So in my UI designer I have a ScrollArea Widget, I then in my MainWindow.cpp, I create a QGraphicScene and a QGraphics View. I create a new widget and give that widget a QVBoxLayout so that it will auto-size(which is correct to my understanding).
I then use ui->scrollArea->setWidget(widget); to make this new widget the child of my scrollView.
All of this seems correct because I have scroll bars that I can navigate my scene with. However; using the line ui->scrollArea->horizontalScrollBar()->setValue(0); still has no effect on the scroll bar values.
scene = new QGraphicsScene();
scene->setSceneRect(0,0,2500,2500);
view = new QGraphicsView(scene);
QWidget *widget = new QWidget;
view->setBackgroundBrush(Qt::white);
QVBoxLayout* bLayout = new QVBoxLayout(widget);
ui->scrollArea->setWidget(widget);
bLayout->addWidget(view);
widget->show();
ui->scrollArea->horizontalScrollBar()->setValue(0);
ui->scrollArea->verticalScrollBar()->setValue(0);
I just had the this problem. Then, after debugging with ui->scrollArea->verticalScrollBar()->value() I realized that the scrolling area has no size before the component is show on the screen, i.e., it does not change the scrolling because it is not visible yet.
This is a sample Python code, but the is the same for C++, except the Language Syntax.
from PyQt5.QtWidgets import QDialog
...
dialog = QDialog()
...
verticalScrollBar = dialog.QPlainTextEdit.verticalScrollBar()
horizontalScrollBar = dialog.QPlainTextEdit.horizontalScrollBar()
# Has no effect, if you print the values, you will see always 0
verticalScrollBar.setValue( horizontalScrollBar.maximum() )
horizontalScrollBar.setValue( horizontalScrollBar.minimum() )
dialog.show()
# Now it has effect
verticalScrollBar.setValue( horizontalScrollBar.maximum() )
horizontalScrollBar.setValue( horizontalScrollBar.minimum() )
Autoscroll PyQT QTextWidget
If you are sure to address the correct scrollbar (as pointed in the comments by thuga), maybe check if your scroll area is modified after that init. I mean I'm not sure of the bahaviour, but if you modified some text in your widget for example, I think the scrollbar will be impacted.
You may need to catch some of your widget's event to reapply those:
ui->scrollArea->horizontalScrollBar()->setValue(0);
ui->scrollArea->verticalScrollBar()->setValue(0);
If it doesn't help, you should try to debug by tracking scrollbar value with
ui->scrollArea->verticalScrollBar()->value()
and see if your set is well applied, and maybe when it is overriden
Just in case, you may also try some of the methods indicated here, but it's probably not relevant to your issue: setValue of ScrollBar Don't work at first time
Related
I have two widgets (both QFrames), none of them have any title bar associated with them (which I achieve through setWindowFlags(Qt::FramelessWindowHint)). One of them is a main widget, and the other a sidebar sort of widget, which is supposed to stick to it at its right boundary (its height being approximately 1/4th of the main widget).
I cannot keep them both in a transparent QFrame with static positioning, since the main widget is draggable through its top (since title bar is missing on it, I do it manually by intercepting mousepress/mousemove events and moving it accordingly). The custom drag on the main widget works fine, but when I try to move the sidebar along with, a very obvious visual delay shows up between the two, there are momentary gaps visible between the two while dragging the main widget to the left, or momentary overlapping between the two when dragging the main widget to the right (the sidebar is not draggable, no drag logic is implemented for it).
How do I 'glue' these two widgets together, such that they move together all the time without any delay? I browsed the Qt docs, it may be possible that QDockWidget can help here, but I could not understand how. The main widget here is not a QMainWindow.
Platform - OS X Yosemite, Qt 5.3.1, 32 bit.
You should definitely use QDockWidget here.
Make your "main widget" derive from QMainWindow rather than QFrame (it may not be "obvious" as QMainWindow does not derive from QFrame, but it should not be such a big deal).
