c++ - 无法启动状态和状态之间的转换 : receiving various errors

Question

我在使用 Qt State Machine. 时遇到了一些问题我永远无法执行这些状态:我遇到各种类型的错误，但我无法弄清楚问题出在哪里。有关错误和导致这些错误的代码的更多信息，请参阅下文。

这是我的主要功能:

int main(int argc, char *argv[])
{
    // Initialize the app
    // ... app initialization here
    QApplication app(argc, argv);

    // Create the state machine
    QStateMachine machine;

    MyState* ms1 = new MyState("ms1");
    MyState* ms2 = new MyState("ms2");
    QFinalState* fs = new QFinalState();

    ms1->addTransition(ms2);
    ms2->addTransition(fs);

    machine.addState(ms1);
    machine.addState(ms2);
    machine.addState(fs);
    machine.setInitialState(ms1);

    QObject::connect(&machine, SIGNAL(finished()), new Finisher(), SLOT(OnFinished()));
    machine.start();
    return app.exec();
}

我在 MyState 中设置了断点，但是断点永远不会被击中并且 start/stop 方法永远不会执行(我实际上只期望 start 被调用)。应用程序直接进入 Finisher::OnFinished 方法。

这是我的州级:

class MyState: public QState
{
    Q_OBJECT
private:
    QString _stateName;
public:
    MyState(QString stateName, QState * parent = 0):QState(parent), _stateName(stateName){}
    ~MyState(){}

public slots:
    void start()
    {
        qDebug() << _stateName << " start.";
        emit finished();
    }

    void stop()
    {
        qDebug() << _stateName << " stop.";
    }

signals:
    void finished();
    //void exited();
};

Finisher 非常简单:

class Finisher:public QObject
{
    Q_OBJECT
    public slots:
    void OnFinished()
    {
        qDebug() << "Finished!";
        QTimer::singleShot(0, QApplication::instance(), SLOT(quit()));
    }
};

我尝试了几种方法，包括直接设置每个状态的父级:

// If I use the following code, I get an error 
// stating that "the state has already been added to this machine"
MyState* ms1 = new MyState("ms1");
MyState* ms2 = new MyState("ms2", ms1);
QFinalState* fs = new QFinalState(ms2);

ms1->addTransition(ms2);
ms2->addTransition(fs);

machine.addState(ms1);
machine.addState(ms2);
machine.addState(fs);
machine.setInitialState(ms1);
// .. and so on

但是，当调用 machine.addState 时似乎无法添加状态:

QStateMachine::addState: state has already been added to this machine
QStateMachine::addState: state has already been added to this machine
Unrecoverable error detected in running state machine: Missing initial state in
compound state ''

我也试过只留下构造函数而不调用 machine.addState:

QStateMachine machine;
MyState* ms1 = new MyState("ms1");
MyState* ms2 = new MyState("ms2", ms1);
QFinalState* fs = new QFinalState(ms2);

ms1->addTransition(ms2);
ms2->addTransition(fs);
machine.setInitialState(ms1);
// .. and so on

但是，在这种情况下，我得到以下错误:

QState::setInitialState: state 0xa05e5e0 is not a child of this state (0x43fe94)

QStateMachine::start: No initial state set for machine. Refusing to start.

最后一个很奇怪，因为我明确地将初始状态声明为ms1，然后调用start，所以我不知道那里有什么问题。有人对如何使这个示例起作用有任何想法吗？

Answer 1

QState 中没有类似start() 槽的东西——但它存在于QStateMachine 中。

我想你想重新实现

virtual void    onEntry ( QEvent * event )
virtual void    onExit ( QEvent * event )

方法:

class MyState: public QState
{
    Q_OBJECT
private:
    QString _stateName;
public:
    MyState(QString stateName, QState * parent = 0):QState(parent), _stateName(stateName){}
    ~MyState(){}

protected:
   virtual  void onEntry(QEvent * event)
    {
        qDebug() << _stateName << " start.";
    }

   virtual  void onExit(QEvent * event)
    {
        qDebug() << _stateName << " stop.";
    }
signals:
    void finished();
    //void exited();
};

工作正常。