CODEWITHSUNDEEP
c++qtqt-creator
Suthura Sudharaka
Suthura Sudharaka

Reputation: 673

app is closing after going back to main window / c++

In my main window i used this code to open my game application

void MainWindow::on_playButton_clicked(){   
    CSpaceInwaders* pGame = new CSpaceInwaders(qApp->screens()[0]->size());
    pGame->showFullScreen();
    pGame->Run();
}

Then in there this is the run function that I called 

void CSpaceInwaders::Run(){
scene()->clear();
setCursor(Qt::BlankCursor);

m_pCannon =new CCannon(EColor::Red);
m_pCannon->setPos(m_onScreenSize.width()/2,m_onScreenSize.height()-gCannonSize.height());
m_pCannon->setFlag(QGraphicsItem::ItemIsFocusable);
m_pCannon->setFocus();
scene()->addItem(m_pCannon);

connect(m_pCannon, &CCannon::sigIncreaseScore,this,&CSpaceInwaders::onIncreaseScore);
connect(m_pCannon, &CCannon::sigDecreseScore,this,&CSpaceInwaders::onDecreseScore);

m_pPoints = new CPoints();
scene()->addItem(m_pPoints);

QTimer* pTimer = new QTimer(this);
connect(pTimer, &QTimer::timeout,this,&CSpaceInwaders::onCreateEnemy);
pTimer->start(2000);}

after the game over I want to go back to my main window. So I used this function

void CSpaceInwaders::onGameOver(){
scene()->clear();
QMessageBox msgBox;
msgBox.setText("Game.");
msgBox.setInformativeText("You got hit ! Game Over");
msgBox.setStandardButtons(QMessageBox::Ok);
int ret = msgBox.exec();
switch (ret) {
  case QMessageBox::Ok:
    close();
    MainWindow w;
    w.show();
}}

This takes me back to the main window but after few seconds it closes.

I want to know how to fix this

Note : Created using QT

Upvotes: 1

Views: 86

Answers (2)

Suthura Sudharaka
Suthura Sudharaka

Reputation: 673

Using this I solved my problem

void CSpaceInwaders::onGameOver(){
    this->close();
}

Upvotes: 0

Some programmer dude
Some programmer dude

Reputation: 409442

The problem is with the code in the case:

case QMessageBox::Ok:
    close();
    MainWindow w;
    w.show();

The problem is two-fold: First of all you can't actually define variables inside a case like that. You need to add a scope. I'm surprised the compiler doesn't yell at you for that.

The second problem (and that's causing your problem) is that the variable w is a local variable inside the switch statement. Once the statement ends so does the life-time and w and it's destructed and ceases to exist.

The solution (as far as I know) seems to be simple: Don't create and open a new main window! When you start the "space invaders" game you never close the original main window, it's should still be running in the background.

However this is a very bad way to "run" what should essentially be either a separate program or at the very least part of your normal program flow and event loop. Either extract the mini-game into its own program that you then load and execute, or don't create a separate application object and just open a normal window and let the main application event loop handle it.

Upvotes: 4

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