MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{
this->setupUi(this);
this->setupActions();
this->setWindowTitle(tr("CuteEdit"));
label = new QLabel(tr("No Open Files"));
this->setCentralWidget(label);
label->setAlignment(Qt::AlignCenter);
}
By above code, I get a GUI like this(Its a screenshot of whole screen, Only observe the window displayed in middle of page of ebook). (I used QT Designer)
Now, i want user to select File->Open.. A Dialog appears and file gets selected.. Its contents are to be displayed in *textEdit widget..
Function for that is below..
void MainWindow::loadFile()
{
QString filename = QFileDialog::getOpenFileName(this);
QFile file(filename);
if (file.open(QIODevice::ReadOnly|QIODevice::Text))
{
label->hide();
textEdit->setPlainText(file.readAll());
mFilePath = filename;
QMainWindow::statusBar()->showMessage(tr("File successfully loaded."), 3000);
}
}
The window crashes at line:-
textEdit->setPlainText(file.readAll());
But if i comment the line:-
this->setCentralWidget(label);
i mean i remove label as being the central widget, the program runs as expected.. Why?
And also, I am not clear about the concept of CentralWidget. Pls guide.
JimDaniel is right in his last edit. Take a look at the source code of setCentralWidget():
void QMainWindow::setCentralWidget(QWidget *widget)
{
Q_D(QMainWindow);
if (d->layout->centralWidget() && d->layout->centralWidget() != widget) {
d->layout->centralWidget()->hide();
d->layout->centralWidget()->deleteLater();
}
d->layout->setCentralWidget(widget);
}
Do you see that if your MainWindow already had centralWidget() Qt schedules this object for deletion by deleteLater()?
And centralWidget() is the root widget for all layouts and other widgets in QMainWindow. Not the widget which is centered on window. So each QMainWindow produced by master in Qt Creator already has this root widget. (Take a look at your ui_mainwindow.h as JimDaniel proposed and you will see).
And you schedule this root widget for deletion in your window constructor! Nonsense! =)
I think for you it's a good idea to start new year by reading some book on Qt. =)
Happy New Year!
Are you sure it's not label->hide() that's crashing the app? Perhaps Qt doesn't like you hiding the central widget. I use Qt but I don't mess with QMainWindow that often.
EDIT: I compiled your code. I can help you a bit. Not sure what the ultimate reason is as I don't use the form generator, but you probably shouldn't be resetting the central widget to your label, as it's also set by the designer, if you open the ui_mainwindow.h file and look in setupGui() you can see that it has a widget called centralWidget that's already set. Since you have used the designer for your GUI, I would use it all the way and put the label widget in there as well. That will likely fix your problems. Maybe someone else can be of more help...
I'm not sure I understood your problem, neither what the guys above said (which I guess are valid information) and it seems to be an old topic.
However, I think I had a problem that looks like this and solved it, so I want to contribute my solution in case it helps anyone.
I was trying to "reset" central widget using QLabels. I had three different ones, switch from first to second, then to third and failed to switch back to the first one.
This is my solution that worked:
Header file
QLabel *imageLabel;
Constructor
imageLabel = new QLabel("<img src='/folder/etc.jpg' />");
this->setCentralWidget(imageLabel);
Reset
imageLabel = NULL;
imageLabel = new QLabel("<img src='/folder/etc.jpg' />");
this->setCentralWidget(imageLabel);
Hope that helps
Aris
Related
I'm looking to generate a set of labels and buttons based on some kind of template, but I don't know how to do the template part.
I'll be using a tab widget which I already have set up, and in one the tabs, I want to have a two labels, a custom button, and a textbox. It'll be repeated around 40-50 times (dependent on a given value at startup) and have spacing as needed.
Once I have a template, I foresee calling it in a loop and setting the appropriate displayed text(Label_1, Label_2, etc) and connect statements where needed.
As I said, I don't know how to template parts of the UI so they can be placed in a kind of auto-generation.
I had thought of making one group, copying the xml, and somehow adding it but that doesn't seem to be a proper way. A little new to Qt.
This is roughly the layout I want to repeat. It has two labels, a lineedit, and one pushbutton.
There's no "good" way to do this in QtDesigner/QtCreator. At best you could copy/paste the set of controls 50 times and then in C++ code hide the ones you don't need. But I wouldn't recommend this.
Instead, just create the controls (labels/button/text box), and a layout to hold them, in C++ code, inside a loop which iterates however many times you need at runtime. Insert the controls layout into the tab widget page layout which you have set up in designer mode. It is not difficult, and will actually be more efficient than what QtDesigner produces since that tends to generate more code than you typically need in the first place.
As a starting point, you could look at the C++ code which is generated by the Qt UI Compiler (UIC) tool for your current design (it takes the XML from designer and turns it into C++ code). You can find this in the build folder for your project, typically named something like ui_ClassName.h, probably in a ui subfolder of the build tree.
