QT menu bar, toolbar and status bar

Prior to 《 Add action 》 In the article , We already know ,Qt Abstract the elements of user interface interaction into a “ action ”, Use QAction Class represents .QAction Can be added to the menu 、 On the toolbar . period , We also introduced some details , For example, the use of resource files 、 Object model and layout manager . This section is about the menu bar 、 Toolbar and status bar .

Let's assume that the window is still built on QMainWindow Class , This will make our development much simpler . Of course , In the actual development process ,QMainWindow Usually only as “ main window ”, Dialog windows are used more QDialog class . We'll see in the back ,QDialog Classes will be missing QMainWindow Class provides convenient functions , such as menuBar() as well as toolBar().

Let's go back to 《 Add action 》 Code snippet in article ：

openAction = new QAction(QIcon(":/images/doc-open"), tr("&Open..."), this);
openAction->setShortcuts(QKeySequence::Open);
openAction->setStatusTip(tr("Open an existing file"));
connect(openAction, &QAction::triggered, this, MainWindow::open);
 
QMenu *file = menuBar()->addMenu(tr("&File"));
file->addAction(openAction);
 
QToolBar *toolBar = addToolBar(tr("&File"));
toolBar->addAction(openAction);

We see , Use menuBar() function ,Qt Created a menu bar for us .menuBar() yes QMainWindow Provided function , So you won't be QWidget perhaps QDialog It's found in . This function will return to the menu bar of the window , If there is no menu bar, a new one will be created . That explains , Why can we directly use menuBar() The return value of the function , After all, we didn't create a menu bar object ！ original , This is it. menuBar() Created and returned for us .

Qt in , The class representing the menu is QMenuBar（ You should have thought of the name ）.QMenuBar It represents the menu bar at the top of the window . We use it addMenu() Function to add a menu . Although we only provide a string as a parameter , however Qt To display it as the text of the newly created menu . as for & Symbol , We have explained , This can create a shortcut key for the menu . When we create the menu object , You can put the QAction Add to this menu , That is to say addAction() Function function .

Below QToolBar Part is very similar . seeing the name of a thing one thinks of its function ,QToolBar Toolbar . We use addToolBar() Function to add a new toolbar . Why is the first one menuBar() And now it's addToolBar() Well ？ Because a window has only one menu bar , But there may be multiple toolbars . If we change the code ：

QToolBar *toolBar = addToolBar(tr("&File"));
toolBar->addAction(openAction);
 
QToolBar *toolBar2 = addToolBar(tr("Tool Bar 2"));
toolBar2->addAction(openAction);

We see , Now there are two toolbars ：

Toolbars can be set to fixed 、 Floating, etc , For specific settings, please refer to Qt file .

We said earlier , Use QAction::setStatusTip() You can set the prompt text of this action on the status bar . But now we put the mouse on the button , You can't see the prompt text . The reason is simple , We didn't add a status bar . How to add ？ Similar to the previous QMainWindow::menuBar(),QMainWindow There is one statusBar() function . Let's add this function ：

QToolBar *toolBar2 = addToolBar(tr("Tool Bar 2"));
toolBar2->addAction(openAction);
 
statusBar();

Then compile and run ：

We added a lonely statuBar() It's quite different , however , Same as the one in front menuBar() Similar implementation of , This function returns a QStatusBar object , If not, create it first and then return .

QStatusBar Inherited QWidget, therefore , We can put any other QWidget Add subclasses to the status bar , To achieve something similar Photoshop There is a proportional display at the bottom of the window 、 Complex status bar with grid switches . of QStatusBar For more information , Please refer to Qt file .

For those without these functions QDialog perhaps QWidget How to do it? ？ Remember to ,QToolBar as well as QStatusBar All are QWidget Subclasses of , So we can add it in combination with the layout manager to another QWidget above .QLayout The layout provides setMenuBar() function , You can easily add a menu bar . See the document for details .

thus , We have already introduced the elements that make up the window . Combine these elements with layout management , We should be able to implement a simple general window . When we finish the window layout , We can consider adding functions to it . This is the content of our later chapters .