不斷通過串口接收設備發送過來的文本資料，通過向設備發送命令並通過接受回應，但是在判斷其中有無某個字串時，函數失效。但是如果把單獨放在另一個中確是可以的。請幫忙，急急急.........

procedure TForm1.MSComm1Comm(Sender: TObject);
var
//buffer: Olevariant;
str: string;
//i: integer;
begin
case MSComm1.CommEvent of
comEvReceive:
begin
str := MSComm1.Input;
Memo1.Text :=Memo1.Text str;
SendMessage(Memo1.Handle, WM_VSCROLL, SB_BOTTOM, 0);
Memo2.Text :=Memo2.Text str;
SendMessage(Memo2.Handle, WM_VSCROLL, SB_BOTTOM, 0);
end;
end;
end;




procedure TForm1.Button4Click(Sender: TObject);
var
nPos:integer;
begin
Memo2.Text :='';
Edit1.Text :='';
MScomm1.Output :=Edit1.Text #13#10;
Edit1.Text :='';
Edit1.SetFocus();

application.processmessages;
sleep(200);

Memo2.Text :='';
Edit1.Text :='12';
MScomm1.Output :=Edit1.Text #13#10;
Edit1.Text :='';
Edit1.SetFocus();

application.processmessages;
sleep(200);

Memo2.Text :='';
Edit1.Text :='1';
MScomm1.Output :=Edit1.Text #13#10;
Edit1.Text :='';
Edit1.SetFocus();

application.processmessages;
sleep(200);

Memo2.Text :='';
Edit1.Text :='2';
MScomm1.Output :=Edit1.Text #13#10;
Edit1.Text :='';
Edit1.SetFocus();


application.processmessages;
sleep(200);

if MessageDlg('Exit now?',mtConfirmation,[mbYes, mbNo],0)=mrNo then
Label9.Caption :='LCD COLOR ERROR';

application.processmessages;
sleep(200);

Memo2.Text :='';
Edit1.Text :='3';
MScomm1.Output :=Edit1.Text #13#10;
Edit1.Text :='';
Edit1.SetFocus();

application.processmessages;
sleep(1200);

nPos := Pos('L',memo2.Text);
label9.caption :=inttostr(nPos);


end;

Memo2.Text :=''; <--已經把memo2.Text 清掉了
Edit1.Text :='3';
MScomm1.Output :=Edit1.Text #13#10;
Edit1.Text :='';
Edit1.SetFocus();

application.processmessages;
sleep(1200);

nPos := Pos('L',memo2.Text);
label9.caption :=inttostr(nPos);

memo2 是一個持續接受的過程，
只是在向設備發送命令前，將自己清空一下。
所以還請幫忙從其他角度分析，謝謝