Question

我正在使用一个Delphi XE2项目来显示滚动文本（更好的“Marquee Text”）。在我的项目中，我有Timer1，Timer2，Button1，Button2，Label1和Label2。我的目标是在使用Label1 Button1.Click后Timer1上显示一些左滚动文字，使用Label2 Button1.Click后Timer2上的一些右滚动文字

我已经定义了以下代码：

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Button1: TButton;
    Button2: TButton;
    Timer1: TTimer;
    Timer2: TTimer;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure Timer2Timer(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  Timer1.Enabled := true;
  Timer2.Enabled := true;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Timer1.Enabled := false;
  Timer2.Enabled := false;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer1.Interval := 100;
  Timer2.Interval := 100;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
const
{$WRITEABLECONST ON}
  ScrollingText : string = 'This is left scrolling text ';
{$WRITEABLECONST OFF}
var
  ScrollPosition: Integer;
begin
  Label1.Caption := ScrollingText;
  for ScrollPosition := 1 to (Length(ScrollingText) - 1) do
    begin
      ScrollingText[ScrollPosition] := Label1.Caption[ScrollPosition + 1];
      ScrollingText[Length(ScrollingText)] := Label1.Caption[1];
     end;
end;

procedure TForm1.Timer2Timer(Sender: TObject);
const
{$WRITEABLECONST ON}
  ScrollingText : string = 'This is right scrolling text ';
{$WRITEABLECONST OFF}
var
  ScrollPosition: Integer;
begin
  Label2.Caption := ScrollingText;
  for ScrollPosition := (Length(ScrollingText) - 1) to 1 do
    begin
      ScrollingText[ScrollPosition] := Label2.Caption[ScrollPosition - 1];
      ScrollingText[Length(ScrollingText)] := Label2.Caption[1];
    end;
end;

end.

我的问题是Left Scrolling正在使用Timer1，但Right Scrolling没有使用Timer2发生。

Answer 1

for中的Timer2Timer循环应该向下而不是向上运行：

procedure TForm1.Timer2Timer(Sender: TObject);
const
{$WRITEABLECONST ON}
  ScrollingText : string = 'This is right scrolling text ';
{$WRITEABLECONST OFF}
var
  ScrollPosition: Integer;
begin
  Label2.Caption := ScrollingText;
  for ScrollPosition := (Length(ScrollingText) - 1) downto 2 do
    begin
      ScrollingText[ScrollPosition] := Label2.Caption[ScrollPosition - 1];
      ScrollingText[1] := Label2.Caption[Length(ScrollingText) - 1];
    end;
end;

但我建议不要使用可写const，也不要使用for循环：

procedure TForm1.FormCreate(Sender: TObject);
begin
  ...
  Label2.Caption := 'This is right scrolling text ';
end;

procedure TForm1.Timer2Timer(Sender: TObject);
var
  S: String;
begin
  S := Label2.Caption;
  S := S[Length(S)] + Copy(S, 1, Length(S) - 1);
  Label2.Caption := S;
end;

右滚动文字

1 个答案: