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  1. 27th March 2019, 16:02 #1
    MongKong
    MongKong is offline Novice
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    Unhappy Program crashes when Canon ball reaches "water"

    So i made a simple game where i protect my island from incoming enemies and at the start u control ship and when you press space you shoot a canon ball and all goes well until my canon ball reaches the point where i delete it.
    I get a segmentation error which i believe means that im trying to reach memory that no longer exists, but still have no idea what is wrong...

    and these are the errors i get:

    error.jpg
    link: https://ddgobkiprc33d.cloudfront.net...b6759bc53e.png

    QGraphicsItem::x

    graphiitem.jpg
    link: https://ddgobkiprc33d.cloudfront.net...5b5438eff2.png

    function inside Canon Class moveCanonBall()

    mvoecanoin.jpg
    link: https://ddgobkiprc33d.cloudfront.net...92fc602e76.png

    and this

    this.jpg
    link: https://ddgobkiprc33d.cloudfront.net...e9062b1a01.png

    This is Canon's header file:
    Qt Code: 
    1. #ifndef CANON_H
    2. #define CANON_H
    3.  
    4. #include <QGraphicsItem>
    5. #include <QObject>
    6. #include <QGraphicsPathItem>
    7. #include <QTimer>
    8.  
    9. class Canon: public QObject, public QGraphicsPixmapItem{
    10.     Q_OBJECT
    11. public:
    12.     Canon(QGraphicsItem *parent=0);
    13.     ~Canon();
    14.     QTimer *time;
    15.     static bool getCanonBallGone();
    16.     static bool setCanonBallGoneToFalse();
    17.     static bool setCanonBallGoneToTrue();
    18. private:
    19.     int direction;
    20.     double xPl;
    21.     double yPl;
    22.     double newX;
    23.     double moveByX;
    24.     double moveByY;
    25.     bool moveDown;
    26.     double help;
    27.     bool ballHitEnd;
    28.     static bool CanonBallGone;
    29.     int splashLasting;
    30.  
    31. public slots:
    32.     void moveCanonBall();
    33. };
    34.  
    35. #endif // CANON_H
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    And this i canon's .cpp file:

    Qt Code: 
    1. #include "canon.h"
    2. #include "game.h"
    3. #include "math.h"
    4. #include "soundeffects.h"
    5. #include <QGraphicsPixmapItem>
    6. #include <QPixmap>
    7. #include <QObject>
    8. #include <QTimer>
    9. #include <QDebug>
    10. #include <QMediaPlayer>
    11.  
    12. #include "soundeffects.h"
    13.  
    14. extern Game *game;
    15.  
    16. bool Canon::CanonBallGone=false;
    17.  
    18. Canon::Canon(QGraphicsItem *parent): QGraphicsPixmapItem(parent){
    19.  
    20.     ballHitEnd = false;
    21.  
    22.     setPixmap(QPixmap(":/Images/Canon_1.png")); // 30x25
    23.     SoundEffects::canonBallShot(1);
    24.     game->scene->addItem(this);
    25.  
    26.     // bullet cords
    27.     moveByY = 1.0;
    28.     moveDown = false;
    29.     splashLasting = 0;
    30.  
    31.     // shrani direction katero player trenutno is facing // saves the direction which the player is currently facing
    32.     // (left==3, right ==1)
    33.     direction = game->player->getLeftOrRightDirection();
    34.     if(direction == 1){
    35.         xPl = game->player->x()+83;
    36.         yPl = game->player->y()+42;
    37.         newX = game->player->x()+83;
    38.     }else if(direction == 3){
    39.         xPl = game->player->x()-18;
    40.         yPl = game->player->y()+42;
    41.         newX = game->player->x()-18;
    42.     }
    43.  
    44.     time = new QTimer();
    45.     connect(time,SIGNAL(timeout()),this,SLOT(moveCanonBall()));
    46.     time->start(5);
    47. }
    48.  
    49. Canon::~Canon(){
    50.     delete time;
    51. }
    52.  
    53. bool Canon::getCanonBallGone(){
    54.     return CanonBallGone;
    55. }
    56.  
    57. bool Canon::setCanonBallGoneToFalse(){
    58.     CanonBallGone = false;
    59. }
    60.  
    61. bool Canon::setCanonBallGoneToTrue(){
    62.     CanonBallGone = true;
    63. }
    64.  
    65.  
    66. void Canon::moveCanonBall(){
    67.  
    68.     if(direction==1 && ballHitEnd==false){
    69.         // s pomocjo balisticne enacbe zracunamo y  // with a help of this function we calculate y  ( parabolic movement of the canon ball )
    70.         help = (0.5*(x()-xPl)*tan(0.6)-(0.5 *pow((x()-xPl),2))
    71.                 / (2*pow(20,2)*pow(cos(0.6),2))+yPl)-yPl;
    72.         moveByY = yPl - help;
    73.         setY(moveByY);
    74.         setPos(x(),y());
    75.  
    76.         // povecujemo x za 1.5  // incrementing x by 1.5
    77.         setX(x()+1.5);
    78.  
    79.         // ce je canon ball v vodi spremenimo sliko v splash sliko  // if canon ball hits its final destination we change picture to a splash 
    80.         if(y() >= yPl+32){
    81.  
    82.             ballHitEnd = true;
    83.             setPixmap(QPixmap(":/Images/Splash_1.png"));
    84.         }
    85.  
    86.     }
    87.  
    88.  
    89.     else if(direction==3 && ballHitEnd == false){
    90.  
    91.         help = (0.5*(newX-xPl)*tan(0.6)-(0.5 *pow((newX-xPl),2))
    92.                 / (2*pow(20,2)*pow(cos(0.6),2))+yPl)-yPl;
    93.         moveByY = yPl - help;
    94.         setY(moveByY);
    95.         setPos(x(),y());
    96.  
    97.         // povecujemo x za 1.5 // incrementing x by 1.5
    98.         newX = newX + 1.5;
    99.         setX(x()-1.5);
    100.  
    101.         // ce je canon ball v vodi spremenimo sliko v splash sliko // if canon ball hits its final destination we change picture to a splash
    102.         if(y() >= yPl+32){
    103.  
    104.             ballHitEnd = true;
    105.             setPixmap(QPixmap(":/Images/Splash_2.png"));
    106.         }
    107.     }
    108.  
    109.  
    110.  
    111.     // slika ostane nekaj sekund nato se canon sporsti s pomnilnika // picture stays as a splash for couple of microseconds then we delete the canon ball from memory
    112.     if(ballHitEnd == true){
    113.  
    114.         splashLasting++;
    115.  
    116.         if(splashLasting == 15){
    117.             game->scene->removeItem(this);
    118.             CanonBallGone=true;
    119.             delete this;
    120.        }
    121.     }
    122.     // ce je canon ball sou izven scene ga sporstimo iz pomnilnika // if canon ball is out of the scene we remove it  from the scene and delete it
    123.     if(x()<(0-30) || x()>game->getW()+30){
    124.         qDebug() << "deleted canonball";
    125.         game->scene->removeItem(this);
    126.         delete time;
    127.         CanonBallGone=true;
    128.         delete this;
    129.     }
    130. }
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    Last edited by MongKong; 27th March 2019 at 16:23.
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