Delphi实现文件下载并且显示下载进度

Delphi实现文件下载并且显示下载进度 需要用到的API函数名字为 URLDownloadToFile 此函数在UrlMon单元中的声明如下: const UrlMonLib = 'URLMON.DLL'; function URLDownloadToFile; external UrlMonLib name 'URLDownloadToFileA'; function URLDownloadToFile(Caller: IUnknown; URL: PChar; FileName: PChar; Reserved: DWORD; StatusCB: IBindStatusCallback): HResult; stdcall; 关于其中的参数用意大家可以直接访问 来得到解释( 下面我们将获取该函数的下载进度 实现 IBindStatusCallback 接口即可， 该接口在 UrlMon单元中的具体声明: IBindStatusCallback = interface ['{79eac9c1-baf9-11ce-8c82-00aa004ba90b}'] function OnStartBinding(dwReserved: DWORD; pib: IBinding): HResult; stdcall; function GetPriority(out nPriority): HResult; stdcall; function OnLowResource(reserved: DWORD): HResult; stdcall; function OnProgress(ulProgress, ulProgressMax, ulStatusCode: ULONG; szStatusText: LPCWSTR): HResult; stdcall; function OnStopBinding(hresult: HResult; szError: LPCWSTR): HResult; stdcall; function GetBindInfo(out grfBINDF: DWORD; var bindinfo: TBindInfo): HResult; stdcall; function OnDataAvailable(grfBSCF: DWORD; dwSize: DWORD; formatetc: PFormatEtc; stgmed: PStgMedium): HResult; stdcall; function OnObjectAvailable(const iid: TGUID; punk: IUnknown): HResult; stdcall; end; 接下来我们所要完成的任务就是写一个类来实现 IBindStatusCallback 接口，请看下面 unit BindStatusCallback; interface uses SysUtils, Windows, UrlMon, ActiveX; type TNotifyDownloading = procedure (FileName: PChar; ulProgress, ulProgressMax, ulStatusCode: ULONG; szStatusText: LPCWSTR) of object; TBindStatusCallback = class(TObject, IBindStatusCallback) protected FRefCount: Integer; FNotifyDownloading: TNotifyDownloading; function QueryInterface(const IID: TGUID; out Obj): Integer; stdcall; function _AddRef: Integer; stdcall; function _Release: Integer; stdcall; public FileName: string; property OnDownloading: TNotifyDownloading read FNotifyDownloading write FNotifyDownloading; function OnStartBinding(dwReserved: DWORD; pib: IBinding): HResult; stdcall; function GetPriority(out nPriority): HResult; stdcall; function OnLowResource(reserved: DWORD): HResult; stdcall; function OnProgress(ulProgress, ulProgressMax, ulStatusCode: ULONG; szStatusText: LPCWSTR): HResult; stdcall; function OnStopBinding(hresult: HResult; szError: LPCWSTR): HResult; stdcall; function GetBindInfo(out grfBINDF: DWORD; var bindinfo: TBindInfo): HResult; stdcall; function OnDataAvailable(grfBSCF: DWORD; dwSize: DWORD; formatetc: PFormatEtc; stgmed: PStgMedium): HResult; stdcall; function OnObjectAvailable(const iid: TGUID; punk: IUnkno end; implementation { TBindStatusCallback } function TBindStatusCallback.QueryInterface(const IID: TGUID; out Obj): Integer; begin if GetInterface(IID, Obj) then Result := S_OK else Result := E_NOINTERFACE; end; function TBindStatusCallback._AddRef: Integer; begin Inc(FRefCount); Result := FRefCount; end; function TBindStatusCallback._Release: Integer; begin Dec(FRefCount); Result := FRefCount; end; function TBindStatusCallback.GetBindInfo(out grfBINDF: DWORD; var bindinfo: TBindInfo): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.GetPriority(out nPriority): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.OnDataAvailable(grfBSCF, dwSize: DWORD; formatetc: PFormatEtc; stgmed: PStgMedium): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.OnLowResource(reserved: DWORD): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.OnObjectAvailable(const iid: TGUID; punk: IUnknown): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.OnStartBinding(dwReserved: DWORD; pib: IBinding): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.OnStopBinding(hresult: HResult; szError: LPCWSTR): HResult; begin Result := E_NOTIMPL; end; function TBindStatusCallback.OnProgress(ulProgress, ulProgressMax, ulStatusCode: ULONG; szStatusText: LPCWSTR): HResult; begin if (Assigned(FNotifyDownloading)) then FNotifyDownloading(Pchar(FileName), ulProgress, ulProgressMax, ulStatusCode, szStatusText); Result := S_OK; end; end. 大家可能注意到了怎么多了个 FNotifyDownloading 事件, 没错， 这个事实是用来实现进 度回调的(只需要您的事件类型声明为 TNotifyDownloading = procedure (FileName: PChar; ulProgress, ulProgressMax, ulStatusCode: ULONG; szStatusText: LPCWSTR) of object; 就可以实现进度回调( 下面就进入正式应用了 首先声明一个TBindStatusCallback类型的变量(这里设定为 BSC)然后创建它( function Download(Url: Pchar; FileName: Pchar; BSC: TBindStatusCallback): Boolean; begin result := (UrlDownloadToFile(nil, Url, FileName, 0, BSC) = S_OK); end; ...... var BSC: TBindStatusCallback; begin BSC:=TBindStatusCallback.Create; BSC.OnDownloading := Self.OnDownloading; if (Download('', 'c:\building.exe', BSC)) then ...下载成功 else ...下载失败 end; procedure OnDownloading(FileName: PChar; ulProgress, ulProgressMax, ulStatusCode: ULONG; szStatusText: LPCWSTR); begin 进度在此显示(((( end;