Qt SCXML 計算器範例

A widget-based application that implements the Calculator example presented in the SCXML Specification.

計算器 使用 Qt SCXML 去實現計算器範例 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.

運行範例

要運行範例從 Qt Creator ，打開歡迎模式，然後選擇範例從範例。更多信息，拜訪構建和運行範例 .

編譯狀態機

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

QT += widgets scxml

接著，指定要編譯的狀態機：

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

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

實例化狀態機

We instantiate the generated CalculatorStateMachine 類在 calculator-widgets.cpp 文件，如下：

#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();
}

連接到活動特性

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);
    });

範例工程 @ code.qt.io