I'm trying to develop a file browser in Qt and C++.
Opening a FileSystem can take a lot of memory. In that way, the best is to only open what is inside a folder when I click on it.
In my browser.h, I have declared the OnClick signal.
class Browser : public QTreeWidget
{
Q_OBJECT
public:
Browser(USBDevice dev, QWidget* parent = 0);
QTreeWidget(parent)
{
connect(this , SIGNAL(itemClicked(QTreeWidgetItem*,int)),this,
// SLOT(showDirectory(QTreeWidgetItem*,int)));
};
~Browser(){};
public slots:
void showDirectory(QTreeWidgetItem* item, int /*column*/)
{
...
}
};
QTreeWidget is failing to build saying :
error: function definition does not declare parameters - QTreeWidget(parent)
in the browser.cpp, I have wrote the code to create window, widget..
Browser::Browser(USBDevice dev, QWidget *parent) :
QTreeWidget(parent)
{
QMainWindow *window = new QMainWindow();
window->setWindowTitle(QString::fromUtf8("PULS"));
window->resize(400, 400);
QWidget *centralWidget = new QWidget(window);
QTreeWidget *MyTree = new QTreeWidget(centralWidget);
MyTree->setFixedSize(395,395);
}
//Set QTreeWidget Column Header
QTreeWidgetItem* headerItem = new QTreeWidgetItem();
headerItem->setText(0,QString("File Name"));
headerItem->setText(1,QString("Size (Bytes)"));
headerItem->setText(2,QString("Date"));
MyTree->setHeaderItem(headerItem);
I don't understand but How to manage connect ?
You've got a ; instead of a : before the initialiser list for your constructor:
Browser(USBDevice dev, QWidget* parent = 0); // <--- here
QTreeWidget(parent)
{
...
FWIW, I recommend putting the colon at the start of the line like this:
Browser(USBDevice dev, QWidget* parent = 0)
: QTreeWidget(parent)
{
...
That way it's much clearer how the second line relates to the first and third, and you'll get in the habit of editing the declaration when you go to make it a definition, avoiding the kind of problem you had.
Related
Consider this QWidget initialized as:
QWidget *Logger;
Logger = new QWidget();
QPushButton *btn;
btn= new QPushButton(Logger);
btn->setObjectName(QStringLiteral("pushButton"));
Logger->show();
It display the Logger with a button with text pushButton.
Now Later if i want to access pushButton, i do it like this:
QPushButton *pushButton = Logger->findChild<QPushButton *>("pushButton");
pushButton->setText("NEW BUTTON");
I want to know is there a possibility to access directly this pushButton from Logger??Something like:
Logger->btn ...
I tried but it does not work. I have Widgets defined like this with many child objects and i wonder is this the only way to access them at run time??
EDIT: #drescherjm, So something along these lines you mean:
class MyWidget : QWidget
{
public:
QPushButton *pushButton;
MyWidget(){
pushButton = new QPushButton(this);
}
};
MyWidget *w = new MyWidget();
w->pushButton->setText("XYZ");
And is it worth it to create so many classes?? for small redundant tasks?
It won't work the way that you are expecting it to work. Use btn as long as it is in scope.
If you are creating btn somewhere locally, but your use-case demands you to use it in different places across your code, then you need to reconsider your design and make the QPushButton part of a class member.
Something of this sort :
#include <QPushButton>
class SampleWidget : public QWidget
{
public :
SampleWidget( QWidget * inParent );
// public methods to change the properties of the QPushButton go here.
void SetButtonText( QString const & inString );
bool IsButtonChecked();
private :
QPushButton *mSampleButton;
};
And in the implementation :
SampleWidget::SampleWidget(QWidget *parent)
:
mSampleButton( new QPushButton( parent ) )
{
// connect( mSampleButton,......... ); Connection to slot
}
void SampleWidget::SetButtonText( QString const & inString )
{
mSampleButton->setText( inString );
}
bool
SampleWidget::IsButtonChecked()
{
return mSampleButton->isChecked();
}
The question was not very clear on what you exactly want, but it seems like you are struggling to understand how to alter the attributes of a push button if it is a private member of a class and the above example will help you with that.
