Open and read a file in firemonkey - delphi

Question

What is wrong in this code ? I don't understend, if I remove the "Try" my app dont open, and if don't remove always appear "need login" ...
procedure TF_login.FormActivate(Sender: TObject);
var
Result: Integer;
TextFile: TStringList;
VarArquivo: string;
text: string;
dataI, dataF : string;
begin
TextFile := TStringList.Create;
VarArquivo := System.IOUtils.TPath.GetDocumentsPath + PathDelim + 'Limit.txt';
try
TextFile.LoadFromFile(VarArquivo);
text := TextFile.Text;
// ShowMessage(TextFile.Text); // there is the text
// ShowMessage(text); // there is the text
dataI := FormatDateTime('dd/mm/yyyy', Now);
dataF := FormatDateTime('dd/mm/yyyy', StrToDate(text));
Result := CompareDate(StrToDate(dataI), StrToDate(dataF));
ShowMessage(dataF +' data f');
ShowMessage(dataI +' data I');
if ( Result = LessThanValue ) then
begin
ShowMessage('data F low');
end
else
begin
ShowMessage('data F high');
F_inicio.Show;
end;
FreeAndNil(TextFile);
except on E:
Exception do ShowMessage('An error happened!' + sLineBreak + '[' +
E.ClassName + '] ' + E.Message);
end;
end;
The error : [EConvertError] '09/11/2019' is not a valid date
to create the file, i do:
procedure TF_login.btn_entrarClick(Sender: TObject);
var
data : tdatetime;
Resposta, data_s: string;
begin
PathFile := System.IOUtils.TPath.GetDocumentsPath;
NameFile := 'Limit.txt';
data := Now; //data actual
data := IncMonth(data, 2);
data_s := FormatDateTime('dd/mm/yyyy', data);
TFile.WriteAllText(TPath.Combine(PathFile, NameFile), data_s );
F_inicio.Show;
end;
The file exists, because the first (and second) ShowMessage (what is commented) show me the "09/11/19" but the third and fourth not appear to me...
OBS: Delphi 10.3 (RIO), Plataform: Android

Answer 1

There are a couple of things that you should change in your code:
procedure TF_login.FormActivate(Sender: TObject);
var
TextFile: TStringList;
VarArquivo: string;
text: string;
dataI, dataF : string;
begin
// If an exception (unlikely, but on principle) happens in your VarArquivo
// assignment, then the original version will leak the allocated TStringList.
// Always place the TRY right after allocation of a memory block. That way
// you ensure that the FINALLY block will always release the allocated
// memory. Also, always include a FINALLY block to release the memory. Don't
// count on your code to reach the FreeAndNIL code (it doesn't in this
// instance, as you can see) to make sure that you actually release the
// memory.
VarArquivo := System.IOUtils.TPath.GetDocumentsPath + PathDelim + 'Limit.txt';
TextFile := TStringList.Create;
try // - except
try // - finally
TextFile.LoadFromFile(VarArquivo);
text := TextFile.Text;
// ShowMessage(TextFile.Text); // there is the text
// ShowMessage(text); // there is the text
dataI := FormatDateTime('yyyy/mm/dd', Date);
dataF := FormatDateTime('yyyy/mm/dd', StrToDate(text));
ShowMessage(dataF +' data f');
ShowMessage(dataI +' data I');
if ( dataF < dataI ) then
begin
ShowMessage('data F low');
end
else
begin
ShowMessage('data F high');
F_inicio.Show;
end;
finally
FreeAndNil(TextFile);
end
except
// NEVER just "eat" an exception. Especially not while developing the
// application.
// Always either log the exception or show it to the user.
on E:Exception do ShowMessage('Exception '+E.ClassName+': '+E.Message+#13#10+
'need login');
end;
end;
Now - if you do this, what exception and error message is shown. This is needed in order to properly diagnose the error. Perhaps you can even figure it out for yourself when you see what exactly goes wrong...