Delphi 利用 IdHTTP 进行多线程下载
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MARK - 基于早期 Delphi 7 + Indy V9.00.10 的 Sample。
下载工具经常会多线程帮助用户下载，Delphi 实现的基本原理 MARK：
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ComCtrls, StdCtrls, IdComponent, IdTCPConnection, IdTCPClient,
IdHTTP, IdBaseComponent, IdAntiFreezeBase, IdAntiFreeze,
IdThreadComponent, IdFTP;
type
TThread1 = class(TThread)
private
fCount, tstart, tlast: integer;
tURL, tFile, temFileName: string;
tResume: Boolean;
tStream: TFileStream;
protected
procedure Execute; override;
public
constructor create1(aURL, aFile, fileName: string; bResume: Boolean; Count,
start, last: integer);
procedure DownLodeFile(); //下载文件
end;
type
TForm1 = class(TForm)
IdAntiFreeze1: TIdAntiFreeze;
IdHTTP1: TIdHTTP;
Button1: TButton;
ProgressBar1: TProgressBar;
IdThreadComponent1: TIdThreadComponent;
Label1: TLabel;
Label2: TLabel;
Button2: TButton;
Button3: TButton;
ListBox1: TListBox;
Edit1: TEdit;
Edit2: TEdit;
Label3: TLabel;
Label4: TLabel;
procedure Button1Click(Sender: TObject);
procedure IdHTTP1WorkBegin(Sender: TObject; AWorkMode: TWorkMode;
const AWorkCountMax: Integer);
procedure IdHTTP1Work(Sender: TObject; AWorkMode: TWorkMode;
const AWorkCount: Integer);
procedure Button2Click(Sender: TObject);
procedure IdHTTP1Status(ASender: TObject; const AStatus: TIdStatus;
const AStatusText: string);
procedure Button3Click(Sender: TObject);
private
public
nn, aFileSize, avg: integer;
MyThread: array[1..10] of TThread;
procedure GetThread();
procedure AddFile();
function GetURLFileName(aURL: string): string;
function GetFileSize(aURL: string): integer;
end;
var
Form1: TForm1;
implementation
var
AbortTransfer: Boolean;
aURL, aFile: string;
tcount: integer; //检查文件是否全部下载完毕
{$R *.dfm}
//get FileName
function TForm1.GetURLFileName(aURL: string): string;
var
i: integer;
s: string;
begin //返回下载地址的文件名
s := aURL;
i := Pos('/', s);
while i <> 0 do //去掉"/"前面的内容剩下的就是文件名了
begin
Delete(s, 1, i);
i := Pos('/', s);
end;
Result := s;
end;
//get FileSize
function TForm1.GetFileSize(aURL: string): integer;
var
FileSize: integer;
begin
IdHTTP1.Head(aURL);
FileSize := IdHTTP1.Response.ContentLength;
IdHTTP1.Disconnect;
Result := FileSize;
end;
//执行下载
procedure TForm1.Button1Click(Sender: TObject);
var
j: integer;
begin
tcount := 0;
Showmessage('OK!主线程在执行，获得文件名并显示在Edit2中');
aURL := Edit1.Text; //下载地址
aFile := GetURLFileName(Edit1.Text); //得到文件名
nn := StrToInt(Edit2.Text); //线程数
j := 1;
aFileSize := GetFileSize(aURL);
avg := trunc(aFileSize / nn);
begin
try
GetThread();
while j <= nn do
begin
MyThread[j].Resume; //唤醒线程
j := j + 1;
end;
except
Showmessage('创建线程失败!');
Exit;
end;
end;
end;
//开始下载前,将ProgressBar1的最大值设置为需要接收的数据大小.
procedure TForm1.IdHTTP1WorkBegin(Sender: TObject; AWorkMode: TWorkMode;
const AWorkCountMax: Integer);
begin
AbortTransfer := False;
ProgressBar1.Max := AWorkCountMax;
ProgressBar1.Min := 0;
ProgressBar1.Position := 0;
end;
//接收数据的时候,进度将在ProgressBar1显示出来.
