Exception thrown at 0x0131EB06 Visual Studio

Question

Im quite new at Directx, and I wanted to test a simple direct2d application that draws a circle in a window. I am using Visual Studio Professional. When ever I run my program called D2D Test Engine with Local Windows Debugger, i get these errors:

Exception thrown at 0x0140EB06 in D2D Test Engine.exe: 0xC0000005: Access violation reading location 0x00000008.
Exception thrown at 0x0140EB06 in D2D Test Engine.exe: 0xC0000005: Access violation reading location 0x00000008.
Exception thrown at 0x0140EB06 in D2D Test Engine.exe: 0xC0000005: Access violation reading location 0x00000008.

I can't figure out what is wrong with my program. Here is my code:

#include <Windows.h>
#include "Graphics.h"
Graphics* graphics;
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
if (uMsg == WM_DESTROY) {
    PostQuitMessage(0);
    return 0;
}
graphics->BeginDraw();
graphics->ClearScreen(0.0f, 0.0f, 0.5f);
graphics->DrawShape(100, 100, 50, 1.0f, 0.0, 0.0, 1.0);
graphics->EndDraw();
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE prevInstance, LPWSTR cmd, int nCmdShow) {
WNDCLASSEX windowclass;
ZeroMemory(&windowclass, sizeof(WNDCLASSEX));
windowclass.cbSize = sizeof(WNDCLASSEX);
windowclass.hbrBackground = (HBRUSH) COLOR_WINDOW;
windowclass.hInstance = hInstance;
windowclass.lpfnWndProc = WindowProc;
windowclass.lpszClassName = "MainWindow";
windowclass.style = CS_HREDRAW | CS_VREDRAW;
RegisterClassEx(&windowclass);
RECT rect = { 0, 0, 800, 600 };
AdjustWindowRectEx(&rect, WS_EX_OVERLAPPEDWINDOW, false, WS_EX_OVERLAPPEDWINDOW);
HWND windowHandle = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW, "MainWindow", "D2D Test Engine", WS_OVERLAPPEDWINDOW, 0, 0, rect.right - rect.left,      rect.bottom - rect.top, NULL, NULL, hInstance, 0);
    if (!windowHandle) {
        return -1;
    }
    graphics = new Graphics();
    if (graphics->Init(windowHandle) == false) {
        delete graphics;
        return -1;
    }
    ShowWindow(windowHandle, nCmdShow);
    MSG message;
    while (GetMessage(&message, NULL, 0, 0)) {
        DispatchMessage(&message);
    }
    return 0;
}

next file:

#pragma once
#include <Windows.h>
#include <d2d1.h>
class Graphics
{
ID2D1Factory* factory;
ID2D1HwndRenderTarget* renderTarget;
public:
Graphics();
virtual ~Graphics();
bool Init(HWND windowHandle);
void BeginDraw() {renderTarget->BeginDraw();}
void EndDraw() {renderTarget->EndDraw();}
void ClearScreen(float r, float g, float b);
void DrawShape(float x, float y, float radius, float r, float g, float b, float a);
};

next file:

#include "Graphics.h"
#include <d2d1.h>
#include <Windows.h>
Graphics::Graphics()
{
factory = NULL;
renderTarget = NULL;
}
Graphics::~Graphics()
{
if (factory) {
    factory->Release();
}
if (renderTarget) {
    renderTarget->Release();
}
}
bool Graphics::Init(HWND windowHandle) {
HRESULT res = D2D1CreateFactory(D2D1_FACTORY_TYPE_MULTI_THREADED, &factory);
if (res != S_OK) {
    return false;
}
RECT rect;
GetClientRect(windowHandle, &rect);
res = factory->CreateHwndRenderTarget(D2D1::RenderTargetProperties(), D2D1::HwndRenderTargetProperties(windowHandle, D2D1::SizeU(rect.right, rect.bottom)), &renderTarget);
if (res != S_OK) {
    return false;
}
return true;
}
void Graphics::ClearScreen(float r, float g, float b) {
renderTarget->Clear(D2D1::ColorF(r, g, b));
}
void Graphics::DrawShape(float x, float y, float radius, float r, float g, float b, float a) {
ID2D1SolidColorBrush* brush;

renderTarget->CreateSolidColorBrush(D2D1::ColorF(r, g, b, a), &brush);
renderTarget->DrawEllipse(D2D1::Ellipse(D2D1::Point2F(x, y), radius, radius), brush, 3.0f);
brush->Release();
}

When i dont call BeginDraw(), ClearScreen, DrawShape, and EndDraw a window comes up and it runs fine, so i think it has to do with them.

Answer 1

I figured out the answer. I am pretty new at this directx stuff, and i was using a tutorial to build this. what I needed to do was put all the functions i was calling in a if statement. here is what i did:

if (uMsg == WM_PAINT) {
    graphics->BeginDraw();
    graphics->ClearScreen(0.0f, 0.0f, 0.5f);
    graphics->DrawShape(100, 100, 50, 1.0f, 0.0, 0.0, 1.0);
    graphics->EndDraw();
}

sorry for all the trouble, im new to this.

Answer 2

Seems, that you have problem with WM_CREATE message. This message is send when CreateWindowEx called.

Graphics* graphics = NULL; // it's better to zero pointer in C++.

Simple solution - set graphics to null and check it in WindowProc function.

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    if (uMsg == WM_DESTROY) {
      PostQuitMessage(0);
      return 0;
   } 

   if (graphics) {
     graphics->BeginDraw();
     graphics->ClearScreen(0.0f, 0.0f, 0.5f);
     graphics->DrawShape(100, 100, 50, 1.0f, 0.0, 0.0, 1.0);
     graphics->EndDraw();
   }
   return DefWindowProc(hwnd, msg, wParam, lParam);
}