I am trying to make a GUI so when you increase the "Article" count, then more of the article inputs show up. For example, if I change the Articles count to 2, I would want another group of inputs to show up for Article 2, and if the Articles count changes to three, there would be three groups of inputs, but since that would use up more space than the window has, it would begin to scroll.
I was thinking of using one of the tree, list, or table widgets, but I am not sure if that is even the right direction I am supposed to be going to. Can anyone push me in the right direction?
Here is a picture, since my description is not good.
You should put all the widgets needed for one article into one single custom widget. Whenever the spin box is changed (code in slot) you can add / remove one instance of such a custom widget to a scroll area.
Within the constructor of this custom widget class (let's call it ArticleWidget), you should define signals in your custom widget which notify about changes made in its child widgets. Connect these within your custom widget:
ArticleWidget::ArticleWidget(QWidget *parent) :
QWidget(parent)
{
ui->setupUi(this); // when you use QtDesigner to design the widget
// propagate signals from my inner widgets to myself:
connect(ui->title, SIGNAL(textChanged(QString)),
SIGNAL(titleChanged(QString)));
}
In the outer widget, whenever creating such a custom widget, connect its signals to your processing slots:
void OuterWidget::articleCountChanged(int)
{
...
if(/*increased*/)
{
ArticleWidget *article = new ArticleWidget(this);
connect(article, SIGNAL(titleChanged(QString)),
SLOT(art_titleChanged(QString)));
ui->scrollAreaViewport->layout()->addWidget(article);
}
...
}
You can access the article widget using sender():
void OuterWidget::art_titleChanged(QString)
{
ArticleWidget *articleWidget = qobject_cast<ArticleWidget*>(sender());
Q_ASSERT(articleWidget); // make sure the signal comes from an ArticleWidget
// if you want to store articles in a vector of custom types,
// you could give this type a pointer to the widget, so you can
// find the index if you have the widget pointer:
foreach(Article *article, articles)
if(article->widget == articleWidget)
article->title = title; // make some changes
}
This code assumes that you hold all your articles in a struct similar to this:
struct ArticleData
{
ArticleWidget *widget;
QString title;
...
};
and have a vector of them in your outer widget class:
QVector<ArticleData*> articles;
Related
I want to change a QWidget in a QMainWindow dynamically. Therefore, the old widget (if it exists) will be deleted, a new one will be constructed and added to the main window.
The widget (_visualization) is a QMainWindow itself that contains a menu bar and a widget that shows an OSG scene graph.
If I don´t call show() on the new widget, I will only see the menu bar, but not the scene graph.
My goal is to call show(), when the user clicks on a button. The button is connected with the outer QMainWindow (MyQMainWindow).
Unfortunately, when I call show() on _visualization in the connected method, the scene graph will not be shown. In contrast to that, the scene graph will be shown, if I call it in the constructor method (loadVisualization(...)).
MyQMainWindow::MyQMainWindow(QWidget *parent ) :
QMainWindow(parent) {
...
loadVisualization(...);
connect(_ui->nextButton, SIGNAL(clicked()), this, SLOT(showNext()));
...
}
void MyQMainWindow::loadVisualization(QString filePath) {
if (_visualization) {
_heightWidgetLayout->removeWidget(_visualization);
delete _visualization;
}
_visualization= new HeightVisualization(0, filePath);
_visualization->setParent(_mainWindowWidget);
_heightWidgetLayout->addWidget(_visualization);
//_visualization->show(); // will work here
}
void MyQMainWindow::showNext() {
_visualization->show(); // does not work here!
}
I know that QT will call setVisible(...) on the widget. This method first tests some states in QT (testAttribute(Qt::WA_WState_ExplicitShowHide) && !testAttribute(Qt::WA_WState_Hidden)). If I call show() in showNext(), these tests lead to a return without any change.
Is it a problem with connectors and slots? Is there a possibility to show the widget, when the user clicked on a button?
What I have learned is that it is easy to use stackedWidget.
You can then programmatically change it with this
currentPageIndex = (currentPageIndex + 1) % 3;
ui->stackedWidget->setCurrentIndex(0);
The 3 can be the total pages you have in your stack widget. You can either use currentPageIndex, or you can just create some constants with the page ids like I have done with the 0.
I have a Qt Desktop aplication which has several top-level widgets. Subwidgets of top-level widgets can be moved between top-level widgets by using drag-and-drop mechanism.
The problem i have now is to drop a sub-widget outside any of existing top-level widgets and create a new top-level widget to contain this one. Lets call this separation.
Can this be done using drag-and-drop? I could not find a way where my dropEvent goes?
Can i want to handle the drop event in my application even if the drop place is not allowed? Maybe a mouse release or something?
I cannot change everything now but also a question for the future. Is docking/undocking a better way to do this?
Regards
Mihai
I found a way to do this. When drag moves outside of the application widgets QDrag object emits a targetChanged signal with 0 parameter.
So i inherited from QDrag and then emit a custom signal in destructor if the target() is null.
The only problem is that the cursor looks like interdiction of drop and this i could not fix because QDrag can only set cursor pixmap for valid actions like Move or Copy or Link
Update:
Here is the inherited class.
class TabDrag: public QDrag
{
Q_OBJECT
public:
explicit TabDrag(QWidget *dragSource);
~TabDrag();
signals:
void tearOff(); /// emit tearOff signal if the QDrag object is destroyed and target was null
};
TabDrag::TabDrag(QWidget *dragSource):QDrag(dragSource)
{
}
TabDrag::~TabDrag()
{
// check if we need to detach this tab
if(!target())
{
emit tearOff();
}
}
The tearOff signal should be connected to whatever you want to happen. In my case i pull out the widget from the tab and change parent to a new window.
Example of usage
void MyTabBar::mouseMoveEvent(QMouseEvent* event)
{
..................
TabDrag * drag = new TabDrag(this);
drag->setMimeData(mimeData);
drag->setPixmap(*m_tabPixmap.data());
drag->setHotSpot(QPoint(m_dragStartPos.x() - tabAtRect.x(), m_dragStartPos.y() - tabAtRect.y()));
drag->exec();
connect(drag, SIGNAL(tearOff()), this, SLOT(onTearOff()));
}
I am trying to develop an image gallery application using Qt Framework. The application loads all the images from the selected folder and those images are displayed using QListView control.
But now i want to reduce the memory consumption by loading only the images that are visible to user. Since there is no direct function to get all the visible items in the view, i am not able to achieve this.
You can get the visible items of a list view using the indexAt function. For more details and an example you can check the following article:
http://qt-project.org/faq/answer/how_can_i_get_hold_of_all_of_the_visible_items_in_my_qlistview
I found it! You have to connect the vertical scrollbar of the listwidget to a signal:
connect(ui->listWidget->verticalScrollBar(), SIGNAL(valueChanged(int)), this, SLOT(launch_timer()));
Every time the user scrolls, the valuechanged(int) signal is being omitted! The thing is that you shouldn't run the code provided by webclectic in this question every time the value of the vertical scrollbar of the listwidget changes, because the program will be unresponsive with so much code to run in so little time.
So, you have to have a singleshot timer and point it to the function that webclectic posted above. When launch_timer() is called, you do something like this:
if(timer->isActive()){
timer->stop();
timer->start(300);
}
else
timer->start(300);
and the timeout() signal of timer will be connected to the slot webclectic talked about. This way, if the user scrolls quickly all the way down only the last items will be updated. Generally, it will be updated anything visible for more than 300 milliseconds!
I think what you need is to implement your own model (take a look to the QAbstractListModel documentation) so that way you could decide when you have to load more images to show and maybe free some of the images that became non-visible.
although this is not so simple in Qt 4 but
it is always simple to copy below:
#include <private/qlistview_p.h>
class QListViewHelper : public QListView
{
typedef QListView super;
inline QListViewHelper() {} //not intended to be constructed
public:
inline static QVector<QModelIndex> indexFromRect(const QListView *view,
const QRect &rect)
{
const QListViewPrivate *d = static_cast<const QListViewPrivate *>(QObjectPrivate::get(view)); //to access "QListViewPrivate::intersectingSet(...)"
const QListViewHelper *helper = static_cast<const QListViewHelper *>(view); //to access "QListView::horizontalOffset()"
return d->intersectingSet(rect.translated(helper->horizontalOffset(), helper->verticalOffset()), false);
}
inline static QVector<QModelIndex> visibleItems(const QListView *view)
{ return indexFromRect(view, view->rect()); }
inline static QModelIndex firstVisible(const QListView *view)
{ return visibleItems(view).value(0); }
inline static QModelIndex lastVisible(const QListView *view) {
const QVector<QModelIndex> &items = visibleItems(view);
return items.value(items.count() - 1);
}
};
void ourTest(const QListView *view) {
QModelIndex &index = QListViewHelper::firstVisible(view);
qDebug("QListViewHelper: first visible row is %d", index.row());
index = QListViewHelper::lastVisible(view);
qDebug("QListViewHelper: last visible row is %d", index.row());
}
usage:
QModelIndex &index =
QListViewHelper::firstVisible(listViewPointerHere)
note: since it does use Qt 4.8 private-headers it may no longer work in latter versions and will need some changes.