procedure TForm1.IdHTTP1Work(Sender: TObject; AWorkMode: TWorkMode;
const AWorkCount: Integer);
begin
if AbortTransfer then
begin
IdHTTP1.Disconnect; //中断下载
end;
ProgressBar1.Position := AWorkCount;
//ProgressBar1.Position:=ProgressBar1.Position+AWorkCount; //*******显示速度极快
Application.ProcessMessages;
//***********************************这样使用不知道对不对
end;
//中断下载
procedure TForm1.Button2Click(Sender: TObject);
begin
AbortTransfer := True;
IdHTTP1.Disconnect;
end;
//状态显示
procedure TForm1.IdHTTP1Status(ASender: TObject; const AStatus: TIdStatus;
const AStatusText: string);
begin
ListBox1.ItemIndex := ListBox1.Items.Add(AStatusText);
end;
//退出程序
procedure TForm1.Button3Click(Sender: TObject);
begin
application.Terminate;
end;
//循环产生线程
procedure TForm1.GetThread();
var
i: integer;
start: array[1..100] of integer;
last: array[1..100] of integer; //改用了数组，也可不用
fileName: string;
begin
i := 1;
while i <= nn do
begin
start[i] := avg * (i - 1);
last[i] := avg * i -1; //这里原先是last:=avg*i;
if i = nn then
begin
last[i] := avg*i + aFileSize-avg*nn; //这里原先是aFileSize
end;
fileName := aFile + IntToStr(i);
MyThread[i] := TThread1.create1(aURL, aFile, fileName, false, i, start[i],
last[i]);
i := i + 1;
end;
end;
procedure TForm1.AddFile(); //合并文件
var
mStream1, mStream2: TMemoryStream;
i: integer;
begin
i := 1;
mStream1 := TMemoryStream.Create;
mStream2 := TMemoryStream.Create;
mStream1.loadfromfile('设备工程进度管理前期规划.doc' + '1');
while i < nn do
begin
mStream2.loadfromfile('设备工程进度管理前期规划.doc' + IntToStr(i + 1));
mStream1.seek(mStream1.size, soFromBeginning);
mStream1.copyfrom(mStream2, mStream2.size);
mStream2.clear;
i := i + 1;
end;
mStream2.free;
mStream1.SaveToFile('设备工程进度管理前期规划.doc');
mStream1.free;
//删除临时文件
i:=1;
while i <= nn do
begin
deletefile('设备工程进度管理前期规划.doc' + IntToStr(i));
i := i + 1;
end;
Form1.ListBox1.ItemIndex := Form1.ListBox1.Items.Add('下在成功');
end;
//构造函数
constructor TThread1.create1(aURL, aFile, fileName: string; bResume: Boolean;
Count, start, last: integer);
begin
inherited create(true);
FreeOnTerminate := true;
tURL := aURL;
tFile := aFile;
fCount := Count;
tResume := bResume;
tstart := start;
tlast := last;
temFileName := fileName;
end;
//下载文件函数
procedure TThread1.DownLodeFile();
var
temhttp: TIdHTTP;
begin
temhttp := TIdHTTP.Create(nil);
temhttp.onWorkBegin := Form1.IdHTTP1WorkBegin;
temhttp.onwork := Form1.IdHTTP1work;
temhttp.onStatus := Form1.IdHTTP1Status;
Form1.IdAntiFreeze1.OnlyWhenIdle := False; //设置使程序有反应.
if FileExists(temFileName) then //如果文件已经存在
tStream := TFileStream.Create(temFileName, fmOpenWrite)
else
tStream := TFileStream.Create(temFileName, fmCreate);
if tResume then //续传方式
begin
exit;
end
else //覆盖或新建方式
begin
temhttp.Request.ContentRangeStart := tstart;
temhttp.Request.ContentRangeEnd := tlast;
end;
try
temhttp.Get(tURL, tStream); //开始下载
Form1.ListBox1.ItemIndex := Form1.ListBox1.Items.Add(temFileName +
'download');
finally
//tStream.Free;
freeandnil(tstream);
temhttp.Disconnect;
end;
end;
procedure TThread1.Execute;
begin
if Form1.Edit1.Text <> '' then
//synchronize(DownLodeFile)
DownLodeFile
else
exit;
inc(tcount);
if tcount = Form1.nn then //当tcount=nn时代表全部下载成功
begin
//Showmessage('全部下载成功!');
Form1.ListBox1.ItemIndex := Form1.ListBox1.Items.Add('正在合并删除临时文件');
Form1.AddFile;
end;
end;
end.
Delphi 自带的控件的 INDY 组件 + TIdAntiFreeze 控件 + TProgressBar 用于显示下载进度，用 TButton 开始执行我们的测试：
procedure TForm1.Button1Click(Sender: TObject);//点击按钮的时候开始下载我们的文件
var
MyStream:TMemoryStream;
begin
IdAntiFreeze1.OnlyWhenIdle:=False;//设置使程序有反应.
MyStream:=TMemoryStream.Create;
try
IdHTTP1.Get('https://commandnotfound.cn/download/Mp3ToExe.zip',MyStream);//下载我站点的一个ZIP文件
except//INDY控件一般要使用这种try..except结构.
Showmessage('网络出错!');
MyStream.Free;
Exit;
end;
MyStream.SaveToFile('c:\Mp3ToExe.zip');
MyStream.Free;
Showmessage('OK');
end;
procedure TForm1.IdHTTP1WorkBegin(Sender: TObject; AWorkMode: TWorkMode;
const AWorkCountMax: Integer);//开始下载前,将ProgressBar1的最大值设置为需要接收的数据大小.
begin
ProgressBar1.Max:=AWorkCountMax;
ProgressBar1.Min:=0;
ProgressBar1.Position:=0;
end;
procedure TForm1.IdHTTP1Work(Sender: TObject; AWorkMode: TWorkMode;
const AWorkCount: Integer);//接收数据的时候,进度将在ProgressBar1显示出来.
begin
ProgressBar1.Position:=ProgressBar1.Position+AWorkCount;
end;
IdHTTP1 的 Get 还有一种形式就是获取字符串，可以改写成：
procedure TForm1.Button1Click(Sender: TObject);
var
MyStr:String;
begin
IdAntiFreeze1.OnlyWhenIdle:=False;//设置使程序有反应.
try
MyStr:=IdHTTP1.Get('https://commandnotfound.cn/default.htm');
except
Showmessage('网络出错!');
Exit;
end;
Showmessage(MyStr);
end;