如何使用 TIdHTTP 一次下载多个文件

Question

我目前正在使用来自 Indy 的 TIdHTTP 和我的 Embarcadero C++Builder 10.1 Berlin。我已经阅读了一些关于如何使 TIdHTTP 成为多线程的在线教程，但主要问题是我已经在一个线程中测试了这个组件。

这就是它的工作原理。我创建了一个线程对象，并创建了一个函数来在该线程中下载文件，显然该线程工作正常并且文件已下载到我的磁盘。但是，当我为文件下载创建额外的线程时，第一个线程停止了。我不想这样，我希望两个文件同时继续下载（不暂停第一个线程），就像在 IDM（Internet 下载管理器）中一样。

线程 class 就像下面的代码：

class TIdHTTPThread : public TThread
{
protected:
        void __fastcall Execute();
        void __fastcall PutDownloadedFile();
    public:
        __fastcall TIdHTTPThread(bool CreateSuspended);
        void __fastcall IdHTTPBeginWork(TObject *ASender, TWorkMode AWorkMode,
              __int64 AWorkCountMax);
        void __fastcall IdHTTPWork(TObject *ASender, TWorkMode AWorkMode,
          __int64 AWorkCount);
        void __fastcall IdHTTPEndWork(TObject *ASender, TWorkMode AWorkMode);
        void __fastcall DownloadFile(UnicodeString AFileURL, UnicodeString AFileDest);
        void __fastcall CreateQueue(TWinControl* wcParent, TAlign alAlign);
    private:
        TIdHTTP* IdHTTP;
        TMemoryStream* msMemoryStream;
        UnicodeString uFileURL;
        UnicodeString uFileDest;
        int iDownProgress;
        int iFileSize;
        int iMaxProgress;
        int iDownSpeed;
        TWinControl* wcParent;
        TIFDQueue *ifdQueue;
};

请不要理会class中的额外属性和方法，我只想实现我的问题。

CPP 文件：

void __fastcall TIdHTTPThread::CreateQueue(TWinControl* wcParent, TAlign alAlign)
{
    this->wcParent = wcParent;
    ifdQueue = new TIFDQueue(this->wcParent, alAlign);
}

void __fastcall TIdHTTPThread::IdHTTPBeginWork(TObject *ASender, TWorkMode AWorkMode,
              __int64 AWorkCountMax)
{
    this->iFileSize     = AWorkCountMax;
    this->iMaxProgress  = AWorkCountMax;
    ifdQueue->SetFileSize(this->iFileSize);
    ifdQueue->SetMaxProgress(this->iMaxProgress);
    ifdQueue->SetFileURL(this->uFileURL);
    ifdQueue->SetFilePath(this->uFileDest);
    ifdQueue->OnBeginUpdate();
}

void __fastcall TIdHTTPThread::IdHTTPWork(TObject *ASender, TWorkMode AWorkMode,
          __int64 AWorkCount)
{
    this->iDownProgress = AWorkCount;
    this->iDownSpeed    = AWorkCount / 1024;
    ifdQueue->SetDownProgress(this->iDownProgress);
    ifdQueue->SetDownSpeed(this->iDownSpeed);
    ifdQueue->OnWorkUpdate();
}

void __fastcall TIdHTTPThread::IdHTTPEndWork(TObject *ASender, TWorkMode AWorkMode)
{
    ifdQueue->OnEndUpdate();
    this->Terminate();
}
//**//

void __fastcall TIdHTTPThread::DownloadFile(UnicodeString AFileURL, UnicodeString AFileDest)
{
    this->uFileURL  = AFileURL;
    this->uFileDest = AFileDest;
}

void __fastcall TIdHTTPThread::PutDownloadedFile()
{
    try {
        this->msMemoryStream = new TMemoryStream;
        this->IdHTTP                = new TIdHTTP(NULL);
        this->IdHTTP->OnWorkBegin   = this->IdHTTPBeginWork;
        this->IdHTTP->OnWork        = this->IdHTTPWork;
        this->IdHTTP->OnWorkEnd     = this->IdHTTPEndWork;
        this->IdHTTP->ConnectTimeout = 20000;
        this->IdHTTP->ReadTimeout   = 60000;
        this->IdHTTP->Get(this->uFileURL, this->msMemoryStream);
        this->msMemoryStream->SaveToFile(this->uFileDest);
    } __finally {
        delete this->msMemoryStream;
        delete this->IdHTTP;
    }
}

__fastcall TIdHTTPThread::TIdHTTPThread(bool CreateSuspended)
    : TThread(CreateSuspended)
{

}
//---------------------------------------------------------------------------
void __fastcall TIdHTTPThread::Execute()
{
    //---- Place thread code here ----
    FreeOnTerminate = true;
    Synchronize(&this->PutDownloadedFile);
}
//---------------------------------------------------------------------------

更新：

void __fastcall TIdHTTPThread::PutDownloadedFile()
{
    try {
        this->CookieManager = new TIdCookieManager(NULL);
        this->SSLIOHandlerSocket = new TIdSSLIOHandlerSocketOpenSSL(NULL);
        this->msMemoryStream = new TMemoryStream;
        // Configure SSL IOHandler
        this->SSLIOHandlerSocket->SSLOptions->Method = sslvSSLv23;
        this->SSLIOHandlerSocket->SSLOptions->SSLVersions = TIdSSLVersions() << sslvTLSv1_2 << sslvTLSv1_1 << sslvTLSv1;
        // Setup HTTP
        this->IdHTTP                  = new TIdHTTP(NULL);
        this->ifdQueue->StopDownload(this->IdHTTP);  // Function To stop download When Fired (doesn't fire imidiatly)
        this->IdHTTP->OnWorkBegin     = this->IdHTTPBeginWork;
        this->IdHTTP->OnWork          = this->IdHTTPWork;
        this->IdHTTP->OnWorkEnd       = this->IdHTTPEndWork;
        this->IdHTTP->OnRedirect      = this->IdHTTPRedirect;
        this->IdHTTP->HandleRedirects = true;
        this->IdHTTP->AllowCookies    = true;
        this->IdHTTP->CookieManager   = this->CookieManager;
        this->IdHTTP->IOHandler       = this->SSLIOHandlerSocket;
        this->IdHTTP->Get(this->uFileURL, this->msMemoryStream);
        if ( this->msMemoryStream->Size >= this->IdHTTP->Response->ContentLength ) {
            this->msMemoryStream->SaveToFile(this->uFileName);
        }
    } __finally {
        delete this->msMemoryStream;
        delete this->CookieManager;
        delete this->SSLIOHandlerSocket;
        delete this->IdHTTP;
    }
}

Answer 1

问题是您的线程的 Execute() 方法正在 Synchronize() 调用中完成其所有工作，因此它的所有工作实际上都在主 UI 线程中完成，从而序列化您的下载并破坏使用工作线程的全部意义。

不要用 Synchronize() 调用 PutDownloadedFile() 本身。在更新 UI 控件时，您需要更改个人 TIdHTTP 状态事件以使用 Synchronize()（或 Queue()）。

如何使用 TIdHTTP 一次下载多个文件

How to download multiple files at once with TIdHTTP

multithreading

indy

c++builder

idhttp