簡單的MP3、WAV、MID播放器

新增5個TButton按鈕，Caption分別為：
&Open
>
■
&Back
&Next
再新增1個TProgressBar，1個TListBox，1個TMediaPlayer且屬性Visible = False。
1個TOpenDialog且屬性Filter = 所有音樂格式*.wav;*.mp3;*.mid
1個TTimer

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    ProgressBar1: TProgressBar;
    ListBox1: TListBox;
    MediaPlayer1: TMediaPlayer;
    Timer1: TTimer;
    OpenDialog1: TOpenDialog;
    procedure ListBox1Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    procedure PlayAudio;
    procedure NextTrack;
    procedure BackTrack;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  ss: String;
  PlayIndex: integer = 0;

implementation

{$R *.dfm}
procedure TForm1.PlayAudio;
begin
  try
    if ListBox1.Items.Count > 0 then //歌大於1首才可
    begin
      if ListBox1.ItemIndex = -1 then //未選擇就0 指第一首
        ListBox1.ItemIndex := 0;
      ss := ListBox1.Items.Strings[ListBox1.ItemIndex]; //取到檔名
      MediaPlayer1.FileName := ss;
      MediaPlayer1.Open;
      MediaPlayer1.Play;
    end;
  except;
  end;
end;

procedure TForm1.NextTrack;
begin
  try
    PlayIndex := ListBox1.ItemIndex;
    Inc(PlayIndex); //加1
    if PlayIndex = ListBox1.Items.Count then
      PlayIndex := 0; //跳到第一首
    ListBox1.ItemIndex := PlayIndex;

    ss := ListBox1.Items.Strings[PlayIndex];
    MediaPlayer1.FileName := ss;
    MediaPlayer1.Open;
    if MediaPlayer1.FileName = '' then
      PlayAudio
    else
      MediaPlayer1.Resume;
  except;
  end;
end;

procedure TForm1.BackTrack;
begin
  try
    PlayIndex := ListBox1.ItemIndex;
    Dec(PlayIndex); //減1
    if PlayIndex < filename =" ''" filename =" ''" caption =" '">' then
    begin
      MediaPlayer1.Resume;
      button2.caption:='';
    end else
    begin
      MediaPlayer1.Pause;
      button2.caption:='>';
    end;
  except;
  end;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  try
    BackTrack
  except
  end;
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
  try
    NextTrack
  except
  end;
end;

procedure TForm1.ListBox1Click(Sender: TObject); //連點兩下
begin
  PlayAudio;
  button2.caption:='';
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  if MediaPlayer1.FileName <> '' then
    try
      ProgressBar1.Max := MediaPlayer1.Length; //MediaPlayer1.Length音樂長度
      ProgressBar1.Position := MediaPlayer1.Position; //MediaPlayer1.Position播放位置
      ProgressBar1.Update;
      MediaPlayer1.Update;
      if MediaPlayer1.Position >= MediaPlayer1.Length then
        NextTrack;
    except;
    end;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  MediaPlayer1.stop; //停止播放
  MediaPlayer1.FileName := ''; //名稱為''是為了跑PlayAudio
  button2.caption:='>'; //按鈕圖示變
  ProgressBar1.Position := 0; //手控狀態bar
end;

end.