Win32 C++中的GetWindowText()不起作用

Question

下面的代码不起作用.我正在尝试从编辑控件获取文本,但它不起作用.厌倦了尝试所有可能的代码查看msdn等文档...

case WM_COMMAND:
    switch(LOWORD(wParam)){
    case 1:
        ::MessageBox(hwnd,"button clicked","message",MB_OK);
        break;
    case 2: 
        TCHAR t[20]; // 
            GetWindowText(text_box,t,19);// this is not working????????????????
        ::MessageBox(hwnd,t,t,MB_OK);
        cout<<t;



        break;

以下是完整的代码:

#include <windows.h>
#include<iostream>
using namespace std;

const char g_szClassName[] = "myWindowClass";

// Step 4: the Window Procedure
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    HWND text_field, button , text_box;
    char text_saved[20];

    switch(msg)

    {   case WM_CREATE:
         text_field = CreateWindow("STATIC",
            "Hello World",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,20, 90,25,
            hwnd,
            NULL,NULL,NULL);
        button = CreateWindow("BUTTON",
            "push button",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,50, 100,20,
            hwnd,
            (HMENU)1,NULL,NULL  
            )  ;
        text_box = CreateWindow("EDIT",
            " ",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,80, 200,25,
            hwnd,
            NULL,NULL,NULL
            );
        CreateWindow("BUTTON",
            "Save",
            WS_VISIBLE | WS_CHILD | WS_BORDER,
            20,120, 100,20,
            hwnd,
            (HMENU)2,NULL,NULL  
            );





    break;
    case WM_COMMAND:
        switch(LOWORD(wParam)){
        case 1:
            ::MessageBox(hwnd,"button clicked","message",MB_OK);
            break;
        case 2: 
            TCHAR t[20];
                GetWindowText(text_box,t,19);
            ::MessageBox(hwnd,t,t,MB_OK);
            cout<<t;



            break;



    }
    break;

        case WM_CLOSE:
            DestroyWindow(hwnd);
        break;
        case WM_DESTROY:
            PostQuitMessage(0);
        break;
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
    HWND hwnd;
    MSG Msg;

    //Step 1: Registering the Window Class
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = 0;
    wc.lpfnWndProc   = WndProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = g_szClassName;
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wc))
    {
        MessageBox(NULL, "Window Registration Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    // Step 2: Creating the Window
    hwnd = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        g_szClassName,
        "The title of my window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 500,500,
        NULL, NULL, hInstance, NULL);

    if(hwnd == NULL)
    {
        MessageBox(NULL, "Window Creation Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    // Step 3: The Message Loop
    while(GetMessage(&Msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;
 }  

Answer 1

您已将text_box(和其他变量)定义为WndProc函数的本地变量,这意味着每次调用该函数来处理消息时,它们的值都会丢失.static如果要将值从一个消息保留到下一个消息,则需要将它们移出函数作用域(或使它们).