多線程編程(9) - 認(rèn)識(shí)等待函數(shù) WaitForSingleObject
一下子跳到等待函數(shù) WaitForSingleObject, 是因?yàn)橄旅娴腗utex、Semaphore、Event、WaitableTimer 等同步手段都要使用這個(gè)函數(shù); 不過(guò)等待函數(shù)可不止WaitForSingleObject 它一個(gè), 但它最簡(jiǎn)單. function WaitForSingleObject( hHandle: THandle; {要等待的對(duì)象句柄} dwMilliseconds: DWORD {等待的時(shí)間, 單位是毫秒} ): DWORD; stdcall; {返回值如下:} WAIT_OBJECT_0 {等著了, 本例中是: 等的那個(gè)進(jìn)程終于結(jié)束了} WAIT_TIMEOUT {等過(guò)了點(diǎn)(你指定的時(shí)間), 也沒(méi)等著} WAIT_ABANDONED {好不容易等著了, 但人家還是不讓咱執(zhí)行; 這一般是互斥對(duì)象} //WaitForSingleObject 的第二個(gè)參數(shù)一般給常數(shù)值 INFINITE, 表示一直等下去, 死等. WaitForSingleObject 等待什么? 在多線程里就是等待另一個(gè)線程的結(jié)束, 快來(lái)執(zhí)行自己的代碼; 不過(guò)它可以等待的對(duì)象可不止線程; 這里先來(lái)一個(gè)等待另一個(gè)進(jìn)程結(jié)束的例子, 運(yùn)行效果圖:
代碼文件:unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type TForm1 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); end; var Form1: TForm1; implementation {$R *.dfm} var hProcess: THandle; {進(jìn)程句柄} {等待一個(gè)指定句柄的進(jìn)程什么時(shí)候結(jié)束} function MyThreadFun(p: Pointer): DWORD; stdcall; begin if WaitForSingleObject(hProcess, INFINITE) = WAIT_OBJECT_0 then Form1.Text := Format('進(jìn)程 %d 已關(guān)閉', [hProcess]); Result := 0; end; {啟動(dòng)一個(gè)進(jìn)程, 并建立新線程等待它的結(jié)束} procedure TForm1.Button1Click(Sender: TObject); var pInfo: TProcessInformation; sInfo: TStartupInfo; Path: array[0..MAX_PATH-1] of Char; ThreadID: DWORD; begin {先獲取記事本的路徑} GetSystemDirectory(Path, MAX_PATH); StrCat(Path, 'notepad.exe'); {用 CreateProcess 打開(kāi)記事本并獲取其進(jìn)程句柄, 然后建立線程監(jiān)視} FillChar(sInfo, SizeOf(sInfo), 0); if CreateProcess(Path, nil, nil, nil, False, 0, nil, nil, sInfo, pInfo) then begin hProcess := pInfo.hProcess; {獲取進(jìn)程句柄} Text := Format('進(jìn)程 %d 已啟動(dòng)', [hProcess]); CreateThread(nil, 0, @MyThreadFun, nil, 0, ThreadID); {建立線程監(jiān)視} end; end; end.
窗體文件:object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeight = 124 ClientWidth = 241 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False PixelsPerInch = 96 TextHeight = 13 object Button1: TButton Left = 88 Top = 56 Width = 75 Height = 25 Caption = 'Button1' TabOrder = 0 OnClick = Button1Click end end
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