC.Stan.Async,
  FireDAC.Phys, FireDAC.Phys.SQLite, FireDAC.Phys.SQLiteDef,
  FireDAC.Stan.ExprFuncs, FireDAC.FMXUI.Wait, FireDAC.Stan.Param, FireDAC.DatS,
  FireDAC.DApt.Intf, FireDAC.DApt, Data.Bind.EngExt, Fmx.Bind.DBEngExt,
  System.Rtti, System.Bindings.Outputs, Fmx.Bind.Editors, Data.Bind.Components,
  Data.Bind.DBScope, Data.DB, FireDAC.Comp.DataSet, FireDAC.Comp.Client,
  FMX.ListView, FMX.Controls.Presentation, FMX.StdCtrls;

type
  TForm9 = class(TForm)
    lbl1: TLabel;
    lsv1: TListView;
    con1: TFDConnection;
    qryLists: TFDQuery;
    bdr1: TBindSourceDB;
    bdl1: TBindingsList;
    tcf1: TLinkFillControlToField;
    lpfText: TLinkPropertyToField;
    qryInsert: TFDQuery;
    btn1: TButton;
    procedure btn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form9: TForm9;

implementation

{$R *.fmx}

procedure TForm9.btn1Click(Sender: TObject);
begin
  qryInsert.ParamByName('id').AsInteger := 1;
  qryInsert.ParamByName('cur_datetime').AsDateTime := now;
  qryInsert.ParamByName('name').AsString := 'sample';
  qryInsert.ParamByName('size_cont').AsString := 'size_cont';
  qryInsert.ParamByName('qty').AsFloat := 10;
  qryInsert.ParamByName('est_price').AsFloat := 1234.5;
  qryInsert.ParamByName('qty_price').AsString := '10 x 1234.5';
  qryInsert.ParamByName('estimate').AsString := FormatFloat('#,##0.00', 10 * 1234.5); //the result is giving me 12 (the correct one is 12,345.00)
  qryInsert.ExecSQL;
  qryLists.Close;
  qryLists.Open();
end;

end.

FMX 文件：

object Form9: TForm9
  Left = 0
  Top = 0
  Caption = 'Form9'
  ClientHeight = 480
  ClientWidth = 308
  FormFactor.Width = 320
  FormFactor.Height = 480
  FormFactor.Devices = [Desktop]
  DesignerMasterStyle = 0
  object lbl1: TLabel
    Align = Top
    StyledSettings = [Family, Style, FontColor]
    Size.Width = 308.000000000000000000
    Size.Height = 33.000000000000000000
    Size.PlatformDefault = False
    TextSettings.Font.Size = 14.000000000000000000
    TextSettings.HorzAlign = Center
    Text = '5'
    TabOrder = 0
  end
  object lsv1: TListView
    ItemAppearanceClassName = 'TImageListItemBottomDetailAppearance'
    ItemEditAppearanceClassName = 'TImageListItemBottomDetailShowCheckAppearance'
    HeaderAppearanceClassName = 'TListHeaderObjects'
    FooterAppearanceClassName = 'TListHeaderObjects'
    Align = Client
    Size.Width = 308.000000000000000000
    Size.Height = 407.000000000000000000
    Size.PlatformDefault = False
    TabOrder = 1
  end
  object btn1: TButton
    Align = Bottom
    Position.Y = 440.000000000000000000
    Size.Width = 308.000000000000000000
    Size.Height = 40.000000000000000000
    Size.PlatformDefault = False
    TabOrder = 7
    Text = 'btn1'
    OnClick = btn1Click
  end
  object con1: TFDConnection
    Params.Strings = (
      
        'Database=D:\My Project Files. my_projects_aws-rest\project_x_v' +
        '0\application\client\database\smartcart.s3db'
      'LockingMode=Normal'
      'DriverID=SQLite')
    Connected = True
    LoginPrompt = False
    Left = 72
    Top = 24
  end
  object qryLists: TFDQuery
    Active = True
    Connection = con1
    SQL.Strings = (
      'SELECT id, date_created, name, size_cont, qty_price, estimate'
      'FROM lists ORDER BY date_created DESC')
    Left = 112
    Top = 24
  end
  object bdr1: TBindSourceDB
    DataSet = qryLists
    ScopeMappings = <>
    Left = 152
    Top = 24
  end
  object bdl1: TBindingsList
    Methods = <>
    OutputConverters = <>
    Left = 20
    Top = 5
    object tcf1: TLinkFillControlToField
      Category = 'Quick Bindings'
      Control = lsv1
      Track = True
      FillDataSource = bdr1
      AutoFill = True
      FillExpressions = <
        item
          SourceMemberName = 'estimate'
          ControlMemberName = 'Detail'
        end>
      FillHeaderExpressions = <>
      FillBreakGroups = <>
    end
    object lpfText: TLinkPropertyToField
      Category = 'Quick Bindings'
      DataSource = bdr1
      FieldName = 'estimate'
      Component = lbl1
      ComponentProperty = 'Text'
    end
  end
  object qryInsert: TFDQuery
    Connection = con1
    SQL.Strings = (
      'INSERT INTO lists (id, date_created, name, size_cont, '
      '                   qty, est_price, qty_price, estimate) '
      'VALUES (:id, :cur_datetime, :name, :size_cont, '
      '        :qty, :est_price, :qty_price, :estimate);')
    Left = 192
    Top = 24
    ParamData = <
      item
        Name = 'ID'
        DataType = ftInteger
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'CUR_DATETIME'
        DataType = ftDateTime
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'NAME'
        DataType = ftString
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'SIZE_CONT'
        DataType = ftString
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'QTY'
        DataType = ftFloat
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'EST_PRICE'
        DataType = ftFloat
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'QTY_PRICE'
        DataType = ftString
        ParamType = ptInput
        Value = Null
      end
      item
        Name = 'ESTIMATE'
        DataType = ftFloat
        ParamType = ptInput
        Value = Null
      end>
  end
end

更新： TListView 属性截图

Answer 1

根据您的表单定义文件，您的参数定义为 Datatype = ftFloat。

item
  Name = 'ESTIMATE'
  DataType = ftFloat
  ParamType = ptInput
  Value = Null
end>

这意味着您根本不需要使用参数的 AsString 赋值或使用 FormatFloat 转换它，因为您可以直接将值作为浮点值赋值。

qryInsert.ParamByName('estimate').AsFloat := 10 * 1234.5;

这样做不会导致任何舍入错误，因为数据是以正确的值存储的。根本没有四舍五入。

FormatFloat(#,##0.00, var_number) 和 Format('%n', var_number) 舍入到千位时出错

Error on FormatFloat(#,##0.00, var_number) and Format('%n', var_number) Rounding-off to Thousands

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