procedure Tfrm_jz.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
   if (key in ['0'..'9',#8,#13]) then
      begin
       if key=#13 then
          begin
             if length(edit1.Text)>2 then
                edit1.Text:=copy(edit1.Text ,1,(length(edit1.Text)-2))+'.'+copy(edit1.Text ,(length(edit1.Text)-1),2)  ;
             if length(edit1.Text)=2 then
                edit1.Text:='0.'+edit1.Text;
             if length(edit1.Text)=1 then
                edit1.Text:='0.0'+edit1.Text;
             edit2.SetFocus;
          end
      end
   else
      key:=#0;
end;

delphi edit 固定小数位数的实现方法的改进
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procedure Tfrm_jz.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
   if (key in ['0'..'9',#46,#13]) then
      begin
       if (SubStrConut(Edit1.Text,'.')=1) and (key in [#46]) then
             key:=#0;
       if key=#13 then
          begin
          if (pos(',',edit1.text)=0) and (edit1.text<>'') then
             edit1.Text:=formatfloat('#,##0.00',strtofloat(edit1.Text));
          edit2.SetFocus;
          end;
      end
   else if key in [#8]  then
      edit1.text:=''
   else
      key:=#0;
end;

delphi edit 固定小数位数的实现方法的改进(解决无法输入负数的问题)
－－－－－－－－－－－－－－－－－－－－－－－－

procedure Tfrm_jz.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
   if (key in ['0'..'9',#45,#46,#13]) then
      begin
       if (SubStrConut(Edit1.Text,'.')=1) and (key in [#46]) then
             key:=#0;
       if (SubStrConut(Edit1.Text,'-')=1) and (key in [#45]) then
             key:=#0;
       if key=#13 then
          begin
          if (pos(',',edit1.text)=0) and (edit1.text<>'') then
             if (pos('-',edit1.text)=0) or (pos('-',edit1.text)=1) then
             begin
                edit1.Text:=formatfloat('#,##0.00',strtofloat(edit1.Text));
                edit2.SetFocus;
             end;
          end;
      end
   else if key in [#8]  then
      edit1.text:=''
   else
      key:=#0;
end;