基于Win32的应用程序,尝试更新标签的文本

Question

此代码显示一个带有文本标签的窗口,上面写着:"请输入一个数字"和一个按钮.

单击按钮时,应将文本替换为"TEXT".它可以工作,但它会在第一个文本的顶部写入/打印新文本.所以它的重叠.

我想要更改文本字符串而不是写第一个,但我不知道我是如何对Windows应用程序开发的新手.

请帮帮我们.

整个来源是:

#include <windows.h>
#include <iostream>


using namespace std;


enum { ID_LABEL = 1,ID_BUTTON0};

static  HWND static_label, button0;

HDC          hdc;
HBRUSH  NewBrush;
HINSTANCE g_hInst;


LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);


int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
    LPCTSTR className = TEXT("myClass");
    WNDCLASSEX wc;

    wc.cbSize        = sizeof(wc);
    wc.style         = CS_HREDRAW | CS_VREDRAW;
    wc.cbWndExtra    = 0;
    wc.cbClsExtra    = 0;
    wc.lpfnWndProc   = WndProc;
    wc.hInstance     = hInstance;
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = TEXT("myClass");


    wc.hbrBackground  = (HBRUSH)(CreateSolidBrush(RGB(48, 38, 88)));

    wc.hIcon             = LoadIcon(NULL, IDI_APPLICATION);
    wc.hIconSm           = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor           = LoadCursor(NULL, IDC_ARROW);

    if(!RegisterClassEx(&wc))
    {
        MessageBox(NULL, TEXT("ERROR! FAILED TO REGISTER CLASS!"), TEXT("FATAL ERROR!"), MB_IConerror | MB_OK);
        return 1;
    }

    HWND hwnd = CreateWindowEx(0, TEXT("myClass"), TEXT("WINDOW TITLE"), WS_OVERLAPPEDWINDOW, 450, 100, 500 + 7, 500 + 33 , NULL, NULL, hInstance, NULL);

    if(!hwnd)
    {
        MessageBox(NULL, TEXT("ERROR! FAILED TO CREATE WINDOW!"), TEXT("FATAL ERROR!"), MB_IConerror | MB_OK);

        return true;
    }  

    ShowWindow(hwnd, nShowCmd);                
    UpdateWindow(hwnd); 

    MSG msg;

    while(GetMessage(&msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return (int)msg.wParam;
}



LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
        case WM_PAINT:
        {

        }

        case WM_CTLCOLORSTATIC:
        {
           SetBkMode((HDC) wParam, TRANSPARENT);        

           return (LONG) GetStockObject(NULL_BRUSH);
    }

    break;

    case WM_CREATE:
    {
        static_label = CreateWindow(L"Static",L"Please Enter A Number",WS_CHILD | WS_VISIBLE,35,15,175,25,hwnd,0, g_hInst,0);

        button0 = CreateWindow(L"Button",L"OK",BS_PUSHBUTTON | WS_CHILD | WS_VISIBLE ,80,220,35,35,hwnd,(HMENU)ID_BUTTON0,g_hInst,0);   
      }

      break;

      case WM_COMMAND: //Command from Child windows and menus are under this message

      switch(wParam) //the ID is wParam
      {
         case ID_BUTTON0: //check for our button ID
         {
             SetWindowText(static_label,L"TEXT");

             break;
         }
      }//switch. 

  break;

  case WM_DESTROY: 
         PostQuitMessage(0);
         break; // pass to DefWindowProc(...) as well

      case WM_CLOSE:
         DestroyWindow(hwnd);
         break;
   } 

    return DefWindowProc(hwnd, msg, wParam, lParam);    
}

Answer 1

问题出在这里:

case WM_CTLCOLORSTATIC:
{
   SetBkMode((HDC) wParam, TRANSPARENT);        
   return (LONG) GetStockObject(NULL_BRUSH);
}

此代码告诉静态控件绘制没有背景颜色的文本,而不是重绘背景.因此,新文本将在旧文本之上而不是在新背景上绘制.

如果你需要一些自定义背景来显示,那么你将不得不使底层父窗口的那部分无效,并可能使用类似的东西WS_EX_TRANSPARENT来确保最后绘制子静态控件.这样,当它尝试绘制新文本时,应该绘制新的背景.

请注意,这意味着您无法WS_CLIPCHILDREN在底层父窗口上使用,这会在重绘事物时增加闪烁.