用多媒體庫 Bass.dll 播放 mp3 [4] - 顯示與設置播放進度

本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, ExtCtrls;
type
　TForm1 = class(TForm)
　　OpenDialog1: TOpenDialog;
　　Timer1: TTimer;
　　Button1: TButton;
　　Button2: TButton;
　　Button3: TButton;
　　ScrollBar1: TScrollBar;
　　procedure FormCreate(Sender: TObject);
　　procedure Button1Click(Sender: TObject);
　　procedure Button2Click(Sender: TObject);
　　procedure Button3Click(Sender: TObject);
　　procedure Timer1Timer(Sender: TObject);
　　procedure ScrollBar1Scroll(Sender: TObject; ScrollCode: TScrollCode;
　　　var ScrollPos: Integer);
　　procedure FormDestroy(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses Bass;
var
　hs: HSTREAM;　{流句柄}
　time: Double; {樂曲總時間}
procedure TForm1.FormCreate(Sender: TObject);
begin
　Timer1.Interval := 100;
　Timer1.Enabled := False;
　ScrollBar1.Enabled := False;
　if HiWord(BASS_GetVersion) <> BASSVERSION then
　　MessageBox(0, '"Bass.dll" 文件版本不合適! ', nil, MB_ICONERROR);
　if not BASS_Init(-1, 44100, 0, 0, nil) then
　　ShowMessage('初始化錯誤');
end;
{打開}
procedure TForm1.Button1Click(Sender: TObject);
var
　Mp3Path: AnsiString;
begin
　BASS_StreamFree(hs);
　Timer1.Enabled := False;
　ScrollBar1.Enabled := False;
　OpenDialog1.Filter := 'Mp3 文件(*.mp3)|*.mp3|Wav 文件(*.wav)|*wav';
　if OpenDialog1.Execute then
　　Mp3Path := AnsiString(OpenDialog1.FileName);
　hs := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, 0);
　if hs < BASS_ERROR_ENDED then
　　Text := '打開失敗'
　else begin
　　Text := string(Mp3Path);
　　time := BASS_ChannelBytes2Seconds(hs, BASS_ChannelGetLength(hs, BASS_POS_BYTE)); {總秒數}
　　ScrollBar1.Max := Trunc(time * 1000);
　　ScrollBar1.Enabled := True;
　end;
end;
{播放}
procedure TForm1.Button2Click(Sender: TObject);
begin
　BASS_ChannelPlay(hs, False);
　Timer1.Enabled := True;
end;
{暫停}
procedure TForm1.Button3Click(Sender: TObject);
begin
　Timer1.Enabled := False;
　BASS_ChannelPause(hs);
end;
{播放時需要的顯示}
procedure TForm1.Timer1Timer(Sender: TObject);
var
　s: Double; {當前秒數}
begin
　s := BASS_ChannelBytes2Seconds(hs, BASS_ChannelGetPosition(hs, BASS_POS_BYTE));
　Text := Concat(FloatToStr(time), ' / ', FloatToStr(s));
　ScrollBar1.Position := Trunc(s * 1000);
end;
{調整播放位置}
procedure TForm1.ScrollBar1Scroll(Sender: TObject; ScrollCode: TScrollCode;
　var ScrollPos: Integer);
var
　Position: Int64;
begin
　Button3.Click;
　Position := BASS_ChannelSeconds2Bytes(hs, ScrollPos / 1000);
　BASS_ChannelSetPosition(hs, Position, BASS_POS_BYTE);
　Text := Concat(FloatToStr(time), ' / ', FloatToStr(Position / 1000));
　Timer1Timer(nil);
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
　BASS_Free;
end;
end.窗體文件:object Form1: TForm1
　Left = 205
　Top = 107
　Caption = 'Form1'
　ClIEntHeight = 88
　ClIEntWidth = 393
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesigned
　OnCreate = FormCreate
　OnDestroy = FormDestroy
　PixelsPerInch = 96
　TextHeight = 13
　object Button1: TButton
　　Left = 65
　　Top = 17
　　Width = 75
　　Height = 25
　　Caption = #25171#24320
　　TabOrder = 0
　　OnClick = Button1Click
　end
　object Button2: TButton
　　Left = 161
　　Top = 17
　　Width = 75
　　Height = 25
　　Caption = #25773#25918
　　TabOrder = 1
　　OnClick = Button2Click
　end
　object Button3: TButton
　　Left = 257
　　Top = 17
　　Width = 75
　　Height = 25
　　Caption = #26242#20572
　　TabOrder = 2
　　OnClick = Button3Click
　end
　object ScrollBar1: TScrollBar
　　Left = 8
　　Top = 56
　　Width = 377
　　Height = 17
　　PageSize = 0
　　TabOrder = 3
　　OnScroll = ScrollBar1Scroll
　end
　object OpenDialog1: TOpenDialog
　　Left = 40
　　Top = 40
　end
　object Timer1: TTimer
　　OnTimer = Timer1Timer
　　Left = 80
　　Top = 48
　end