Here is what I am doing： mainwindow with MdiArea, and I add a scrollarea widget (which contains a image label) to MdiArea as a subwindow. It doesn't work (the picture doesn't show).
Here is my code:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QScrollArea sa;
QPixmap *image = new QPixmap("2.jpg");
QLabel* imageLabel = new QLabel();
imageLabel->setPixmap(*image);
sa.setWidget(imageLabel);
sa.show();
ui->mdiArea->addSubWindow(&sa);
}
But when I use a QLabel as subwindow directly, i.e. replace the last line with:
ui->mdiArea->addSubWindow(imageLabel);
it works perfectly.
Anyone know why this is happening?
QScrollArea sa;
This declares a QScrollArea on the stack. It gets destroyed immediately after the constructor finishes. Allocate it with new like you do for the other widgets and it should start working.
QScollArea *sa = new QScrollArea;
...
ui->mdiArea->addSubWindow(sa);
(And change the sa. to sa->.)
Related
I just begin to work on making a layout with Grid. I tried to make it using the HBoxlayout and VBoxlayout. But How to set the position of the layout. I searched out and I found the setAlignment option but it isn't working on it.
So how to do its postioning of layouts like the image?
this is the layout I want to make
check this out
#include "mainscreen.h"
#include "ui_mainscreen.h"
#include<QLayout>
#include<QPushButton>
MainScreen::MainScreen(QWidget *parent) :
QWidget(parent),
ui(new Ui::MainScreen)
{
ui->setupUi(this);
QGridLayout *layout=new QGridLayout;
QHBoxLayout *hlayout=new QHBoxLayout;
QPushButton *x=new QPushButton;
hlayout->setAlignment(Qt::AlignTop);
hlayout->addWidget(x);
layout->addChildLayout(hlayout);
this->setLayout(layout);
this->show();
}
MainScreen::~MainScreen()
{
delete ui;
}
You can find good information about Layout in this Tutorial from Qt: http://doc.qt.io/qt-5/qtwidgets-layouts-basiclayouts-example.html
Two things that are important for your Layout:
You need to nest several layout. Themain layout will be a VBoxlayout that contains the top and bottom Widget and one HBoxLayout in the middle. The HBoxLayout contain the other two widgets.
Two get different size for the two middle widgtes you need to give either a Stretch factor to the Layout or define sizes for the widgets.
You may consider doing the following
QHBoxLayout *TopLayout = new QHBoxLayout;
QHBoxLayout *BottomLayout = new QHBoxLayout;
QHBoxLayout *MiddleLayout = new QHBoxLayout;
QVBoxLayout *mainLayout = new QVBoxLayout;
QPushButton *topBtn = new QPushButton;
QPushButton *bottomBtn = new QPushButton;
QPushButton *LeftMiddleBtn = new QPushButton;
QPushButton *RightMiddleBtn = new QPushButton;
TopLayout->addWidget(topBtn);
BottomLayout->addWidget(bottomBtn);
// order matters here (i.e. the first addWidget will be placed in the left)
MiddleLayout->addWidget(LeftMiddleBtn);
MiddleLayout->addWidget(RightMiddleBtn);
// order matters here
mainLayout->addLayout(TopLayout);
mainLayout->addLayout(MiddleLayout);
mainLayout->addLayout(BottomLayout);
setLayout(mainLayout);
More convenient and right approach is to use Qt Designer or Qt Creator for this matter.
QMainWindow is a spatial case. It already has a layout set and it is impossible to change layout in widget! Reason is that QMainWindow has lots of other functionalities like menu, docking, status bar.
So how to make it work?
You have to set central widget:
MainScreen::MainScreen(QWidget *parent) :
QWidget(parent),
ui(new Ui::MainScreen)
{
ui->setupUi(this);
auto widget = new QWidget();
setCentalWidget(widget);
auto vLayout = new QVBoxLayout(widget);
// add your stuff here
// some example for testing:
vLayout->addWidget(new QButton("Test button"));
vLayout->addWidget(new QLabel("Nice label"));
vLayout->addWidget(new QTextEdit);
}
Also you are doing something wrong since this line ui->setupUi(this); indicates that you are using Qt Designer (design ui by mouse) and this means that layout should not be setup directly by code!
I have tried this code but the button isn't displaying on the main window.
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QGridLayout>
#include<QLabel>
#include<QPushButton>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QPushButton *l=new QPushButton();
l->setText("abc");
QGridLayout *q=new QGridLayout();
q->addWidget(l);
this->setLayout(q);
this->show();
}
MainWindow::~MainWindow()
{
delete ui;
}
I have tried to change the code even by passing enums for alignment but nothing worked.
When you create new Qt widgets Application, the default form (MainWindow ui) is created with centralWidget to put all other widgets. In your code you created the QGridLayout without a parent, typically such layout should be placed in ui->centralWidget (as far as you are not creating another widget to be set as centralWidget), moreover I assume your mainWindow is shown from main.cpp (need not use show()). your code could thus be:
QPushButton *l=new QPushButton();
l->setText("abc");
QGridLayout *q=new QGridLayout(ui->centralWidget);
q-> addWidget(l);
Try adding the widget to the GridLayout with index using addWidget function
void QGridLayout::addWidget(QWidget *widget, int row, int column, Qt::Alignment alignment = ...)
like:
q-> addWidget(l, 0, 0);
P.S. also consider using better names for your variables!