I have a QDockWidget class and a QMainWindow:
// docker.hpp
class Docker : public QDockWidget
{
Q_OBJECT
public:
Docker(QString title, QWidget* parent = 0);
}
// docker.cpp
Docker::Docker(QString title, QWidget* parent): QDockWidget(title, parent)
{
QWidget* widget = new QWidget(this);
widget.setMinimumSize(200, 200);
setWidget(widget);
widget->setStyleSheet("border:5px solid gray;");
setAllowedAreas(Qt::AllDockWidgetAreas);
}
// mainwindow.hpp
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget* parent);
private slots:
void createDockers();
};
// mainwindow.cpp
MainWindow::MainWindow(QWidget* parent): QMainWindow(parent)
{
setDockOptions(dockOptions() |
QMainWindow::AllowTabbedDocks |
QMainWindow::GroupedDragging);
// The following line of code does not change the situation.
// setTabPosition(Qt::RightDockWidgetArea, QTabWidget::East);
// There are some other codes which connect a button to the void createDockers() method
}
void createDockers()
{
Docker* dock = new Docker("Docker", this);
dock->setFloating(true);
dock->show();
}
I am able to create two Dockers with clicks of the button mentioned above.
However, when I drag one QDockWidget onto the other, the border disappears and no tabs show up:
I am expecting the following to happen: (Achieved by spawning several QDockWidgets)
I am also noticing that one of the QDockWidgets did not vanish. Instead, it merged back to the MainWindow. This only happens if they are the "first two" QDockWidgets.
What caused this problem and how to solve it? I am trying to mimic this project.
I guess it's linked to the QMainWindow::GroupedDragging option. I'm pretty sure it should work well without it (I mean for the not showing tab issue). Do you have restrictions on dock position somewhere else? The documentation implies it could create issues: http://doc.qt.io/qt-5/qmainwindow.html#DockOption-enum
For the style issue, you may need to redefine it on tab event, because once tabbed, the widget may inherit the tab style instead of the dock widget style you defined (not certified at all ^^)
Last guess/thing you can try, is to start with the dock tabbed and not floating to see if you have any new bahaviour, it was what I was doing in a previous project and it was working pretty well.
Sorry but no other ideas for the moment.
I am currently writing a C++ Application using the Qt framework, in which the 'main window' inherits from the QWidget class:
class Draughts : public QWidget
{
Q_OBJECT
public:
explicit Draughts(QWidget *parent = 0);
~Draughts();
private:
Ui::Draughts *ui;
};
And I attempted to add a simple menu bar to the application, using the following code:
Draughts::Draughts(QWidget *parent) :
QWidget(parent),
ui(new Ui::Draughts)
{
ui->setupUi(this);
QWidget *menuWidget = new QWidget;
QMenu *menuGame = new QMenu("Game");
menuGame->addAction("New");
menuGame->addAction("Exit");
QMenu *menuHelp = new QMenu("Help");
menuHelp->addAction("How to Play...");
menuHelp->addAction("About");
//Setup the Application Menu
QMenuBar mainMenu(this);
mainMenu.addMenu(menuGame);
mainMenu.addMenu(menuHelp);
}
Should I be using the QMainWindow class instead of the QWidget class for my application?
It would be easier to use QMainWindow, because it provides a convenient menuBar() method:
QMenuBar* mainMenu = this->menuBar();
But it is possible to add it to QWidget, just as any other widget. Just don't allocate it in the local scope, because it will be deleted after the function finishes. Instead, do it like with other widgets:
QMenuBar mainMenu = new QMenuBar(this);
You should also probably add a layout to your widget, and add the menu to the layout to have more control over where does it appear. You may find this tutorial useful.
(Note: I started learning Qt yesterday and I did my search before asking this.)
After a bit of playing with Qt Designer I decided to make a more serious program, all programatically. Whereas before, simple taskes seemed.. simple, now, diaplaying a button is hell of a complicated because it doesn't show up.
main.cpp
int main(int argc, char * argv[])
{
QApplication app(argc, argv);
PixelPeep p;
p.show();
return app.exec();
}
pixelpeep.h - relevant part
class PixelPeep : public QMainWindow
{
Q_OBJECT
public:
explicit PixelPeep(QWidget *parent = 0);
signals:
public slots:
private:
QToolBar * toolBar;
QHBoxLayout * toolbarLayout;
QToolButton * addButton; // add new image
QScrollBar * zoomBar;
};
pixelpeep.cpp - relevant part
PixelPeep::PixelPeep(QWidget *parent) :
QMainWindow(parent)
{
resize(600,375);
toolBar = new QToolBar;
addButton = new QToolButton;
addButton->setGeometry(20,20,20,20);
toolBar->addWidget(addButton);
toolbarLayout = new QHBoxLayout;
toolbarLayout->addWidget(addButton);
}
After all this, I get an empty window.
