線程中的句柄錯誤無效

Question

當我嘗試使用此線程但我看不到問題時，我總是收到「線程錯誤：句柄無效（6）」。如果可以，請幫助，謝謝！

stackoverlow抱怨說我沒有足夠的解釋。所以，我創建了一個沒有任何錯誤編譯的線程類，但是當我用execute調用它時似乎運行正常，但是在析構函數中拋出了這個錯誤。

tdownloadthread = class(tthread) 
    private 
     furl, 
     ffilename, 
     fmsg: string; 
     fdl: tidhttp; 
     readings,bpstotal,avgbps: int64; 
     fpercent: word; 
     fsuccess,fcanceled: boolean; 
     start: tdatetime; 
     fspeed,fremaining: string; 
    public 
     constructor create(url,filename: string); 
     destructor destroy; override; 
     procedure execute; override; 
     procedure DlWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64); 
     procedure cancel; 

     property success: boolean read fsuccess; 
     property canceled: boolean read fcanceled; 
     property speed: string read fspeed; 
     property percent: word read fpercent; 
     property remaining: string read fremaining; 
     property msg: string read fmsg; 
    end; 


constructor tdownloadthread.create(url,filename: string); 
begin 
    fsuccess:=false; 
    fcanceled:=false; 

    fdl:=tidhttp.Create(nil); 
    fdl.OnWork:=dlwork; 
    fdl.HandleRedirects:=true; 

    furl:=url; 
    ffilename:=filename; 

    freeonterminate:=false; 
end; 

destructor tdownloadthread.Destroy; 
begin 
    fdl.Free; 
end; 

procedure tdownloadthread.cancel; 
begin 
    fdl.Disconnect; 
    fcanceled:=true; 
end; 

procedure tdownloadthread.DlWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64); 
var 
    Http: TIdHTTP; 
    ContentLength: Int64; 
    i,h,m,esec,sec,rsec,bps: Integer; 
    f: tdatetime; 
begin 
    Http := TIdHTTP(ASender); 
    ContentLength := Http.Response.ContentLength; 

    if (Pos('chunked', LowerCase(Http.Response.ResponseText)) = 0) and 
    (ContentLength > 0) then 
    begin 
    fpercent := trunc(100*(AWorkCount/ContentLength)); 

    esec := secondsbetween(now, start); 

    if (avgbps > 0) then 
    begin 
     i:=contentlength div avgbps; 
     f:=incsecond(now, i); 
     rsec:=secondsbetween(now, f); 

     sec:=rsec - esec; 

     h:=sec div 3600; 
     m:=sec div 60 - H * 60; 
     sec:=sec - (H * 3600 + M * 60) ; 
    end; 

    if (esec > 0) then 
     bps:=(aworkcount div esec) 
     else 
     bps:=0; 

    inc(readings); 
    inc(bpstotal, bps); 
    avgbps:=bpstotal div readings; 

    if (avgbps/1024 < 1024) then 
     fspeed:=format('%2f KB/s', [avgbps/1024]) 
     else 
     fspeed:=format('%2f MB/s', [(avgbps div 1024)/1024]); 

    fremaining:=format('%s m %s s', [zero(m), zero(secno)]); 
    end; 
end; 

procedure tdownloadthread.Execute; 
var fn,cd: string; 
    data: tmemorystream; 
begin 
    try 
    start:=now; 

    data:=tmemorystream.Create; 

    fdl.Get(furl, data); 
    cd:=fdl.Response.ContentDisposition; 
    if (pos('filename=', cd) > 0) then 
     fn:=extractfilepath(paramstr(0))+copy(cd, pos('=', cd)+1, length(cd)) 
     else 
     fn:=ffilename; 
    data.SaveToFile(fn); 
    ffilename:=fn; 
    fsuccess:=true; 

    data.Free; 
    except 
    on e: exception do 
     begin 
     fsuccess:=false; 
     fmsg:=e.Message; 
     end; 
    end; 
end; 

procedure testdownload; 
var downloadthread: tdownloadthread; 
begin 
    downloadthread:=tdownloadthread.create('http://www.someurl.com/filename.old',extractfilepath(paramstr(0))+'filename.new'); 
    downloadthread.Execute; 
    if downloadthread.canceled then showmessage('canceled'); 
    if downloadthread.success then showmessage('success'); 
    if not downloadthread.success then showmessage('error: '+downloadthread.msg); 
    downloadthread.Free; 
end; 

Answer 1

你忘了呼籲的TThread繼承的構造函數：

constructor tdownloadthread.create(url,filename: string); 
begin 
    inherited create(true); // construct TThread 
    fsuccess:=false; 
    fcanceled:=false; 

    fdl:=tidhttp.Create(nil); 
    fdl.OnWork:=dlwork; 
    fdl.HandleRedirects:=true; 

    furl:=url; 
    ffilename:=filename; 

    freeonterminate:=false; 
    resume; // actually run thread 
end; 

此外，由@LU RD poinnted出來，沒有必要直接調用的TThread實例的execute（）方法 - 線程直接由操作系統執行。

至於釋放它，有一些選擇。按照優先順序排列：

1）不要釋放它。如果您打算在您的應用程序運行期間進行多次下載，請將線程循環到生產者 - 使用者隊列彈出窗口中，以便線程可以重新用於下載更多文件，而不必嘗試釋放它。

2）在try/finally中釋放其內部資源（例如TidHTTP實例）後讓線程實例釋放自身（freeOnTerminate = true）。

-999999）使用OnTerminate處理程序或任何其他可怕的Delphi TThread的東西，如TThread.WaitFor。