Question

我的应用程序可以从memo1中的每个网址下载一张图片。它使用idhttp.get并有一个跳过按钮。跳过后，它会下载下一张图片。

Q1：你是否有代码放入析构函数中，＆＃34;是什么代码？终止＆＃34;和＆＃34;等待＆＃34;？ 我在另一个网站上发现了这个：

destructor thread.destroy;
begin
try
Terminate;
If HTTP.Connected then HTTP.Disconnect;
finally
WaitFor;
FreeAndNil(HTTP);
end;
inherited;
end;

Q2：如何调用析构函数并使其正常工作？

问题3：您是否有提示（特别是安全问题）和其他代码？

我的申请代码：

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, IdBaseComponent, IdComponent, IdTCPConnection,
  IdTCPClient, IdHTTP;

type
       thread = class
  public
      Constructor Create; overload;
      Destructor  Destroy; override;
  end;

  TForm1 = class(TForm)
    IdHTTP1: TIdHTTP;
    Memo1: TMemo;
    Memo2: TMemo;
    Memo3: TMemo;
    startbutton: TButton;
    skipbutton: TButton;

    procedure startbuttonClick(Sender: TObject);
    procedure skipbuttonClick(Sender: TObject);
    procedure IdHTTP1Work(Sender: TObject; AWorkMode: TWorkMode;
      const AWorkCount: Integer);

         end;
var
  Form1: TForm1;
     http: tidhttp;
     s: boolean;
implementation

{$R *.dfm}

            constructor thread.Create;
begin
      HTTP := TIdHTTP.Create(nil);
      inherited ;
end;

           destructor thread.destroy;
begin
try

If HTTP.Connected then HTTP.Disconnect;
finally
FreeAndNil(HTTP);
end;
inherited;
end;


procedure TForm1.startbuttonClick(Sender: TObject);
var
i: integer;
  fs : TFileStream ;
begin
for i:= 0 to memo1.lines.count-1 do begin
s:= false;
   fs := TFileStream.Create(inttostr(i)+'abc.jpg', fmCreate);
   http:= idhttp1;
   try
   try
HTTP.Get(memo1.lines[i],fs);
memo2.Lines.add(memo1.Lines[i]);
except
on E: Exception do
begin
memo3.lines.add(' ha ha ha not working   '+syserrormessage(getlasterror));
end;
end;
finally
fs.free;
end;
end;

  end;

procedure TForm1.skipbuttonClick(Sender: TObject);
    begin
s:=true;
end;

procedure TForm1.IdHTTP1Work(Sender: TObject; AWorkMode: TWorkMode;
  const AWorkCount: Integer);
begin
application.ProcessMessages;

     if s = true then
http.Disconnect;

end;

end.

Answer 1

由于你在GUI（=主线程）中使用IdHttp并且Indy被阻止，你有两个选择：a）将IdAntifreeze与消息结合使用（只需删除表格上的组件），b）使用线程。

不要使用Application.Processmessages因为它会导致奇怪的副作用。

现在回答你的问题：

Q1 ：您在互联网上找到的代码实施的解决方案b）所以这不适用于您当前的代码

Q2 ：与Q1相同

Q3 ：这是一个正确实现解决方案的版本a）

这段代码仍然不是100％完美，因为它没有实现禁用/启用starttransfer和skiptransfer按钮的逻辑（我把它留作练习:)）。

unit Unit16;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, IdAntiFreezeBase, IdAntiFreeze, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient, IdHTTP;

const
  WM_TRANSFER = WM_USER + 1;

