firemonkey threading on android show a black page - firemonkey

Question

i used a httpd to request some data from internet
function requestToServer(lParamList: TStringList) : string;
var
userDataString : string;
lHTTP: TIdHTTP;
serverResponce : string;
aobj: ISuperObject;
begin
application.ProcessMessages;
TThread.CreateAnonymousThread(
procedure
begin
lHTTP := TIdHTTP.Create(nil);
try
serverResponce := lHTTP.Post('http://domain.com/mjson.php', lParamList);
application.ProcessMessages;
aobj:= SO(serverResponce);
try
X := aobj['dta'].AsArray;
Except
form2.Memo1.Lines.Add('errr');
end;
if aobj['result'].AsString = 'lr_102' then
begin
form2.Label3.Text:='Saved token expired.';
form2.Rectangle2.Visible:=true;
end
else if aobj['result'].AsString = 'lr_103' then
begin
form2.Label3.Text:='Auto login.';
//load device data
form2.allDeviceListData := X;
form2.Hide;
form1.show;
end;
// globalReachedServer:=true;
finally
lHTTP.Free;
lParamList.Free;
end;
TThread.Synchronize(nil,
procedure
begin
end);
end
).Start();
end;
but after reach this function
the application show a black page and dont do anything until manually close
how can i do a web request at the background and with out hanging on fire-monkey !?
what a bout using REST is it better to access web service's?

Answer 1

Your code is not thread-safe. Your thread is directly accessing UI controls without synchronizing with the main UI thread. That alone can cause problems.
Also, all of the variables declared in the var section of requestToServer() should be moved into the var section of the anonymous procedure instead, since requestToServer() does not use them, so they can be completely local to the thread instead. The only thing the anonymous procedure should be capturing is the lParamList content.
Try something more like this:
function requestToServer(lParamList: TStringList) : string;
var
Params: TStringList;
Thread: TThread;
begin
Params := TStringList.Create;
try
Params.Assign(lParamList);
except
Params.Free;
raise;
end;
TThread.CreateAnonymousThread(
procedure
var
lHTTP: TIdHTTP;
serverResponce : string;
aObj: ISuperObject;
begin
try
try
lHTTP := TIdHTTP.Create(nil);
try
serverResponce := lHTTP.Post('http://domain.com/mjson.php', lParamList);
aObj := SO(serverResponce);
if aObj['result'].AsString = 'lr_102' then
begin
TThread.Queue(nil,
procedure
begin
form2.Label3.Text := 'Saved token expired.';
form2.Rectangle2.Visible := true;
end
);
end
else if aObj['result'].AsString = 'lr_103' then
begin
X := aObj['dta'].AsArray;
TThread.Queue(nil,
procedure
begin
form2.Label3.Text := 'Auto login.';
//load device data
form2.allDeviceListData := X;
form2.Hide;
form1.show;
end
);
end;
// globalReachedServer := true;
finally
lHTTP.Free;
end;
finally
Params.Free;
end;
except
TThread.Queue(nil,
procedure
begin
form2.Memo1.Lines.Add('errr');
end
);
end;
end
).Start;
end;