Then, encapsulate your second widget within a QDockWidget and dock it in the main widget like that:
// secondWidget being your QFrame based widget
// mainWidget being your "main widget"
QDockWidget* dockingBar = new QDockWidget("My bar", mainWidget );
dockingBar->setWidget( secondWidget );
// dock on left side, change first parameter to dock somewhere else:
mainWidget->addDockWidget( Qt::LeftDockWidgetArea, dockingBar );
An alternative is to create a third widget that would become your top-level widget and use a QLayout to insert your two QFrames in this new one:
QWidget* newTopLevelWidget = new QWidget();
// QHBoxLayout to have mainWidget on the left hand side of secondWidget
// Replace by QVBoxLayout to have mainWidget on top of secondWidget
QLayout* layout = new QHBoxLayout( newTopLevelWidget );
layout->addWidget( mainWidget );
layout->addWidget( secondWidget );
I'm looking for a super simple example, and can't seem to find one. I have a MainWindow. When a button gets pressed I want to create a new window that gets opened up in the layout of MainWindow, to become a part of the mainwindow.
I have the code that sets up when a button is pushed to call this slot...when it gets called my QLabel shows up, but my QWidget does not
QWidget *test = new QWidget();
test->setGeometry(QRect(100,100,100,100));
layout->addWidget(test,0,0)
//Operation Mode
QLabel *operationalModeLabel1 = new QLabel("TEST");
layout->addWidget(operationalModeLabel1,2,1);
The reason for "lack of examples" is that you think of it wrong. What you describe is done all the time, by every single Qt example that uses layouts! I mean it. It doesn't matter when you add a widget to a layout. There's nothing magical about adding widgets "now" vs. adding them "later".
Just think of the title of the question: it makes no sense. All widgets must be added to layouts that already exist! By definition, no less. If there's no layout, how could you add a widget to it?
Your code is wrong, that's all. It's always pointless to set a geometry on a widget that is to be managed by a layout. As soon as you add it to the layout, the layout will change the geometry.
Since you're adding an empty widget into the layout, you most likely won't be able to see it. That's why the label shows up - it's not an empty widget.
If you want a widget that has a fixed size, to make it easier to notice, just set the fixed size on it. Even better, make it red so that it stands out.
QWidget * test = new QWidget();
test->setStyleSheet("QWidget { background-color: red }");
test->setFixedSize(100, 100);
layout->addWidget(test, 0, 0);
I have a nice widget that basically looks like a dialog box with a bunch of QSliders on it. The number of sliders varies depending on the situation when the dialog (not an actual QDialog; just a QWidget) is invoked.
Since the varying number of sliders causes the box to be different sizes at different times, I now want to clean things up a bit by confining the sliders to a QScrollArea. If I understand things correctly, such a scroll area would display however many sliders fit within its height, and one could scroll down to see the rest if there were more.
Anyway, I tried a (somewhat complicated) procedure like this:
In constructor of custom QWidget class (m_variableName = member variable):
CustomScrollBox::CustomScrollBox(QWidget* _parent){
setWindowTitle(...);
...
m_scrollArea = new QScrollArea(this);
m_scrollAreaBox = new QGroupBox(m_scrollArea);
m_layout = new QGridLayout();
m_scrollAreaBox->setLayout(m_layout);
m_scrollArea->setWidget(m_scrollAreaBox);
m_scrollArea->setFixedHeight(250);
m_bottomButton = new QPushButton(this); //probably irrelevant
...
[connect calls, etc.]
}
After the constructor, the real, situation-dependent set-up of sliders occurs:
void
CustomScrollBox::SetUpWidgets(){
for([however many sliders the situation calls for]){
CustomSlider* s = new CustomSlider(this, label); //just a QWidget consisting of a
//QSlider and a QLabel to
//the left of it
..
m_layout->addWidget(s, [grid dimensions as needed]);
}
...
[set text on bottom button, etc., and add it as well]
}
This process causes nothing to show up on the overall dialog, except for an immobile scroll bar on the left. What, if possible, is the proper order of initialization steps to make this work? My guess is that I might have given something the wrong parent or set a layout at the wrong time, but the rearrganements I've tried so far haven't worked...