type
  TForm1 = class(TForm)
    IdHTTP1: TIdHTTP;
    IdAntiFreeze1: TIdAntiFreeze;
    Memo1: TMemo;
    Btn_start: TButton;
    Btn_skip: TButton;
    Memo2: TMemo;
    procedure IdHTTP1Work(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
    procedure Btn_startClick(Sender: TObject);
    procedure Btn_skipClick(Sender: TObject);
  private
    { Private declarations }
    Transferring : Boolean;
    UrlIndex : Integer;
    procedure NextTransfer(var msg : TMessage); message WM_TRANSFER;
    procedure StartTransfer;
    procedure DoTransfer;
    procedure SkipTransfer;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
procedure TForm1.NextTransfer(var msg: TMessage);
begin
 DoTransfer;
end;

procedure TForm1.SkipTransfer;
begin
 Transferring := false;
end;

procedure TForm1.StartTransfer;
begin
 UrlIndex := 0;
 DoTransfer;
end;

procedure TForm1.DoTransfer;

var
  Url : String;
  Stream : TStringStream;

begin
 if UrlIndex < Memo1.Lines.Count then
  begin
   Url := Memo1.Lines[UrlIndex];
   Memo2.Lines.Add(Format('getting data from URL: %s', [Url]));
   Inc(UrlIndex);
   Transferring := True;
   try
    Stream := TStringStream.Create;
    try
     IdHttp1.Get(Url, Stream);
     Memo2.Lines.Add(Format('Data: "%s"',[Stream.DataString]));
    finally
     Stream.Free;
    end;
   except
    on E: Exception do
     begin
      Memo2.Lines.Add(Format('error during transfer: %s', [E.Message]));
     end;
   end;
   Transferring := False;
   PostMessage(Handle, WM_TRANSFER, 0, 0);
  end;
end;

procedure TForm1.Btn_startClick(Sender: TObject);
begin
 Memo2.Lines.Add('starting transfer');
 StartTransfer;
end;

procedure TForm1.Btn_skipClick(Sender: TObject);
begin
 Memo2.Lines.Add('skipping current transfer');
 SkipTransfer;
end;

procedure TForm1.IdHTTP1Work(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
begin
  Memo2.Lines.Add('work event');
 if not Transferring and (AWorkMode = wmRead) then
 try
  Memo2.Lines.Add('disconnecting peer');
  IdHttp1.Disconnect;
 except
 end;
end;

end.

DFM档案：

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 290
  ClientWidth = 707
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Memo1: TMemo
    Left = 92
    Top = 12
    Width = 213
    Height = 257
    Lines.Strings = (
      'http://stackoverflow.com'
      'http://www.google.com'
      'http://www.hardocp.com'
      '')
    TabOrder = 0
    WordWrap = False
  end
  object Btn_start: TButton
    Left = 8
    Top = 128
    Width = 75
    Height = 25
    Caption = 'Btn_start'
    TabOrder = 1
    OnClick = Btn_startClick
  end
  object Btn_skip: TButton
    Left = 8
    Top = 159
    Width = 75
    Height = 25
    Caption = 'Btn_skip'
    TabOrder = 2
    OnClick = Btn_skipClick
  end
  object Memo2: TMemo
    Left = 320
    Top = 12
    Width = 373
    Height = 257
    TabOrder = 3
    WordWrap = False
  end
  object IdHTTP1: TIdHTTP
    OnWork = IdHTTP1Work
    AllowCookies = True
    ProxyParams.BasicAuthentication = False
    ProxyParams.ProxyPort = 0
    Request.ContentLength = -1
    Request.ContentRangeEnd = -1
    Request.ContentRangeStart = -1
    Request.ContentRangeInstanceLength = -1
    Request.Accept = 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
    Request.BasicAuthentication = False
    Request.UserAgent = 'Mozilla/3.0 (compatible; Indy Library)'
    Request.Ranges.Units = 'bytes'
    Request.Ranges = <>
    HTTPOptions = [hoForceEncodeParams]
    Left = 24
    Top = 16
  end
  object IdAntiFreeze1: TIdAntiFreeze
    Left = 16
    Top = 72
  end
end

停止idhttp.get时的析构函数（indy，delphi）

1 个答案: