如何将线程函数的地址作为回调传递给winapi? [英] How to pass the address of a thread function as a callback to winapi?

问题描述

我有一个简单的线程，在执行过程中，我尝试使用该线程中定义的函数之一的地址调用EnumWindows(). 因此，我正在尝试执行以下操作:EnumWindows(@cbEnumWindowsClickOK，0);其中cbEnumWindowsClickOK是在线程类内部定义的EnumWindowProc，如下所示:

I have a simple thread and inside the execute I try to call EnumWindows() with the address of one of the functions defined in the thread. So I'm trying to do this: EnumWindows(@cbEnumWindowsClickOK, 0); where cbEnumWindowsClickOK is an EnumWindowProc defined inside the thread class, like so:

TAutoClickOKThread = class(TThread)
private
     fExitEvent : THandle;
     function cbEnumWindowsClickOK(Wnd: HWND; Info: Pointer): BOOL;
public
   constructor Create(ExitEvent : Thandle);
   procedure Execute(); override;
end;

尝试此操作时，我不断收到错误:需要变量"，暗示它没有将@cbEnumWindowsClickOK解释为地址.如果我将函数移到全局范围(从线程中移出)，它将起作用.

When I try this I keep getting "Error: Variable required", hinting that it doesn't interpret @cbEnumWindowsClickOK as an address. If I move the function to a global scope (removing it from the thread) it does work.

关于如何解决此问题的任何想法?

Any thoughts on how I can fix this?

推荐答案

您必须传递EnumWindows一个普通的旧函数，即未绑定到实例的函数.您必须单独传递实例.像这样:

You have to pass EnumWindows a plain old function, i.e. one that is not bound to an instance. You must pass the instance in separately. Like this:

function EnumFunc(hwnd: HWND; lParam: LPARAM): BOOL; stdcall;
begin
  Result := TAutoClickOKThread(lParam).cbEnumWindowsClickOK(hwnd);
  //note that there is now no need for the Info parameter
end;
...
procedure TAutoClickOKThread.Execute;
begin
  ...
  EnumWindows(EnumFunc, LPARAM(Self));
  ...
end;

必须这样做的原因是实例方法与EnumWindows所需的签名不匹配.实例方法有一个额外的隐式参数，其中包含实例引用，即Self.这样便可以引用实例成员.但是EnumFunc的签名不能满足此要求.

The reason it must be done this way is that an instance method does not match the required signature for EnumWindows. An instance method has an extra, implicit, parameter containing the instance reference, i.e. Self. This is how you are able to refer to instance members. But the signature for EnumFunc does not cater for this.

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