First of all you do not need to create explicit members for child widgets and layout to your CustomScrollBox unless you need to access them later (even then you might track them down through their child relationship to your CustomScrollBox). In particular, having set the layout of a widget you can use QWidget::layout to get QLayout* and downcast it to QGridLayout* or QVBoxLayout*. Secondly you are supplying parents to most of the child widgets ctors. Normally you should not do that as e.g. the layout to which the widget is added will take the ownership i.e. the layout will become parent to the added widget. Below is in principle what I would do. It will point you in a better direction at least.
CustomScrollBox::CustomScrollBox(QWidget* parent)
: QWidget(parent)
{
setWindowTitle(...);
...
QVBoxLayout* vBoxLayout(new QVBoxLayout);
QScrollArea* scrollArea(new QScrollArea);
vBoxLayout->addWidget(scrollArea);
QGroupBox* groupBox(new QGroupBox);
QGridLayout* gridLayout(new QGridLayout);
gridLayout->addWidget(.../*whatever buttons etc*/)
groupBox->setLayout(gridLayout);
scrollArea->setWidget(groupBox);
setLayout(vBoxLayout);
...
[connect calls, etc.]
}
I have a QMainWindow whose central widget has been set to a QGraphicsView viewing a black scene (for test purposes). Note that in the code below, I use my class derived from QGraphicsView, called CQtGlView, which reimplements only the resizeEvent function.
Regardless of whether I add the view directly,
CQtMainWindow::CQtMainWindow() {
m_glView = new CQtGlView();
setCentralWidget(m_glView);
}
or stick it in a layout with margins of 0 in a dummy widget,
CQtMainWindow::CQtMainWindow() {
m_glView = new CQtGlView();
QWidget* dummy = new QWidget();
QHBoxLayout* l = new QHBoxLayout();
l->setContentsMargins(0,0,0,0);
l->addWidget(m_glView);
dummy->setLayout(l);
setCentralWidget(dummy);
}
I get an unwanted grey border around the widget.
The screenshot below illustrates the problem, visible between my scene and the windows aero border.
This would not be a problem if my application did not allow switching to full screen. The border is very obvious once the rest of the screen is black.
It's possible this area represents the DockWidgetAreas around the outside of the central widget.
Is there anything I can do to solve this other than not use QMainWindow? (Undesirable due to my use of menuBar, tool bars, and statusBar.)
It turns out that QGraphicsView derives from QFrame, where I assumed it was only a QWidget.
The solution to this problem was to call setFrameStyle(QFrame::NoFrame); in the constructor of my QGraphicsView subclass. Or if it was not a subclass,
m_glView->setFrameStyle(QFrame::NoFrame);
Have you tried setFrameShape(QFrame::NoFrame) on the QGraphicsView?
Hello everyone, here is my code:
myplot *p = new myplot(gao.structpayloadgraph,
gao1.structpayloadgraph,
gao.structcol-2, "payload");
ui->scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
ui->scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
ui->scrollArea->setWidgetResizable(false);
p->resize(ui->scrollArea->size().width(), ui->scrollArea->size().height());
ui->scrollArea->setWidget(p);
I want p to take up the full available space of the scrollbar area and fit itself. However, the appearance looks 'squeezed' even though I called the resize function. What should I do to achieve the desired effect?
You have to treat the scroll area content widget as a normal QWidget. If you want automatic resize and you must use layouts in Qt. Try the following :
QVBoxLayout layout = new QVBoxLayout( ui->scrollAreaContent);
layout->setMargin(0);
layout->setContentsMargins(0,0,0,0);
layout->setSpacing(0);
ui->scrollAreaContent->setLayout( layout);
layout->addWidget(p);
NOTE: ui->scrollAreaContent is a guess, but I think you are using ui files and default content widget is named like that ...
Go to the top right of the QT creator designer screen (Object, Class), right click on the QScrollArea row and select the "Lay Out" menu item, choose a layout (eg vertical or horizontal layout), make sure that your QWidget has a minimum or above size policy. Your scroll widget should now resize with the layout.