You can keep track of all the elements that are drawn per paint event. I used a delegate and overloaded the paint event.
I also overloaded the paint event in the view. During this call, all the visible delegates will get a paint event.
If you just need to know if an item is visible, you can increment a frame count in view->paintEvent and set that number in the delegate item. The item is visible of the item matches the current frame number.
If you need a list of all visible items, clear the visible item list in view->paintEvent and add each item in the int the delegate->paintEvent to the visible items list.
I'm working in a project where I need to open (show or popup) automatically the items in the QMenuBar.
Let's say I have the next menu bar:
File Edit Help
-op1 -op1 -op1
-op2 -op2 -op2
To set an action (show the menu associated with that action) I use:
menuBar->setActiveAction(mymenuactionpointer);
As I know, I can use one of the following to get a list of pointers to the elements of QMenuBar:
QMenuBar::actions();
or
QList<Object*> lst1 = QMenuBar::findChildren<QObject*>();
QList<Object*> lst2 = QMenuBar::findChildren<QAction*>();
When I use QMenuBar::findChildren<QAction*>() or MenuBar::actions() I got a list of the menus in menubar, I mean, I got "File, Edit, Help" from my QMenuBar, the size of the QList in this case is 3.
When I use QMenuBar::findChildren<QObject*>() I got a list of QObject of size 6, which is the correct number of items in the menu bar. However, I have tried cast to QAction*
QAction *a = (QAction *)lst1.at(0);
QAction *a = qobject_cast<QAction*>(lst1.at(0));
QAction *a = dynamic_cast<QAction*>(lst1.at(0));
In all this cases a is not NULL, but when I try to get the action name QAction::title() it always causes me segmentation fault.
I have been searching and I found here that after getting the menubar actions list, one can ask to QAction::menu() (which returns a valid QMenu pointer if the item is a menu) to know if the item is a QMenu, if yes, one can repeat getting the actions list of that menu, and continue iterating. But this does not work for me, I expected that for
QList<Object*> lst2 = QMenuBar::findChildren<QAction*>();
each element "File, Edit Help" QAction::menu() returns a valid menu pointer, so I could get the list of the actions of each menu, but this does not work at all for me.
The correct way to enumerate a QMenu is to use the actions() functions, but there is a catch - some of the actions are submenus, and they need to be iterated recursively. In fact, each QMenu is associated with a QAction, and they both hold pointers to each other - see QMenu::menuAction() and QAction::menu().
It is crucial to understand that each QMenu is also associated with a QAction. So knowing that, the proper implementation is the following:
void enumerateMenu(QMenu *menu)
{
foreach (QAction *action, menu->actions()) {
if (action->isSeparator()) {
qDebug("this action is a separator");
} else if (action->menu()) {
qDebug("action: %s", qUtf8Printable(action->text()));
qDebug(">>> this action is associated with a submenu, iterating it recursively...");
enumerateMenu(action->menu());
qDebug("<<< finished iterating the submenu");
} else {
qDebug("action: %s", qUtf8Printable(action->text()));
}
}
}
Below is how to iterate through every menu item in the menu bar, it will also seek out any menus underneath so there is not need for recursive calling here.
// assuming you have a private QActionGroup* actions; defined in the header..
// ...and a slot named 'onAction(QAction*)' as well... this should work:
QList<QMenu*> lst;
lst = ui->menuBar->findChildren<QMenu*>();
actions = new QActionGroup(this);
foreach (QMenu* m, lst)
{
foreach (QAction* a, m->actions())
{
actions->addAction(a);
}
}
connect(actions,SIGNAL(triggered(QAction*)),this,SLOT(onAction(QAction*)));
As you can see, you can then connect a master slot to handle the various events an action might bring up (i just showed triggered here but you get the idea). Hope this helps.. someone..
