用按键来控制页面的:
case WM_KEYDOWN:
注意，数字和字母的虚拟键码是ASCII码。Windows程序几乎从不使用这些虚拟键码
wParam消息参数含有上面所讨论的虚拟键码

WM_PAINT: 重绘消息 当窗口状态发生变化的时候都会被触发
1.获得HDC BeginPaint（窗口句柄，定义结构体）
2绘画
3.交还HDC endpaint（窗口句柄，结构体地址）

其他要重绘消息时
1.获得HDC GetDC（窗口句柄)
2.绘画
3.ReleaseDC（窗口句柄 ，hdc）
绘画时，可以购买画刷和使用画刷
购买画刷：CreateSolidBrush(RGB(0,255,0));
使用画刷： SelectObject(hdc,brush);

#include <Windows.h>
#include <stdio.h>

LRESULT CALLBACK My_WNDPROC(HWND hwnd, UINT message, WPARAM wPAREAM, LPARAM lPARAM);

int CALLBACK WinMain(
	HINSTANCE hInstance,
	HINSTANCE hPrevInstance,
	LPSTR lpCmdLine,
	int nCmdShow
	)
{
	WNDCLASSEX ex;
	HWND hwnd;
	MSG msg;

	ex.style = CS_HREDRAW | CS_VREDRAW;
	ex.cbSize = sizeof(ex);
	ex.cbClsExtra = 0;
	ex.cbWndExtra = 0;
	ex.hInstance = hInstance;
	ex.hIcon = NULL;
	ex.hCursor = NULL;
	ex.hbrBackground = CreateSolidBrush(RGB(0,128,128));
	ex.hIconSm = NULL;
	ex.lpfnWndProc = &My_WNDPROC;
	ex.lpszMenuName = NULL;
	ex.lpszClassName = "111";

	RegisterClassEx(&ex);

	hwnd = CreateWindow(ex.lpszClassName,"原谅他",WS_OVERLAPPEDWINDOW,50,50,500,500,NULL,NULL,hInstance,NULL);   

	ShowWindow(hwnd,SW_SHOW);

	/*SetTimer(hwnd,1,1000,NULL);*/
	while(GetMessage(&msg,NULL,0,0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return 0;
}

LRESULT CALLBACK My_WNDPROC(HWND hwnd, UINT message, WPARAM wPAREAM, LPARAM lPARAM)
{
	int x;
	int y;
	char str[10] = {0};
	HDC hdc;
	PAINTSTRUCT ps;
	HBRUSH brush;
	switch (message)
	{
	case WM_CLOSE:
		PostQuitMessage(0);
		break;
	case WM_KEYDOWN:
		/*if(wPAREAM == 65)
		{
		MessageBox(hwnd,"想要生活过得去，不怕身上背的绿","忍者神龟",MB_ABORTRETRYIGNORE  );
		}*/

		hdc = GetDC(hwnd);
		brush = CreateSolidBrush(RGB(255,0,0));
		SelectObject(hdc,brush);
		Ellipse( hdc,130,130,270,270);
		ReleaseDC(hwnd,hdc);

		break;
	case WM_LBUTTONDOWN:
		x = LOWORD (lPARAM);
		y = HIWORD (lPARAM) ;
		/*	MessageBox(hwnd,"想要生活过得去，不怕身上背的绿","忍者神龟",MB_ABORTRETRYIGNORE  );*/

		/*sprintf(str,"%d,%d",x,y);
		MessageBox(hwnd,str,"忍者神龟",MB_ABORTRETRYIGNORE);*/

		hdc = GetDC(hwnd);
		Ellipse( hdc,x-25,y-25,x+25,y+25);
		ReleaseDC(hwnd,hdc);

		break;
	case WM_PAINT:
		hdc = BeginPaint(hwnd,&ps);
		Rectangle(hdc,100,100,300,300);
		EndPaint(hwnd,&ps);
		break;
	case WM_TIMER:
		MessageBox(hwnd,"你是*","你真聪明",MB_OK );
		
		

		break;
	}
	return DefWindowProc(hwnd,message,wPAREAM,lPARAM);
}