Question

vc++的MessageBox的问题

输出1元2次方程的根··本来是TextOut(hdc,10,90,str,strlen(str));可以，现在想改成弹出对话框输出，，怎么运行不对··
怎么改···
#include<windows.h>
#include<math.h>
#include<stdio.h>
int GetRoot(float a,float b,float c,double *root)
{double delta,deltasqrt;
delta=b*b-4.0*a*c;
if(delta<0.0)return 0;
deltasqrt=sqrt(delta);
if(a!=0){
root[0]=(-b+deltasqrt)/(2.0*a);
root[1]=(-b-deltasqrt)/(2.0*a);
}
else
if(b!=0)root[0]=root[1]=-c/b;
else return 0;
if(root[0]==root[1])return 1;
else return 2;
}
char str[80];
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style =CS_HREDRAW|CS_VREDRAW;
wndclass.lpfnWndProc =WndProc;
wndclass.cbClsExtra =0;
wndclass.cbWndExtra =0;
wndclass.hInstance =hInstance;
wndclass.hIcon =LoadIcon(NULL,IDI_APPLICATION);
wndclass.hCursor =LoadCursor(NULL,IDC_ARROW);
wndclass.hbrBackground =(HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName =NULL;
wndclass.lpszClassName ="HelloWin";
if(!RegisterClass(&wndclass))
{
MessageBox(NULL,"窗口注册失败!","HelloWin",0);
return 0;
}
hwnd=CreateWindow("HelloWin",
"我的窗口",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
hInstance,
NULL);
ShowWindow(hwnd,nCmdShow);
UpdateWindow(hwnd);
while(GetMessage(&msg,NULL,0,0))
{TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{ HDC hdc;
PAINTSTRUCT ps;
static HWND hwndButton,hwndEdit[3];
char strEdit[80];
float a[3];
double root[2];
int i;

switch(message){
case WM_CREATE:
hwndEdit[0]=CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,10,60,100,25,hwnd,NULL,NULL,NULL);
hwndEdit[1]=CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,120,60,100,25,hwnd,NULL,NULL,NULL);
hwndEdit[2]=CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,230,60,100,25,hwnd,NULL,NULL,NULL);
hwndButton=CreateWindow("button","Show",WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON,340,60,80,25,hwnd,NULL,NULL,NULL);

return 0;
case WM_COMMAND:
if(((HWND)lParam==hwndButton)&&(HIWORD(wParam)==BN_CLICKED))
{for(i=0;i<3;i++){
GetWindowText(hwndEdit[i],strEdit,80);
a[i]=(float)atof(strEdit);
}
int n=GetRoot(a[0],a[1],a[2],root);
if(n<1) strcpy(str,"NO");
else sprintf(str,"fsaf:%f,%f",root[0],root[1]);
InvalidateRect(hwnd,NULL,TRUE);
}
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
MessageBox(NULL,str,"show",0);
EndPaint(hwnd,&ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd,message,wParam,lParam);
}

Answer 1

是可以显示的。不过窗口形成时出现了重绘，把空的字符给重绘出来了。。
所以加个判断就行了
if (strlen(str) != 0)
{
MessageBox(NULL,str,"show", MB_OK);
}
改后完整程序如下。
#include<windows.h>
#include<math.h>
#include<stdio.h>
int GetRoot(float a,float b,float c,double *root)
{
double delta,deltasqrt;
delta=b*b-4.0*a*c;
if(delta<0.0)return 0;
deltasqrt=sqrt(delta);
if(a!=0){
root[0]=(-b+deltasqrt)/(2.0*a);
root[1]=(-b-deltasqrt)/(2.0*a);
}
else
if(b!=0)root[0]=root[1]=-c/b;
else return 0;
if(root[0]==root[1])return 1;
else return 2;
}
char str[80];
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style =CS_HREDRAW|CS_VREDRAW;
wndclass.lpfnWndProc =WndProc;
wndclass.cbClsExtra =0;
wndclass.cbWndExtra =0;
wndclass.hInstance =hInstance;
wndclass.hIcon =LoadIcon(NULL,IDI_APPLICATION);
wndclass.hCursor =LoadCursor(NULL,IDC_ARROW);
wndclass.hbrBackground =(HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName =NULL;
wndclass.lpszClassName ="HelloWin";
if(!RegisterClass(&wndclass))
{
MessageBox(NULL,"窗口注册失败!","HelloWin",0);
return 0;
}
hwnd=CreateWindow("HelloWin",
"我的窗口",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
hInstance,
NULL);
ShowWindow(hwnd,nCmdShow);
UpdateWindow(hwnd);
while(GetMessage(&msg,NULL,0,0))
{TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{ HDC hdc;
PAINTSTRUCT ps;
static HWND hwndButton,hwndEdit[3];
char strEdit[80];
float a[3];
double root[2];
int i;

switch(message){
case WM_CREATE:
hwndEdit[0]=CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,10,60,100,25,hwnd,NULL,NULL,NULL);
hwndEdit[1]=CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,120,60,100,25,hwnd,NULL,NULL,NULL);
hwndEdit[2]=CreateWindow("edit",NULL,WS_CHILD|WS_VISIBLE|WS_BORDER,230,60,100,25,hwnd,NULL,NULL,NULL);
hwndButton=CreateWindow("button","Show",WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON,340,60,80,25,hwnd,NULL,NULL,NULL);

return 0;
case WM_COMMAND:
if(((HWND)lParam==hwndButton)&&(HIWORD(wParam)==BN_CLICKED))
{for(i=0;i<3;i++){
GetWindowText(hwndEdit[i],strEdit,80);
a[i]=(float)atof(strEdit);
}
int n=GetRoot(a[0],a[1],a[2],root);
if(n<1) strcpy(str,"NO");
else sprintf(str,"fsaf:%f,%f",root[0],root[1]);

InvalidateRect(hwnd,NULL,TRUE);
}
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
if (strlen(str) != 0)
{
MessageBox(NULL,str,"show", MB_OK);
}
EndPaint(hwnd,&ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd,message,wParam,lParam);
}

Answer 2

if(messagebox("选择是否执行",null,mb_yesno)==idyes)
{
afxmessagebox("ss");
//这里写你要执行的代码
}
----------------------------------------------
例子：要引入头文件windows.h
#include<iostream.h>
#include<windows.h>
void
main(){
if(messagebox(null,"是否打印?","choose",mb_yesno)==idyes)
{
cout<<"sss";
}
}
--------------------------------
当然也可以用mfc做。。由于生成的文件较多，就不贴了

Answer 3

从VC2005开始，默认是Unicode，
你要改成MessageBox(_T("Message"),_T("Title"),MB_ICONINFORMATION|MB_OK);
或者MessageBox(L("Message"),L("Title"),MB_ICONINFORMATION|MB_OK);