Notes

Bullet.cpp:

#include "Bullet.h"
#include <QTimer>
#include <QGraphicsScene>
#include <QList>
#include "Enemy.h"
#include "Game.h"

extern Game * game;
Bullet::Bullet(QGraphicsItem *parent): QObject(), QGraphicsRectItem(parent){

setRect(0,0,10,50);
QTimer * timer = new QTimer(this);
connect(timer,SIGNAL(timeout()),this,SLOT(move()));

timer->start(50);
}

void Bullet::move(){

QList<QGraphicsItem *> colliding_items = collidingItems();


for (int i = 0, n = colliding_items.size(); i < n; ++i){
if (typeid(*(colliding_items[i])) == typeid(Enemy)){
game->score->increase();


scene()->removeItem(colliding_items[i]);
scene()->removeItem(this);


delete colliding_items[i];
delete this;


return;
}
}


setPos(x(),y()-10);

if (pos().y() + rect().height() < 0){
scene()->removeItem(this);
delete this;
}
}

Bullet.h:

#ifndef BULLET
#define BULLET

#include <QGraphicsRectItem>
#include <QGraphicsItem>
#include <QObject>

class Bullet: public QObject,public QGraphicsRectItem{
Q_OBJECT
public:
Bullet(QGraphicsItem * parent=0);
public slots:
void move();
};

#endif // BULLET

Enemy.cpp:

#include "Enemy.h"
#include <QTimer>
#include <QGraphicsScene>
#include <QList>
#include <stdlib.h> // rand() -> really large int
#include "Game.h"

extern Game * game;

Enemy::Enemy(QGraphicsItem *parent): QObject(), QGraphicsRectItem(parent){
int random_number = rand() % 700;
setPos(random_number,0);


setRect(0,0,100,100);


QTimer * timer = new QTimer(this);
connect(timer,SIGNAL(timeout()),this,SLOT(move()));


timer->start(50);
}

void Enemy::move(){

setPos(x(),y()+5);


if (pos().y() > 600){

game->health->decrease();

scene()->removeItem(this);
delete this;
}
}

Enemy.h:

#ifndef ENEMY
#define ENEMY

#include <QGraphicsRectItem>
#include <QObject>
#include <QGraphicsItem>

class Enemy: public QObject,public QGraphicsRectItem{
Q_OBJECT
public:
Enemy(QGraphicsItem * parent=0);
public slots:
void move();
};

#endif // ENEMY

Game.cpp:

#include "Game.h"
#include <QTimer>
#include <QGraphicsTextItem>
#include <QFont>
#include "Enemy.h"

Game::Game(QWidget *parent){

scene = new QGraphicsScene();
scene->setSceneRect(0,0,800,600); // make the scene 800x600 instead of infinity by infinity (default)


setScene(scene);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setFixedSize(800,600);


player = new Player();
player->setRect(0,0,100,100); // change the rect from 0x0 (default) to 100x100 pixels
player->setPos(400,500); // TODO generalize to always be in the middle bottom of screen

player->setFlag(QGraphicsItem::ItemIsFocusable);
player->setFocus();

scene->addItem(player);


score = new Score();
scene->addItem(score);
health = new Health();
health->setPos(health->x(),health->y()+25);
scene->addItem(health);


QTimer * timer = new QTimer();
QObject::connect(timer,SIGNAL(timeout()),player,SLOT(spawn()));
timer->start(1500);

show();
}

Game.h:
#ifndef GAME
#define GAME

#include <QGraphicsView>
#include <QWidget>
#include <QGraphicsScene>
#include "Player.h"
#include "Score.h"
#include "Health.h"

class Game: public QGraphicsView{
public:
Game(QWidget * parent=0);

QGraphicsScene * scene;
Player * player;
Score * score;
Health * health;

};

#endif // GAME

Health.cpp:

#include "Health.h"
#include <QFont>

Health::Health(QGraphicsItem *parent): QGraphicsTextItem(parent){

health = 3;


setPlainText(QString("Health: ") + QString::number(health)); // Health: 3
setDefaultTextColor(Qt::black);
setFont(QFont("times",16));
}

void Health::decrease(){
health--;
setPlainText(QString("Health: ") + QString::number(health)); // Health: 2
}

int Health::getHealth(){
return health;
}

Health.h:
#ifndef HEALTH
#define HEALTH

#include <QGraphicsTextItem>

class Health: public QGraphicsTextItem{
public:
Health(QGraphicsItem * parent=0);
void decrease();
int getHealth();
private:
int health;
};

#endif // HEALTH

Player.cpp:

#include "Player.h"
#include <QGraphicsScene>
#include <QKeyEvent>
#include "Bullet.h"
#include "Enemy.h"

Player::Player(QGraphicsItem *parent): QGraphicsRectItem(parent){

}

void Player::keyPressEvent(QKeyEvent *event){

if (event->key() == Qt::Key_Left){
if (pos().x() > 0)
setPos(x()-10,y());
}
else if (event->key() == Qt::Key_Right){
if (pos().x() + 100 < 800)
setPos(x()+10,y());
}

else if (event->key() == Qt::Key_Space){

Bullet * bullet = new Bullet();
bullet->setPos(x(),y());
scene()->addItem(bullet);
}
}

void Player::spawn(){

Enemy * enemy = new Enemy();
scene()->addItem(enemy);
}

Player.h:

#ifndef PLAYER
#define PLAYER

#include <QGraphicsRectItem>
#include <QObject>
#include <QGraphicsItem>

class Player:public QObject, public QGraphicsRectItem{
Q_OBJECT
public:
Player(QGraphicsItem * parent=0);
void keyPressEvent(QKeyEvent * event);
public slots:
void spawn();
};

#endif // PLAYER

Score.cpp:

#include "Score.h"
#include <QFont>

Score::Score(QGraphicsItem *parent): QGraphicsTextItem(parent){

score = 0;


setPlainText(QString("Score: ") + QString::number(score)); // Score: 0
setDefaultTextColor(Qt::blue);
setFont(QFont("times",16));
}

void Score::increase(){
score++;
setPlainText(QString("Score: ") + QString::number(score)); // Score: 1
}

int Score::getScore(){
return score;
}

Score.h:

#ifndef SCORE
#define SCORE

#include <QGraphicsTextItem>

class Score: public QGraphicsTextItem{
public:
Score(QGraphicsItem * parent=0);
void increase();
int getScore();
private:
int score;
};

#endif // SCORE

main.cpp:

#include <QApplication>
#include "Game.h"


Game * game;

int main(int argc, char *argv[]){
QApplication a(argc, argv);

game = new Game();
game->show();

return a.exec();
}