I have 5 QProgressBars in a QListWidget (ui->listWidget). How can I access the third QProgressBar element and change its value ex. ( progressBar->setValue(40) )
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
a = new QPushButton(this);
connect(a, SIGNAL (clicked()),this, SLOT (clickedSlot()));
}
void MainWindow::clickedSlot()
{
QProgressBar *prog = new QProgressBar(this);
QListWidgetItem *it;
it = new QListWidgetItem(ui->listWidget);
ui->listWidget->insertItem(ui->listWidget->size().height(),it);
it->setSizeHint(QSize(200,50));
ui->listWidget->setItemWidget(it, prog);
}
The following code will obtain the third element in the list and set the progress to 40%.
QProgressBar *bar = qobject_cast<QProgressBar*>(ui->listWidget->itemWidget(pList->item(2)));
if (bar)
bar->setValue(40);
qobject_cast will safely cast the QWidget to QProgressBar, only if the widget is indeed a QProgressBar. If you are sure the third element is a QProgressBar, you can omit the if test if(bar).
See the qt documentation QListWidget and qobject_cast for more information.
Create the definition for the QProgressBar(s) in the class header file, then you can connect things to the setValue slot, or access them directly.
It seems odd to be adding ProgressBars to QListWidgetItems... wouldn't QHBoxLayout be more suitable?
I am attempting to create a specialised QDockWidget, with some contents, that I can use in other Qt5 UIs. To do this, I have created a QDockWidget subclass complete with a UI form, called SpecialDockWidget. The contents (a QTreeWidget) are added in the UI form.
In my main UI, I have added SpecialDockWidget as a QDockWidget promotion, have promoted the desired dock widget, and everything compiles OK. However, when I run the application my promoted dock widget contains the title of the SpecialDockWidget in its title bar, but the contents remain empty. This only happens if the dock widget is made part of the main UI (whether floating or attached), and the dock widget displays the contents successfully if it is instantiated on its own as a top-level widget.
The Qt documentation says the following with regards to QDockWidget::setWidget():
If the dock widget is visible when widget is added, you must show() it explicitly.
Note that you must add the layout of the widget before you call this function; if not, the widget will not be visible.
I have tried calling show() on both the SpecialDockWidget and the contents, and have set the layout myself, but the contents still don't show up.
Can anyone tell me what I might be doing wrong?
EDIT: Some photos showing what's going on:
Dock widget code:
#include "specialdockwidget.h"
#include "ui_specialdockwidget.h"
#include <QVBoxLayout>
SpecialDockWidget::SpecialDockWidget(QWidget *parent) :
QDockWidget(parent),
ui(new Ui::SpecialDockWidget)
{
ui->setupUi(this);
}
SpecialDockWidget::~SpecialDockWidget()
{
delete ui;
}
Main window code:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
// This produces the top-level dock widget
// SpecialDockWidget* w = new SpecialDockWidget();
// w->show();
}
MainWindow::~MainWindow()
{
delete ui;
}
The QDockWidget is created in the Designer so it's not very clear how the tree is added to the QDockWidget. If the tree is simply a child of the QDockWidget it's not correct. You must add the tree to the QDockWidget using QDockWidget::setWidget().
I suggest to not use the Designer to create a subclass of QDockWidget because it seems not possible to add the content correctly. You can do something like this instead.
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent), ui(new Ui::MainWindow)
{
ui->setupUi(this);
QDockWidget *dw = new QDockWidget(this);
QTreeWidget* tw = new QTreeWidget(dw);
dw->setWidget(tw);
addDockWidget(Qt::LeftDockWidgetArea, dw);
dw->show();
}
Of course, if you need to put inside a dock widget a more complex widget, you can create the content with the Designer as a simple QWidget subclass and add it to the dock widget in the same way.
I think your main window's constructor should look like, for example:
MainWindow::MainWindow(QWidget *parent)
:
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
SpecialDockWidget *w = new SpecialDockWidget();
// Add dock widget to the specified area of main window.
addDockWidget(Qt::LeftDockWidgetArea, w);
}
Here is my problem: I created a QDockWidget and put a QGraphicsView in it, while it is floating everything shows up correctly, but if Dock it somewhere, the starting X and Y of my content is on the titlebar of the QDockWidget. Obviously, it should be under:
tilesetWindow = new QDockWidget(tr("Tileset"), this);
tilesetWindow->setMinimumSize(256,256);
tilesetWindow->setFloating(true);
connect(tilesetWindow, SIGNAL(visibilityChanged(bool)), this, SLOT(triggeredTileset()));
tilesetViewer = new QGraphicsView(tilesetWindow);
tilesetViewer->resize(256,256);
tilesetViewer->show();
An image to illustrate this: http://img86.xooimage.com/files/d/7/6/problem-391a96a.png
I've tried to put the QGraphicsView in a container and then in the QDockWidget but had the same result as above. it's the only place where I write code for the QDockWidget.
How can I make it start at the right place when it is Docked?
Edit:
I tried in a new QtProject and made a QDockWidget with a QTextBrowser in it and had the same bug:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QDockWidget *dock = new QDockWidget(this, 0);
dock->setFloating(true);
QTextBrowser *t = new QTextBrowser(dock);
t->show();
}
I'm missing something I think...
Qt Creator 2.4.1
Based on Qt 4.7.4 (32 bit)
After setting the QDockWidget as the Parent, you also need to set the QDockWidget's Widget as the QGraphicsView, or any other you want.
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QDockWidget *dock = new QDockWidget(this, 0);
dock->setFloating(true);
QTextBrowser *t = new QTextBrowser(dock);
dock->setWidget(t);
}