QActions, QToolbars, and QActionGroups

The Command pattern, as described in [Gamma95] encapsulates operations as objects with a common execution interface. This can make it possible to place operations in a queue, log operations, and undo the results of an already executed operation.

[ . . . . ] class Study : public QMainWindow { Q_OBJECT public: Study(); public slots: void actionEvent(QAction* act); private: QActionGroup* actionGroup; <-- 1 QToolBar *toolbar; <-- 2 QAction *useTheForce; QAction *useTheDarkSide; QAction *studyWithObiWan; QAction *studyWithYoda; QAction *studyWithEmperor; QAction *fightYoda; QAction *fightDarthVader; QAction *fightObiWan; QAction *fightEmperor; protected: QAction* addChoice(QString name, QString text); }; [ . . . . ]  

(1)for catching the signals

(2)for displaying the actions as buttons

[ . . . . ] Study::Study() { actionGroup = new QActionGroup(this); actionGroup->setExclusive(false); statusBar(); QWidget::setWindowTitle( "to become a jedi, you wish?" ); <-- 1 QMenu* useMenu = new QMenu("&Use", this); QMenu* studyMenu = new QMenu("&Study", this); QMenu* fightMenu = new QMenu("&Fight", this); useTheForce = addChoice("useTheForce", "Use The &Force"); useTheForce->setStatusTip("This is the start of a journey..."); useTheForce->setEnabled(true); useMenu->addAction(useTheForce); <-- 2 [ . . . . ] studyWithObiWan = addChoice("studyWithObiWan", "&Study With Obi Wan"); studyMenu->addAction(studyWithObiWan); studyWithObiWan->setStatusTip("He will certainly open doors for you..."); fightObiWan = addChoice("fightObiWan", "Fight &Obi Wan"); fightMenu->addAction(fightObiWan); fightObiWan->setStatusTip( "You'll learn some tricks from him that way, for sure!"); [ . . . . ] QMainWindow::menuBar()->addMenu(useMenu); QMainWindow::menuBar()->addMenu(studyMenu); QMainWindow::menuBar()->addMenu(fightMenu); toolbar = new QToolBar("Choice ToolBar", this); <-- 3 toolbar->addActions(actionGroup->actions()); QMainWindow::addToolBar(Qt::LeftToolBarArea, toolbar); QObject::connect(actionGroup, SIGNAL(triggered(QAction*)), this, SLOT(actionEvent(QAction*))); <-- 4 QWidget::move(300, 300); QWidget::resize(300, 300); }  

(1)The ClassName:: prefixes we use in methods here are not necessary, because the methods can be called on "this". We list the classname only to show the human reader from which class the method was inherited.

(2)It's already in a QActionGroup, but we also add it to a QMenu.

(3)This gives us visible buttons in a dockable widget for each of the QActions.

(4)Instead of connecting each individual action's signal, we perform one connect to an actionGroup that contains them all.

[ . . . . ] // Factory method for creating QActions initialized in a uniform way QAction* Study::addChoice(QString name, QString text) { QAction* retval = new QAction(text, this); retval->setObjectName(name); retval->setEnabled(false); retval->setCheckable(true); actionGroup->addAction(retval); <-- 1 return retval; }  

(1)Add every action we create to a QActionGroup so that we only connect one signal to a slot.

[ . . . . ] void Study::actionEvent(QAction* act) { QString name = act->objectName(); QString msg = QString(); if (act == useTheForce ) { studyWithObiWan->setEnabled(true); fightObiWan->setEnabled(true); useTheDarkSide->setEnabled(true); } if (act == useTheDarkSide) { studyWithYoda->setEnabled(false); fightYoda->setEnabled(true); studyWithEmperor->setEnabled(true); fightEmperor->setEnabled(true); fightDarthVader->setEnabled(true); } if (act == studyWithObiWan) { fightObiWan->setEnabled(true); fightDarthVader->setEnabled(true); studyWithYoda->setEnabled(true); } [ . . . . ] if (act == fightObiWan ) { if (studyWithEmperor->isChecked()) { msg = "You are victorious!"; } else { msg = "You lose."; act->setChecked(false); studyWithYoda->setEnabled(false); } } [ . . . . ] if (msg != QString()) { QMessageBox::information(this, "Result", msg, "ok"); } }

[ . . . .] int main( int argc, char ** argv ) { QApplication a( argc, argv ); Study study; study.show(); return a.exec(); }

(Discussion question) There are QActions as children of QWidgets all over the place. How do you gather them all for a ShortcutView widget that lets the user display and change all of the keyboard shortcuts in the application?

Revisit the 15 puzzle application in Section 11.5.2 and add QActions for:

• Shuffle puzzle
• Reset puzzle
• Quit

For Quit, pop up a message box asking whether the user is sure before actually quitting.

Write a "login" application using QMainWindow. Start with these QActions:

• Login
• Create New User
• Edit Preferences
• Change Password

These choices should be available by pull-down menu as well as toolbar. Create QActions and a QActionGroup for them all.

The last two choices should be disabled unless the user is logged in.

The initial login screen should have QLineEdits for a user id and a password. If the user chooses "Create New User" or "Change Password", the program should display a new form with QLineEdits. It should ask for the password twice, and make sure the passwords match, before actually performing the operation. If the passwords mismatch, try again.

For "Login", it should check that the user exists and that the password is valid, before letting you log in, and enabling the other QActions.

If the user chooses "Edit Preferences" it should ask the following questions:

• What is your name?
• What is your quest?
• What is your favorite color? (Use a QComboBox with preset colors to red, green, blue, black, pink, and chartreuse to choose from.)

It should remember these for each user from previous sessions.

The program should load the user data from a file called "users.xml" on startup and save to the same file when finished, without any interaction. Load and save in any format you want, using QTextStream and QFile.