Two-way Button Example | Qt Widgets 5.14.0

Qt 5.14 | Qt Widgets | Two-way Button Example

Qt 5.14.0 Reference Documentation

# Two-way Button Example

The Two-way button example shows how to use The State Machine Framework to implement a simple state machine that toggles the current state when a button is clicked.

      int main(int argc, char **argv)
      {
          QApplication app(argc, argv);
          QPushButton button;
          QStateMachine machine;

The application's main() function begins by constructing the application object, a button and a state machine.

          QState *off = new QState();
          off->assignProperty(&button, "text", "Off");
          off->setObjectName("off");

          QState *on = new QState();
          on->setObjectName("on");
          on->assignProperty(&button, "text", "On");

The state machine has two states; `on` and `off`. When either state is entered, the text of the button will be set accordingly.

          off->addTransition(&button, &QAbstractButton::clicked, on);
          on->addTransition(&button, &QAbstractButton::clicked, off);

When the state machine is in the `off` state and the button is clicked, it will transition to the `on` state; when the state machine is in the `on` state and the button is clicked, it will transition to the `off` state.

          machine.addState(off);
          machine.addState(on);

The states are added to the state machine; they become top-level (sibling) states.

          machine.setInitialState(off);
          machine.start();

The initial state is `off`; this is the state the state machine will immediately transition to once the state machine is started.

          button.resize(100, 50);
          button.show();
          return app.exec();
      }

Finally, the button is resized and made visible, and the application event loop is entered.

Example project @ code.qt.io