求高手指点,急!22号之前急要!

Question

题目是:编写程序在列表框里传送数据
 ListBox1: TListBox;
    ListBox2: TListBox;
    Label1: TLabel;
    Label2: TLabel;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
procedure TForm1.FormCreate(Sender: TObject);
begin
listbox1.Selected[0]:=true;
end;procedure TForm1.Button1Click(Sender: TObject);
begin
if  listbox1.Count>0 then
  begin
    listbox2.Items.Add(listbox1.Items[listbox1.itemindex]);
    listbox1.Items.delete(listbox1.itemindex);
    listbox1.Selected[0]:=true;
    listbox2.Selected[0]:=true;
  end;
if  listbox1.Count<=0 then
showmessage('错误');
end;procedure TForm1.Button2Click(Sender: TObject);
var
i:integer;
begin
 for i:=1 to 5 do
   begin
     listbox2.Items.Add(listbox1.Items[i]);
     listbox1.Selected[0]:=true;
   end;
end;procedure TForm1.Button5Click(Sender: TObject);
begin
close;
end;end.
问问在删除一项和删除所有项的代码是如何的,还有为什么添加所有项时会弹出错误.

Answer 1

procedure   TForm1.Button2Click(Sender:   TObject); 
var 
i:integer; 
begin 
  for   i:=1   to   5   do 
      begin 
          listbox2.Items.Add(listbox1.Items[i]); 
          listbox1.Selected[0]:=true;   //去掉這行試試
      end; 
end; 

Answer 2

procedure   TForm1.FormCreate(Sender:   TObject);
begin
listbox1.Selected[0]:=true;
//代码隐患:如果ListBox1.Count=0,将报错.可以用 listBox1.SetFocus;
end;procedure   TForm1.Button1Click(Sender:   TObject);
begin
if listbox1.Count> 0   then
    begin
        //隐患: 如果ListBox1.ItemIndex<0即没选中,listbox1.Items[listbox1.itemindex]将出错.
        listbox2.Items.Add(listbox1.Items[listbox1.itemindex]);
        //隐患,同上
        listbox1.Items.delete(listbox1.itemindex);
        //隐患: 如果ListBox1.Count=0,将出错.
        listbox1.Selected[0]:=true;
        listbox2.Selected[0]:=true;
    end;
if     listbox1.Count <=0   then
showmessage('错误');
end;procedure   TForm1.Button2Click(Sender:   TObject);
var
i:integer;
begin
  for   i:=1   to   5   do
      begin
          listbox2.Items.Add(listbox1.Items[i]);  //如果listbox1的总行数小于6,将出错
          listbox1.Selected[0]:=true;             //=0行,出错.
      end;
end;你的语言基础还有逻辑思维非常不严谨.