Possible cause, AFAIK:
button would go out of scope after being created in the class constructor - it's not the case here because it's dynamically allocated and pointer by the private member addButton
not being in a layout or having size 0 - it's not the case since both of these were addressed in the code
What else could it be?
Sorry for such a noob question...
Call addToolBar(toolBar); inside the PixelPeep constructor.
You didn't set any icon on your button so it will appear as invisible. Hover over it and you will see it's there:
In Qt Creator, I have a couple of widgets declared like so:
Header File:
class MapViewer : public QGraphicsView
{
Q_OBJECT
public:
explicit MapViewer(QGraphicsScene *scene, QWidget *parent = 0);
~MapViewer();
public slots:
void mousePressEvent(QMouseEvent *event);
};
// Declaration for the map editor window.
class MapEditor : public QMainWindow
{
Q_OBJECT
public:
explicit MapEditor(QWidget *parent = 0);
~MapEditor();
public:
QLayout *editorLayout;
QPushButton *btn;
QGraphicsScene *mapScene;
MapViewer *mapView;
private:
Ui::MapEditor *ui;
};
CPP File:
MapEditor::MapEditor(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MapEditor)
{
ui->setupUi(this);
this->setWindowTitle("2DXY :: Map Editor");
this->setGeometry(10,10,1170,750);
editorLayout = new QVBoxLayout; // Create a new layout
this->setLayout(editorLayout); // Set the widget's layout to our newly created layout.
mapScene = new QGraphicsScene(); // Create a new graphics scene to draw upon.
mapView = new MapViewer(mapScene,this); // Create a new graphics view to display our scene - set its parent to 'this' so that it doesn't open in a new window.
mapView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
mapView->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
mapView->setGeometry(20,20,1178,546); // Width first, then height.
AND:
void MapViewer::mousePressEvent(QMouseEvent *event)
{
// Show an empty message box, just to check that the event handler works!
QMessageBox *notification = new QMessageBox();
notification->show();
notification->exec();
// Some how access the same QGraphicsScene and View (mapScene, mapView) as above, so
// I can update their contents on the open form / window.
}
And as you can see, I wish to access the Graphics Scene again to update it, then redraw it (or whatever). But I'm not able to access the graphics scene at all, despite a few hours of trial and error with declaring widgets in different ways.
I know that the listener itself works, because if it's set to open a new message box, or output to the debug window, then it works, it's just that I can't access the widgets I've already defined.
I feel that there is a (relatively) easy solution to this problem, and that I'm just missing something obvious.
You passed the QGraphicsScene to your MapRender object's constructor. What do you do with the scene within its constructor? Ideally, you should be storing it as a data member of MapRender. For example:
class MapRender {
public:
MapRender(QGraphicsScene* scene)
: scene_(scene)
{
}
public slots:
void mousePressEvent(QMouseEvent *event);
private:
QGraphicsScene* scene_;
}
Now in your implementation of mousePressEvent, you can access to the scene member:
void MapRender::mousePressEvent(QMouseEvent *event) {
int CursorX = event->globalX();
int CursorY = event->globalY();
QGraphicsRectItem *clickedBox = new QGraphicsRectItem(40,40,32,32);
clickedBox->setBrush(QBrush(Qt::blue));
scene_->addItem(clickedBox);
}
Keep in mind you should ideally be putting the implementation of the constructor in your cpp file, but my example does it in the declaration for brevity.
void MapViewer::mousePressEvent(QMouseEvent *event)
{
// Show an empty message box, just to check that the event handler works!
QMessageBox *notification = new QMessageBox();
notification->show();
notification->exec();
// To add something whenever the user clicks, you don't need the view,
// just the scene.
scene()->addItem( new MyItem() );
}
Remember MapViewer derives from QGraphicsView and the view must know about the scene it belongs to - so it has a scene() method to return it, which you inherited.