ShowWindow错误,GetLastError返回400，怎么回事?

Question

ERROR_THREAD_MODE_ALREADY_BACKGROUND
400 (0x190) The thread is already in background processing mode.怎么回有这样的错误? 我写了一个很简单的Win32程序，只是想显示一个最简单的窗口，如下代码:
#include<Windows.h>
#include<stdio.h>
const char className[]="mywndclass";
LRESULT __stdcall myproc(HWND hWnd,UINT uMsg,WPARAM wp,LPARAM lp){
return 0L;
}
int __stdcall WinMain(
HINSTANCE hInst,
HINSTANCE hPrev,
LPSTR lpCmdLine,
int nCmdShow
){
WNDCLASSEX wnd;
ZeroMemory(&wnd,sizeof(wnd));
wnd.cbSize=sizeof(wnd);
wnd.lpszClassName=className;
wnd.lpszMenuName=NULL;
wnd.hInstance=hInst;
wnd.lpfnWndProc=myproc;
wnd.hbrBackground=(HBRUSH)MAKEINTRESOURCE(GRAY_BRUSH);
HWND hWnd=CreateWindowEx(0,className,"窗口名称",0,0,0,300,200,NULL,NULL,hInst,0);
if(INVALID_HANDLE_VALUE==hWnd){
MessageBox(NULL,"Error!","CreateWindowEx失败\n",MB_OK);
return 1;
}
if(!ShowWindow(hWnd,SW_SHOW)){
char dip[200];
sprintf(dip,"ShowWindow失败:%d\n",GetLastError());
MessageBox(NULL,"Error!",dip,MB_OK);
return 1;
}
return 0;
}

Answer 1

就一个最简单的exe啊，别的什么也没有。
winproc是空的，这个没有什么问题吧

Answer 2

RegisterClassEx(&wnd);     HWND hWnd=CreateWindowEx(0,className,"窗口名称", WS_OVERLAPPEDWINDOW |  WS_HSCROLL |   WS_VSCROLL
,0,0,300,200,NULL,NULL,hInst,0);
    if(!hWnd){
        MessageBox(NULL,"Error!","CreateWindowEx失败\n",MB_OK);
        return 1;
    }

Answer 3

1）加入RegisterClassEx
2）判断hwnd，应该是非0，而不是-1。

Answer 4

++也需看看ShowWindow返回码的描述：
Nonzero indicates that the window was previously visible. Zero indicates that the window was previously hidden. 

Answer 5

我按照你说的两条改了一下。但是问题是现在CreateWindowEx虽然成功了(GetLastError=0)，但是返回hWnd=0!
这是为什么呢? 
现在的代码是:#include<Windows.h>
#include<stdio.h>
const char className[]="mywndclass";
LRESULT __stdcall myproc(HWND hWnd,UINT uMsg,WPARAM wp,LPARAM lp){
return 0L;
}
int __stdcall WinMain(
HINSTANCE hInst,
HINSTANCE hPrev,
LPSTR lpCmdLine,
int nCmdShow
){
WNDCLASSEX wnd;
ZeroMemory(&wnd,sizeof(wnd));
wnd.cbSize=sizeof(wnd);
wnd.lpszClassName=className;
wnd.lpszMenuName=NULL;
wnd.hInstance=hInst;
wnd.lpfnWndProc=myproc;
wnd.hbrBackground=(HBRUSH)MAKEINTRESOURCE(GRAY_BRUSH);
ATOM reg;
if((reg=RegisterClassEx(&wnd))==0){
MessageBox(NULL,"RegisterClassEx失败\n","有错!",MB_OK);
return 1;
}
char dip[200];
HWND hWnd=CreateWindowEx(0,className,"窗口名称",
WS_OVERLAPPEDWINDOW |  WS_HSCROLL |   WS_VSCROLL,0,0,300,200,NULL,NULL,hInst,0);
if(0==hWnd){
sprintf(dip,"CreateWindowEx失败:%d\n",GetLastError());
MessageBox(NULL,dip,"有错r!",MB_OK);
return 1;
}
if(!ShowWindow(hWnd,SW_SHOW)){
sprintf(dip,"ShowWindow失败:%d\n",GetLastError());
MessageBox(NULL,dip,"有错!",MB_OK);
return 1;
}
return 0;
}

Answer 6

你并没有注册窗口类
RegisterClassEx并且尚需判断窗口是否创建成功
IsWindow

Answer 7

照msdn的demo写就行了，俺就是比较着改的。我那窗口也没出来，懒得调了。// test.cpp : Defines the entry point for the application.
//#include "stdafx.h"
#include<Windows.h>
#include<stdio.h>
char className[]="mywndclass";
LRESULT __stdcall myproc(HWND hWnd,UINT uMsg,WPARAM wp,LPARAM lp){
MSG msg;
    while (GetMessage(&msg, (HWND) NULL, 0, 0) != 0 && GetMessage(&msg, (HWND) NULL, 0, 0) != -1) 
    { 
        TranslateMessage(&msg); 
        DispatchMessage(&msg); 
    } return 0;
}
int __stdcall WinMain(
    HINSTANCE hInst,
    HINSTANCE hPrev,
    LPSTR lpCmdLine,
    int nCmdShow
){
    WNDCLASSEX wnd;
    ZeroMemory(&wnd,sizeof(wnd));
    wnd.cbSize=sizeof(wnd);
    wnd.lpszClassName=className;
    wnd.lpszMenuName=NULL;
    wnd.hInstance=hInst;
    wnd.lpfnWndProc=myproc;
    wnd.hbrBackground=(HBRUSH)MAKEINTRESOURCE(GRAY_BRUSH);
RegisterClassEx(&wnd);     HWND hWnd=CreateWindowEx(0,className,"窗口名称", WS_OVERLAPPEDWINDOW |  WS_HSCROLL |   WS_VSCROLL
,0,0,300,200,NULL,NULL,hInst,0);
    if(!hWnd){
        MessageBox(NULL,"Error!","CreateWindowEx失败\n",MB_OK);
        return 1;
    }
    if(!ShowWindow(hWnd,SW_SHOW)){
        char dip[200];
        sprintf(dip,"ShowWindow失败:%d\n",GetLastError());
        MessageBox(NULL,"Error!",dip,MB_OK);
        return 1;
    }
    return 0;
}