用ListBox 選擇 Item (包括全選、反向選擇)

新增
5個按鈕TButton
1個TListBox, MultiSelect=true
1個TMemo

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    Memo1: TMemo;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  ListBox1.SelectAll; //全選
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  i: integer;
begin
  for i:=0 to ListBox1.Count-1 do
  begin
    ListBox1.Selected[i]:=(not ListBox1.Selected[i]);
  end;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ListBox1.ClearSelection;
end;

procedure TForm1.Button4Click(Sender: TObject);
var
  i: integer;
begin
  Memo1.Clear; // 先清除Memo1的內容
  Memo1.Lines.Add('你這次選了以下的選項');
  for i:=0 to ListBox1.Count-1 do
    if (ListBox1.Selected[i]) then
      Memo1.Lines.Add(ListBox1.Items.Strings[i]);

  if (Memo1.Lines.Count=1) then // 沒有選擇任何一個
  begin
    Memo1.Clear;
    Memo1.Lines.Add('你沒有選擇任何一個');
  end;
end;

procedure TForm1.Button5Click(Sender: TObject);
var
  i: integer;
begin
  if (ListBox1.SelCount=0) then exit; // 沒有選擇任何一個
  for i:=0 to ListBox1.Count-1 do // 找出點選了哪個
    if ListBox1.Selected[i] then
      Memo1.Lines.Add(ListBox1.Items.Strings[i]); // 加到右邊

  ListBox1.DeleteSelected; // 刪除左邊
end;
end.