Using custom QWidgets in QListWidgets

Hubbard

QListWidgetItem* exampleUnitQLWIAddress = new QListWidgetItem(tr("example"), ui->UnitList);

QListWidgetItem* exampleButtonAddress = new QListWidgetItem(tr("example"), ui->UnitList);

BioBloomUnit* exampleUnitAddress = new BioBloomUnit(this);

QPushButton* exampleButton = new QPushButton;

exampleUnitQLWIAddress->setSizeHint(exampleUnitAddress->ribbonAddress->sizeHint());

ui->UnitList->setMovement(QListView::Free);

ui->UnitList->setItemWidget(exampleUnitQLWIAddress, exampleUnitAddress->ribbonAddress);

ui->UnitList->addItem(exampleUnitQLWIAddress);

ui->UnitList->addItem(exampleButtonAddress);

ui->UnitList->setItemWidget(exampleButtonAddress, exampleButton);

connect(ui->pushButton, SIGNAL(released()), exampleUnitAddress, SLOT(unitButtonPressSlot()) );

I am kind of new to coding in Qt and am looking for a method to list my custom graphical widgets into a list, the class I have created name 'BioBloomUnit' contains a member class UnitRibbon which is a designed graphical QWidget, this is not appearing in the list whereas the QPushButton is.

mrjj

Hi
QListWidgetItem* exampleUnitQLWIAddress = new QListWidgetItem(tr("example"), ui->UnitList);
ui->UnitList->setItemWidget(exampleUnitQLWIAddress, exampleUnitAddress->ribbonAddress);

Are you setting the QListWidgetItem as ItemWidget ??

should that not be the
exampleUnitAddress = new BioBloomUnit(this); ?

Hubbard

I don't understand :/
The declaration for that function is:-
void QListWidget::setItemWidget(QListWidgetItem *item, QWidget *widget)
and its description is sets the widget in the item
which I assume means it puts my custom widget inside the QLWI so that it can be added to the list?

mrjj

@Hubbard
Oh, sorry, misread the names it seems.
But if u insert exampleUnitAddress->ribbonAddress
are you inserting a widget that lives in other widget ?
When you insert a QButton its not inside other widget.
That seems to be the difference ?

Hubbard

The QWidget class 'UnitRibbon' (or UnitRibbon *ribbonAddress) is a member class of BioBloomUnit QObject, with a designed UI

SGaist

Hi,

Why are you trying to show an inner widget rather than the full BioBloomUnit widget ?

Hubbard

@SGaist
The BioBloomUnit isn't a widget with its own graphics (its a QObject), it stores all of the necessary data for an instance of the unit in my project AS WELL AS its own QWidget unitRibbon which displays some of the data, which I want organised into lists

SGaist

Then this looks bad. You should decouple the data from their graphic representation aka MVC.

Since you are already using Qt's related class. You should consider implementing a QAbstractListModel that will wrap your list of BioBloomUnit and use a QListView to show them.

By the way, what is ribbonAddress for a widget ?

Hubbard

ribbonAddress is a pointer to a UnitRibbon class and is a member in BioBloomUnit, its a widget with its own UI file, BioBloomUnit is NOT a widget and is a normal QObject class, I was to display all of the UnitRibbons for each unit in a list.

SGaist

That I understood, hence my suggestion for a separation of concerns. BioBloomUnit should not care about the GUI that should show the data it represents.

Hubbard

Would it be better if the UnitRibbons exist in the mainWindow and instead take BioBloomUnit as an argument (either by constructor or member method) to get their data?

Hubbard

so I updated my code to the following

UnitRibbon* exampleRibbonAddress = new UnitRibbon;
QListWidgetItem* exampleItemAddress = new QListWidgetItem(ui->UnitList);
//exampleItemAddress->setSizeHint(exampleRibbonAddress->sizeHint());
ui->UnitList->setItemWidget(exampleItemAddress, exampleRibbonAddress);
ui->UnitList->addItem(exampleItemAddress);

Now it only shows the top half of the widget, when the sizeHint is uncommented it becomes invisible entirely

mrjj

@Hubbard
Hi
Setting size hint is good idea.
It will use that for widget size when placed on "row"

SGaist

Might be a silly question but are you sure your properly set the layouts on your widgets ? Having to call sizeHint like that is surprising.

Hubbard

I have removed the graphical widget from my class and made it a separate class and now it is displaying, I'm surprised it works like that, however I've run into a different yet related issue:-

exampleUnitAddress = new BioBloomUnit(this);        //instance example

setupOtherWindows();
setupPushButtons();

UnitRibbon* exampleRibbonAddress = new UnitRibbon;
QListWidgetItem* exampleItemAddress = new QListWidgetItem(ui->UnitList);
exampleItemAddress->setSizeHint(exampleRibbonAddress->size());
ui->UnitList->setItemWidget(exampleItemAddress, exampleRibbonAddress);
ui->UnitList->addItem(exampleItemAddress);

//UnitRibbonPressSlot() calls BioBloomUnit::UnitWindow->show()

connect(ui->ExampleButton, SIGNAL(released()), exampleUnitAddress, SLOT(unitRibbonPressSlot()));

connect(ui->UnitList, SIGNAL(itemClicked(exampleItemAddress)), exampleUnitAddress, SLOT(unitRibbonPressSlot()) );

ExampleButton (a QPushButton on the ui) successfully opens the unit's window, however pressing on the Ribbon for the example Unit does not.

mrjj

Hi
When using the old SLOT and SIGNAl macros, you should always
check the return value of connect.
Also you seem to mix signatures/odd syntax
connect(ui->UnitList, SIGNAL(itemClicked(exampleItemAddress)), exampleUnitAddress, SLOT(unitRibbonPressSlot()) );
What is exampleItemAddress ?
and unitRibbonPressSlot should also accept such paramter
Are you sure that UnitLists signal itemClicked have that signature ?

Hubbard

void itemClicked(QListWidgetItem *item)

can you explain your response more please?

It takes in the item instanced above (and shown in the list) and has no return

Hubbard

What do you mean by the 'old' signal and slot macros?

Hubbard

Ah I see, the signals are only allowed to be passed parameter types, not names, so how do I link the specific item clicked on to it's specific unit's window?

mrjj

@Hubbard
Hi
Yes for connect, you only list the type and not the parameter name.

The actual parameter is added by the widget that emit the signal.
( in this case when you click something)

Normally, the SLOT should accept the same paramter(s)

by old i mean
https://wiki.qt.io/New_Signal_Slot_Syntax
Its possible to use other syntax that fails at compile time.
The price is a ugly syntax if there are overloaded signals ( one send index, other send string as example)

Hubbard

@mrjj
Could you explain what you meant about the actual parameter is passed by the item that's emits the signal please

How could I use this to open a different window for a different item?

jsulm

@Hubbard Please read http://doc.qt.io/qt-5/signalsandslots.html
Parameters are not passed at the time you connect a slot to a signal (how would it be possible?), but at the time the signal is emitted. So, the object emitting the signal passes the parameter.
For example lets say you have a class with void someSignal(int someParameter) signal, then an instance of this class would emit the signal like this:

emit someSignal(10);