Question

当我执行这个Qtimer时，它说“在非成员函数中无效使用'this'”

QTimer *timerStart( )
{
QTimer* timer = new QTimer(  );
Ball *b = new Ball();

QObject::connect(timer,SIGNAL(timeout()),b,SLOT(move()));
//timer->start( timeMillisecond );
timer->start(15);
return timer;
}

我的ball.h文件

class Ball: public QObject, public QGraphicsRectItem{
Q_OBJECT
public:
// constructors
Ball(QGraphicsItem* parent=NULL);

// public methods
double getCenterX();




public slots:
// public slots
void move();



private:
// private attributes
double xVelocity;
double yVelocity;
int counter = 0;
QTimer timerStart( );



// private methods
void stop();
void resetState();
void reverseVelocityIfOutOfBounds();
void handlePaddleCollision();
void handleBlockCollision();
};

#endif // BALL_H

move（）函数属于同一个类。我想要做的是在if条件满足时停止返回的计时器。

当我在Cpp的Ball :: Ball构造函数中发出此代码时，它工作正常。球正在移动。

  QTimer* timer = new QTimer();
  timer->setInterval(4000);

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

  timer->start(15);

但是当我在Ball :: Ball构造函数之外添加Qtimer * timerStart时，iT无法正常工作

Answer 1

将QTimer声明为您班级的成员

h file：

class Ball: public QObject, public QGraphicsRectItem{
{
  Q_OBJECT

  public:
    // constructor
    Ball(QGraphicsItem* parent=Q_NULLPTR);
    // control your timer
    void start();
    void stop();
    ...
  private:
    QTimer * m_poTimer;
}

在约束器中启动计时器对象

cpp文件：

Ball::Ball(QGraphicsItem* parent) :
      QGraphicsItem(parent)
{  
  m_poTimer = new QTimer(this); // add this as a parent to control the timer resource
  m_poTimer->setInterval(4000);

  connect(m_poTimer,SIGNAL(timeout()),this,SLOT(move()));
}

void Ball::start()
{
   // start timer
   m_poTimer->start();
}

void Ball::stop()
{
   // stop timer
   m_poTimer->stop();
}

如何在有条件的情况下停止Qtimer

1 个答案: