钩子报内存错误。。急。。。

Question

我在DLL里定义一个鼠标钩子，可是在鼠标点击某些窗口后，会报内存异常，通常是点了某个窗口之后的时候，就报错误，显示“指定内存引用0xxxxxx ，该内存不能written”我的系统是xp，用的是delphi2006。大家指点一下，到底是什么原因，急死我了。 
先谢谢大家了。

Answer 1

我的代码是这样的：
unit unithook;interface
uses windows,Messages,Udllconst,SysUtils,Graphics,Classes,Dialogs;var
h: HHook;
hMappingFile: THandle;
PShMem: PShareMem;function StartHook(sender: HWND;messageID: LongInt):boolean;stdcall;
function StopHook:boolean;stdcall;implementationfunction hookproc(nCode: Integer;wParam: WPARAM;lParam: LPARAM):LRESULT;stdcall;
var
  aRect,R :TRect;//reRect: TRect;
  dc: hdc;
  Mycan: TCanvas;
  Mybmp: TBitmap;
begin
  Result := 0;
  if nCode < 0 then
    Result := CallNextHookEx(h,nCode,wparam,lparam);
  case wparam of
    WM_LBUTTONDOWN,WM_NCLBUTTONDOWN :
      begin
        if pShMem^.data1[1] = pMOUSEHOOKSTRUCT(lparam)^.hwnd then
              exit;
        if not pShMem^.SeCapBMP then
          begin
            
            if (pMOUSEHOOKSTRUCT(lparam)^.pt.X > pShMem^.SeRect.Left)  and
               (pMOUSEHOOKSTRUCT(lparam)^.pt.X < pShMem^.SeRect.Right) and
               (pMOUSEHOOKSTRUCT(lparam)^.pt.Y > pShMem^.SeRect.Top)   and
               (pMOUSEHOOKSTRUCT(lparam)^.pt.Y < pShMem^.SeRect.Bottom) then
              begin
                //Showmessage('222');
                pShMem^.data2:=pMOUSEHOOKSTRUCT(lparam)^;
                aRect := Rect(pShMem^.SeRect.Left+3,pShMem^.SeRect.Top+3,pShMem^.SeRect.Right-2,pShMem^.SeRect.Bottom-2);
                Mybmp := Tbitmap.Create;
                if (pShMem^.MyHandle =0)or(pShMem^.MyHandle <> pShMem^.data2.hwnd) then
                  begin
                    //reRect := Rect(aRect.Left-3,aRect.Top-3,aRect.Right+3,arect.Bottom+3);
                    //ShowMessage('111');
                    Mycan := TCanvas.Create;
                    dc := GetWindowDC(0);
                    try
                      Mycan.Handle := dc;
                      Mybmp.Width := aRect.Right - aRect.Left;
                      Mybmp.Height := aRect.Bottom - aRect.Top;
                      R := Rect(0,0,Mybmp.width,Mybmp.Height);
                      Mybmp.Canvas.CopyRect(R, Mycan,aRect);
                    finally
                      releaseDC(0, DC);
                    end;
                    Mycan.Handle := 0;
                    Mycan.Free;
                    Inc(pShMem^.BMPIndex);
                    pShMem^.MyHandle := pShMem^.data2.hwnd;
                  end
                else
                  Mybmp.LoadFromFile('D:\program\DemoCreator截屏预研\output\copy'+IntToStr(pShMem^.BMPIndex)+'.BMP');
                Mybmp.Canvas.Pen.Color := clBlue;
                Mybmp.Canvas.Brush.Style := BsClear;
                Mybmp.Canvas.Rectangle(Rect(pShMem^.data2.pt.X-aRect.Left-3,pShMem^.data2.pt.Y-aRect.Top-3,pShMem^.data2.pt.X-aRect.Left+28,pShMem^.data2.pt.Y-aRect.Top+15));
                Mybmp.Canvas.TextOut(pShMem^.data2.pt.X-aRect.Left,pShMem^.data2.pt.Y-aRect.Top,'Click');
                Mybmp.SaveToFile('D:\program\DemoCreator截屏预研\output\copy'+IntToStr(pShMem^.BMPIndex)+'.BMP');
                Mybmp.Free;
              end;
          end；
  end;
end;function StartHook(sender: HWND;messageID: LongInt):boolean;stdcall;
begin
Result := false;
if h = 0 then
  begin
    pShMem^.data1[1]:=sender;
    pShMem^.data1[2]:=messageid;
    h := SetWindowsHookEx(WH_MOUSE,@hookProc,Hinstance,0);
    Result := true;
  end;
end;function StopHook:boolean;stdcall;
begin
Result := false;
if h <> 0 then
  begin
    UnHookWindowsHookEx(h);
    h := 0;
    Result := true;
  end;
end;Initialization
  hMappingFile := OpenFileMapping(FILE_MAP_WRITE,False,MappingFileName);
  if hMappingFile=0 then
    hMappingFile := CreateFileMapping($FFFFFFFF,nil,PAGE_READWRITE,0,SizeOf(TShareMem),MappingFileName);
  if hMappingFile=0 then Exception.Create('不能建立共享内存!');
    pShMem :=  MapViewOfFile(hMappingFile,FILE_MAP_WRITE or FILE_MAP_READ,0,0,0);
  if pShMem = nil then
    begin
      CloseHandle(hMappingFile);
      Exception.Create('不能映射共享内存!');
    end;
  h := 0;
  pShMem^.MyHandle := 0;
  pShMem^.BMPIndex := 0;finalization
  try
    UnMapViewOfFile(pShMem);
    //pShMem := nil;
    CloseHandle(hMappingFile);
    //hMappingFile := 0;
  except
    ShowMessage('problem!');
  end;
end.