Delphi TFloatField.DisplayFormat for numeric fields less than 1.0

问题

This is my procedure.

procedure format_integer_field(Atable: TDataSet);
 var i: integer;
begin
 if Atable.Active then
 if Atable.FieldCount > 0 then
 with Atable do
 begin
  for i:= 0 to FieldCount-1 do
  if (Fields[i] is TIntegerField) then
  begin
   (Fields[i] as TIntegerField).DisplayFormat := '###,###';
   (Fields[i] as TIntegerField).EditFormat := '#';
  end
  else
   if (Fields[i] is TFloatField) then
  begin
   (Fields[i] as TFloatField).DisplayFormat := '###,###.##';
   (Fields[i] as TFloatField).EditFormat := '#.##';
  end;
 end;
end;

This is work fine until a number like "0.9" has been entered and result will be ".9". How can I have thousand separator and zero before floating point that smaller than "1".

回答1:

The format you need is ###,##0.0#

回答2:

Try (Fields[i] as TFloatField).DisplayFormat := '##0,000.00';

As you did read in documentation at http://docwiki.embarcadero.com/RADStudio/XE3/en/Using_Default_Formatting_for_Numeric,_Date,_and_Time_Fields it says

Default formatting is performed by the following routines:

FormatFloat -- TFloatField, TCurrencyField

And how you did read in the following documentation pages

http://docwiki.embarcadero.com/Libraries/XE3/en/System.SysUtils.FormatFloat
http://docwiki.embarcadero.com/Libraries/XE3/en/Data.DB.TNumericField.DisplayFormat

the documentation quotes

0 -> Digit placeholder. If the value being formatted has a digit in the position where '0' appears in the format string, then that digit is copied to the output string. Otherwise, a '0' is stored in that position in the output string.

# -> Digit placeholder. If the value being formatted has a digit in the position where '#' appears in the format string, then that digit is copied to the output string. Otherwise, nothing is stored in that position in the output string.

So by using "#" in the formatting pattern you tell Delphi "i do not need any digits (and thousands separators with them) in this place, but you might put them if you want" - and since Delphi does not want to put leading zeros - you don't have any. However, if you really need those digits and the thousands separator with them, you put "0" instead of "#" and that way you tell Delphi "the digits just need to be here, whether you want to put them or not"

来源：https://stackoverflow.com/questions/21399729/delphi-tfloatfield-displayformat-for-numeric-fields-less-than-1-0

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