Notes
I used the QActionGroup for example purposes on using the list you might iterate through, but you really shouldnt use that unless you are dealing with radio groups since thats what its for. Secondly, if you want the actions because you plan to link them into a single method to handle all items, i suggest you use QMenu's triggered/hovering signals or if you need to know when a menu is about to pop up, you'll need QMenuBar's aboutToShow() signal. I cant think of a reason (for me anyway) that you cant do what you need in those signals since you are passed the QAction* in the slot. But if you MUST do it the otherway, you can do it the way I showed above, you just might not want to use the QActionGroup because of radio grouping is what it is designed for. (you can work around that by not adding items that are 'checkable' into the group.
The reason the qobject_cast is failing is that there are only three QActions with the QMenuBar as the parent. The other three are different QObjects (my guess is the three QMenus), so the cast fails. The QActions associated with those menus are then under those, not the root QMenuBar. I fail to see why you can't build a master list of QActions by recursively iterating through the QMenus.
You may be able to just use the QAction pointer from your UI definition if you are after a known menu, that might not trigger the parent menus. If you are trying to automate testing, trigger() on your desired QAction is probably as detailed as you need. If you are trying to do things in response to user actions, modifying toolbars is probably a better means of contextual feedback, as it doesn't break focus. Some more details on what you're actually trying to accomplish would help.
this puts it all together:
template <class Function>
class QMenuBarIterator {
QMenuBar *i_barP;
void iterate_sub(Function f, size_t tabsL, QMenu* m) {
foreach (QAction *action, m->actions()) {
f(tabsL, action);
if (action->menu()) {
iterate_sub(f, tabsL + 1, action->menu());
}
}
}
public:
QMenuBarIterator(QMenuBar *barP) : i_barP(barP) {}
virtual void operator()(size_t levelL, QAction *actionP) {
}
void iterate(Function f) {
QList<QMenu *> menuBar = i_barP->findChildren<QMenu *>();
foreach (QMenu* m, menuBar) {
f(0, m->menuAction());
iterate_sub(f, 1, m);
}
}
};
/***************************************************************************/
class CMenuLogger {
public:
void operator()(size_t tabsL, QAction *action) {
SuperString tabStr(GetIndentString(tabsL)); // returns a string with tabsL tab characters in it
if (action->isSeparator()) {
qDebug("%s-------------------", tabStr.utf8Z());
} else {
qDebug("%s%s (%s)",
tabStr.utf8Z(),
qUtf8Printable(action->text()),
qUtf8Printable(action->objectName()));
}
}
};
then in your main:
{
QMenuBarIterator<CMenuLogger> bar(ui->menuBar);
bar.iterate(CMenuLogger());
}
I am implementing QAbstractTableModel and I would like to insert a QPushButton in the last column of each row. When users click on this button, a new window is shown with more information about this row.
Do you have any idea how to insert the button? I know about delegating system but all examples are only about "how to edit color with the combo box"...
You can use
QPushButton* viewButton = new QPushButton("View");
tableView->setIndexWidget(model->index(counter,2), viewButton);
The model-view architecture isn't made to insert widgets into different cells, but you can draw the push button within the cell.
The differences are:
It will only be a drawing of a pushbutton
Without extra work (perhaps quite a bit of extra work) the button won't be highlighted on mouseover
In consequence of #1 above, you can't use signals and slots
That said, here's how to do it:
Subclass QAbstractItemDelegate (or QStyledItemDelegate) and implement the paint() method. To draw the pushbutton control (or any other control for that matter) you'll need to use a style or the QStylePainter::drawControl() method:
class PushButtonDelegate : public QAbstractItemDelegate
{
// TODO: handle public, private, etc.
QAbstractItemView *view;
public PushButtonDelegate(QAbstractItemView* view)
{
this->view = view;
}
void PushButtonDelegate::paint(
QPainter* painter,
const QStyleOptionViewItem & option,
const QModelIndex & index
) const
{
// assuming this delegate is only registered for the correct column/row
QStylePainter stylePainter(view);
// OR: stylePainter(painter->device)
stylePainter->drawControl(QStyle::CE_PushButton, option);
// OR: view->style()->drawControl(QStyle::CE_PushButton, option, painter, view);
// OR: QApplication::style()->drawControl(/* params as above */);
}
}
Since the delegate keeps you within the model-view realm, use the views signals about selection and edits to popup your information window.
You can use setCellWidget(row,column,QWidget*) to set a widget in a specific cell.