Access violation writing location 0x00000000. C++ / SFML game - c++

Question

I'm working on a school project using C++ and SFML 2.0, it's due for Tuesday and I've just recently run in to this problem.
I've put an arrow on where the latest Call Stack is.
These are the code parts that I suspect might have something wrong in them. I'm also very new to c++ and I know I do alot of things wrong.
This is in my Background class, it loads all my tiles, sets their position and tiletype and so on.
The GetWayPointList returns a vector of tiles to my EnemyManager class
void Background::Load(QuadTree * quadTree) {
int tempTiles[32][32] = {... Lots of 1's and 0's in here };
for(int i = 0; i < 32; i++)
{
for(int j = 0; j < 32; j++)
{
---> tile[j][i]->tileType = tempTiles[j][i];
tile[j][i]->setPosition(sf::Vector2f((float)(i*32),(float)(j*32)));
if(tile[j][i]->tileType == 1)
{
quadTree->AddObject(tile[j][i]);
}
else if(tile[j][i]->tileType == 0)
{
tile[j][i]->distanceFromStart = INT_MAX;
tile[j][i]->parent = NULL;
vector<Tile*> tempTiles;
if(tile[j+1][i]->tileType == 0)
tempTiles.push_back(tile[j+1][i]);
if(tile[j-1][i]->tileType == 0)
tempTiles.push_back(tile[j-1][i]);
if(tile[j][i+1]->tileType == 0)
tempTiles.push_back(tile[j][i+1]);
if(tile[j][i-1]->tileType == 0)
tempTiles.push_back(tile[j][i-1]);
tile[j][i]->setSuccessors(tempTiles);
tilesList->push_back(tile[j][i]);
}
}
}
}
vector<Tile*>* Background::GetWayPointList()
{
return tilesList;
}
The Call Stack itself says TileShooter v0.1.exe!Background::Load(QuadTree*quadTree) Line 68 + 0x2e bytes.
Line 68 is where the arrow is.
If you need more code / info just say.
Any points on what's possibly wrong would be greatly appriciated.
Best Regards, Fredrik W
Edit
I've edited the code some including tile[j][i] = new Tile();
void Background::Load(QuadTree * quadTree) {
int tempTiles[32][32] = {... Lots of 1's and 0's in here };
for(int i = 0; i < 32; i++)
{
for(int j = 0; j < 32; j++)
{
tile[j][i] = new Tile();
tile[j][i]->tileType = tempTiles[j][i];
tile[j][i]->setPosition(sf::Vector2f((float)(i*32),(float)(j*32)));
if(tile[j][i]->tileType == 1)
{
quadTree->AddObject(tile[j][i]);
}
else if(tile[j][i]->tileType == 0)
{
tile[j][i]->distanceFromStart = INT_MAX;
tile[j][i]->parent = NULL;
vector<Tile*> tempTiles;
----> if(tile[j+1][i]->tileType == 0)
tempTiles.push_back(tile[j+1][i]);
if(tile[j-1][i]->tileType == 0)
tempTiles.push_back(tile[j-1][i]);
if(tile[j][i+1]->tileType == 0)
tempTiles.push_back(tile[j][i+1]);
if(tile[j][i-1]->tileType == 0)
tempTiles.push_back(tile[j][i-1]);
tile[j][i]->setSuccessors(tempTiles);
tilesList->push_back(tile[j][i]);
}
}
}
}
vector<Tile*>* Background::GetWayPointList()
{
return tilesList;
}
That didn't really solve but rather moved the error downwards, I've moved my arrow on where the Call Stack has it's latest call.

Answer 1

So your tile member is defined as Tile* tile[32][32]. That's a 2D array of size 32x32 where each element is a pointer to Tile. However, they are just pointers and currently don't point anywhere in particular - accessing them is undefined behaviour (in your case, an access violation). You need to allocate the actual Tile objects:
for (int i = 0; i < 32; i++) {
for (int j = 0; j < 32; j++) {
tile[i][j] = new Tile();
}
}
Don't forget to do the same kind of loop in the destructor of Background that instead does delete tile[i][j];.
Better yet, don't dynamically allocate your tiles and just define tile as:
Tile tile[32][32];
Even better yet (!), use std::array<std::array<Tile,32>,32>. :)
To answer your edit, even though it's invalidated my above answer: You're accessing the j+1th element of tile. When j is 31, you're accessing tile[32] which is outside the bounds of your array.