C++ Qt Game Tutorial 5 - Adding Enemies

给游戏新增加敌人，利用cllidingItem()方法表示两个物体是否相交。

#-------------------------------------------------
#
# Project created by QtCreator 2017-01-19T23:17:02
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = tutorial5
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0


SOURCES += main.cpp \
    myrect.cpp \
    bullet.cpp \
    enemy.cpp

HEADERS  += \
    myrect.h \
    bullet.h \
    enemy.h

#ifndef BULLET_H
#define BULLET_H

#include <QGraphicsRectItem>
#include <QObject>
class Bullet : public QObject, public QGraphicsRectItem {
    Q_OBJECT
public:
    Bullet();
public slots:
    void move();
};

#endif // BULLET_H

#ifndef ENEMY_H
#define ENEMY_H

#include <QGraphicsRectItem>
#include <QObject>
class Enemy : public QObject, public QGraphicsRectItem {
    Q_OBJECT
public :
    Enemy();
public slots:
    void move();
};

#endif // ENEMY_H

#ifndef MYRECT_H
#define MYRECT_H

#include <QGraphicsRectItem>
#include <QObject>

class MyRect : public QObject, public QGraphicsRectItem {
    Q_OBJECT
public:
    void keyPressEvent(QKeyEvent *event);
public slots:
    void spawn();
};

#endif // MYRECT_H

#include "bullet.h"
#include <QTimer>
#include <QGraphicsScene>
#include <QList>
#include "enemy.h"
#include <typeinfo>
Bullet::Bullet() : QObject(), QGraphicsRectItem()
{
    // draw the rect
    setRect(0, 0, 10, 50);

    // connect
    QTimer *timer = new QTimer(this);

    connect(timer, SIGNAL(timeout()),this, SLOT(move()));

    timer->start(50);
}

void Bullet::move()
{
    // if bullet collides with enemy, destroy both
    QList<QGraphicsItem *> colliding_items = collidingItems();
    for (int i = 0, n = colliding_items.size(); i < n; ++i) {
        if (typeid(*(colliding_items[i])) == typeid(Enemy)) {
            // remove them both
            scene()->removeItem(colliding_items[i]);
            scene()->removeItem(this);

            // delete them both
            delete colliding_items[i];
            delete this;
            return ;
        }
    }
    // move bullet up
    setPos(x(), y() - 10);
    if (pos().y() + rect().height() < 0) {
        scene()->removeItem(this);
        delete this;
    }
}

#include "enemy.h"
#include <QTimer>
#include <QGraphicsScene>
#include <QList>
#include <stdlib.h>

#include <QDebug>

Enemy::Enemy() : QObject(), QGraphicsRectItem()  {
    // set random position
    int random_number = rand() % 700;
    setPos(random_number, 0);

    //draw the rect
    setRect(0, 0, 100, 100);

    // connect
    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(move()));
    timer->start(50);
}

void Enemy::move() {
    // move enmey down
    setPos(x(), y() + 5);
    if (pos().y() + rect().height() < 0) {
        scene()->removeItem(this);
        delete this;
    }
}

#include "myrect.h"
#include <QGraphicsScene>
#include <QKeyEvent>
#include "enemy.h"
#include "bullet.h"
#include <QDebug>

void MyRect::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 MyRect::spawn() {
    // create an enemy
    Enemy *enemy = new Enemy();
    scene()->addItem(enemy);
}

#include <QApplication>
#include "myrect.h"
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QTimer>

/*
 * tutorial topics:
 * collidingItems()
 * QTimer and coordinate systems
 */

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

    // create a scene
    QGraphicsScene *scene = new QGraphicsScene();

    // create an item to add to the scene
    MyRect *player = new MyRect();
    player->setRect(0, 0, 100, 100);

    // add the item to the scene
    scene->addItem(player);

    // make rect focusable
    player->setFlag(QGraphicsItem::ItemIsFocusable);
    player->setFocus();

    // create a view to visualize the scene
    QGraphicsView *view = new QGraphicsView(scene);
    view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);

     // show the view
    view->show();
    view->setFixedSize(800, 600);
    scene->setSceneRect(0, 0, 800, 600);

    player->setPos(view->width()/2,
                             view->height() - player->rect().height());

    // spawn enemies
    QTimer *timer = new QTimer();
    QObject::connect(timer, SIGNAL(timeout()), player, SLOT(spawn()));
    timer->start(2000);
    return a.exec();
}