Qt SCXML 计算器范例

计算器 使用 Qt SCXML 去实现计算器范例 presented in the SCXML Specification.

The state machine is specified in the statemachine.scxml file and compiled into the CalculatorStateMachine class. The user interface is created using Qt Widgets.

运行范例

要运行范例从 Qt Creator ，打开欢迎模式，然后选择范例从范例。更多信息，拜访构建和运行范例 .

编译状态机

We link against the Qt SCXML module by adding the following line to the .pro 文件：

QT += widgets scxml

接着，指定要编译的状态机：

STATECHARTS = ../calculator-common/statemachine.scxml

Qt SCXML 编译器 qscxmlc , is run automatically to generate statemachine.h and statemachine.cpp , and to add them to the HEADERS and SOURCES variables for compilation.

实例化状态机

We instantiate the generated CalculatorStateMachine 类在 calculator-widgets.cpp file, as follows:

#include "statemachine.h"
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    CalculatorStateMachine machine;
    MainWindow mainWindow(&machine);
    machine.start();
    mainWindow.show();
    return app.exec();
}

连接到活动特性

After instantiating the state machine, we can connect to the active properties of the states, as follows:

    connect(ui->digit0, &QAbstractButton::clicked, [this] {
        m_machine->submitEvent("DIGIT.0");
    });
    connect(ui->digit1, &QAbstractButton::clicked, [this] {
        m_machine->submitEvent("DIGIT.1");
    });
    connect(ui->digit2, &QAbstractButton::clicked, [this] {
        m_machine->submitEvent("DIGIT.2");
    });

The state machine can notify other code when events occur:

        <transition event="DISPLAY.UPDATE">
            <log label="'result'" expr="short_expr==''?res:short_expr" />
            <send event="updateDisplay">
                <param name="display" expr="short_expr==''?res:short_expr"/>
            </send>
        </transition>

We connect to the updateDisplay event to display the data passed by the events:

    m_machine->connectToEvent(QLatin1String("updateDisplay"), this, [this](const QScxmlEvent &event) {
        const QString display = event.data().toMap().value("display").toString();
        ui->display->setText(display);
    });

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