用多媒體庫 Bass.dll 播放 mp3 [10] – 使用回呼函數

本例:

代碼檔案:

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls, ExtCtrls, ComCtrls;type  TForm1 = class(TForm)    OpenDialog1: TOpenDialog;    TrackBar1: TTrackBar;    Timer1: TTimer;    Button1: TButton;    Button2: TButton;    Button3: TButton;    procedure FormCreate(Sender: TObject);    procedure Button1Click(Sender: TObject);    procedure Button2Click(Sender: TObject);    procedure Button3Click(Sender: TObject);    procedure FormDestroy(Sender: TObject);    procedure Timer1Timer(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}uses Bass;var  hs: HSTREAM;  {流控制代碼}{回呼函數: MySync1; 儘管沒有用到其中的任何參數, 但也要按指定的參數格式來寫}procedure MySync1(handle: HSYNC; channel, data, user: DWORD); stdcall;begin  Form1.Text := '開始播放了';end;{回呼函數: MySync2}{參數1: 是回調控制代碼, 它可有 BASS_ChannelSetSync 返回, 並可用 BASS_ChannelRemoveSync 刪除}{參數2: 流控制代碼}{參數3: 不知道}{參數4: 是 BASS_ChannelSetSync 指定的使用者資料}procedure MySync2(handle: HSYNC; channel, data, user: DWORD); stdcall;begin  Form1.Text := '已過中點';  {假如播放至此(中間點)就從頭反覆, 可以這樣:}  //BASS_ChannelPlay(channel, True);end;{回呼函數: MySync3; 儘管沒有用到其中的任何參數, 但也必須按要求指定}procedure MySync3(handle: HSYNC; channel, data, user: DWORD); stdcall;begin  Form1.Text := '播放完畢';end;{初始化}procedure TForm1.FormCreate(Sender: TObject);begin  TrackBar1.Height := 23;  Timer1.Enabled := False;  Timer1.Interval := 100;  if HiWord(BASS_GetVersion)  BASSVERSION then    MessageBox(0, '"Bass.dll" 檔案版本不合適! ', nil, MB_ICONERROR);  if not BASS_Init(-1, 44100, 0, 0, nil) then ShowMessage('初始化錯誤');end;{開啟}procedure TForm1.Button1Click(Sender: TObject);var  Mp3Path: AnsiString;  Mp3Len: Cardinal;begin  BASS_StreamFree(hs);  Timer1.Enabled := False;  OpenDialog1.Filter := 'Mp3 檔案(*.mp3)|*.mp3|Wav 檔案(*.wav)|*wav';  if OpenDialog1.Execute then    Mp3Path := AnsiString(OpenDialog1.FileName);  hs := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, 0);  if hs 

表單檔案:

object Form1: TForm1  Left = 222  Top = 114  Caption = 'Form1'  ClientHeight = 84  ClientWidth = 254  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 = 8    Top = 18    Width = 75    Height = 25    Caption = #25171#24320    TabOrder = 0    OnClick = Button1Click  end  object Button2: TButton    Left = 89    Top = 18    Width = 75    Height = 25    Caption = #25773#25918    TabOrder = 1    OnClick = Button2Click  end  object Button3: TButton    Left = 170    Top = 18    Width = 75    Height = 25    Caption = #26242#20572    TabOrder = 2    OnClick = Button3Click  end  object TrackBar1: TTrackBar    Left = 1    Top = 53    Width = 250    Height = 28    TabOrder = 3  end  object OpenDialog1: TOpenDialog    Left = 72    Top = 32  end  object Timer1: TTimer    OnTimer = Timer1Timer    Left = 152    Top = 32  endend