Qt SCXML 计算器范例

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

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 lines to the example's build files.

.pro when using qmake:

QT += widgets scxml

接着，指定要编译的状态机：

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

CMakeLists.txt when using cmake:

find_package(Qt6 COMPONENTS Core Gui Widgets Scxml)
target_link_libraries(calculator-widgets PUBLIC
    Qt6::Core
    Qt6::Gui
    Qt6::Scxml
    Qt6::Widgets
)

接着，指定要编译的状态机：

qt6_add_statecharts(calculator-widgets
    ../calculator-common/statemachine.scxml
)

The statechart directives STATECHARTS or qt6_add_statecharts invoke the Qt SCXML Compiler, qscxmlc , which is run automatically to generate statemachine.h and statemachine.cpp , which are then added appropriately as headers and sources for compilation.

实例化状态机

We instantiate the generated CalculatorStateMachine 类在 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();
}

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);
    });

范例工程 @ code.qt.io