UPDATE:
Another, possibly better, way to do this is to create the "template" QWidget class/form, which is going to be used multiple times, as a separate object. The "template" design could be created/maintained using QtCreator/Designer (or just directly in C++). The (possible) advantage here is that as the app requirements evolve, the template widget can be expanded with additional functionality or even re-used in other parts of the UI.
For example, I'd assume the text editor and button in the given mockup image will actually need to do something (eg. edit data and submit it). So some basic functionality can be built into the "template" widget, for example to emit a signal with the text contents of the line editor when the button is pressed.
I put together a quick example. I'm creating the simple MainWindow in pure C++ to simplify/shorten the example code. The "template" I'm calling an Editor. The Editor class and UI form I initially created with the QtCreator wizard (New -> Qt Designer Form Class). I then added the label/control widgets in designer mode. And in C++, a textEdited(const QString &text) signal in the header, and in the Editor() constructor a lambda connection to emit that signal when the button is pressed.
The Editor class code is straight out of the QtCreator wizard except for two edits I'm highlighting below. The designer form has two relevant controls: a QLineEdit (lineEdit) and a QPushButton (pushButton). I'll link to the full files below.
Editor.h
// in the Editor class declarations:
signals:
void textEdited(const QString &text) const;
Editor.cpp
// in the constructor, after ui->setupUi(this);
connect(ui->pushButton, &QPushButton::clicked, this, [this]() {
emit textEdited(ui->lineEdit->text());
});
Test harness, including MainWindow subclass and main()
#include <QApplication>
#include <QMainWindow>
#include <QTabWidget>
#include <QBoxLayout>
#include <QMessageBox>
#include "Editor.h"
class MainWindow : public QMainWindow {
Q_OBJECT
public:
MainWindow() : QMainWindow()
{
// set up a tab widget as the window central widget
QTabWidget *tabWidget = new QTabWidget(this);
setCentralWidget(tabWidget);
// the first/only page will contain all the editors in a vertical layout
QWidget *editorsPage = new QWidget(this);
editorsPage->setLayout(new QVBoxLayout());
// add the editors container page to tab widget
tabWidget->addTab(editorsPage, tr("Editors page"));
// Now create a number of editor widgets using our Editor class "template"
int layoutItems = 5; // number of editors needed, could be dynamic
for (int i=0; i < layoutItems; ++i) {
// Create an Editor instance with the tab page as parent
Editor *editor = new Editor(editorsPage);
// Add the editor widget to the tab page layout
editorsPage->layout()->addWidget(editor);
// A simple connection with the editor signal, as way of example.
connect(editor, &Editor::textEdited, this, [this](const QString &text) {
// just show a message box with the editor text
QMessageBox::information(this, tr("Text Edited"), text, QMessageBox::Ok);
});
}
}
};
int main(int argc, char **argv)
{
QApplication app(argc, argv);
MainWindow mainWindow;
mainWindow.show();
return app.exec();
}
#include "main.moc"
Links The full Editor code:
Editor.h
Editor.cpp
Editor.ui
The XML in Qt Creator is for UIC in QMake to generator code for you.
For example, QMake translates your mainwindow.ui to ui_mainwindow.h, and within you will find void setupUi(QMainWindow *MainWindow) with the actual code that creates and places the widgets.
Look at this code, the docs, and create and place the widgets yourself by code.
For example, adding 5 checkboxes to a groupbox by code:
QVBoxLayout *l = new QVBoxLayout(this);
ui->groupBox_4->setLayout(l);
for(int i=0; i<5; i++){
QCheckBox *c = new QCheckBox(this);
l->addWidget(c);
}
I just learned how to set a language pack for my app in Qt, and I am currently have two questions. I wrote a minimal app to show where confused me.
I created a main window, which only contains a QLabel to show text and a QPushButton to change label text from Chinese to English.
And here is my code:
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
chineseTr = new QTranslator;
chineseTr->load("../untitled/Language-Pack_zh-CN.qm");
englishTr = new QTranslator;
englishTr->load("../untitled/Language-Pack_en-US.qm");
QCoreApplication::installTranslator(chineseTr);
mWidget = new QWidget;
setCentralWidget(mWidget);
hLayout = new QHBoxLayout;
mWidget->setLayout(hLayout);
mLbl = new QLabel;
mLbl->setText(tr("Text"));
translateBtn = new QPushButton;
connect(translateBtn, &QPushButton::clicked, this, &MainWindow::translateText);
hLayout->addWidget(mLbl);
hLayout->addWidget(translateBtn);
}
void MainWindow::translateText()
{
QCoreApplication::removeTranslator(chineseTr);
QCoreApplication::installTranslator(englishTr);
}
Question One:
As you can see in the constructor, I loaded the language pack first, or the QLabel will just not show Chinese text. I can either load the Chinese language pack before creating everything else in the constructor, or load in main.cpp before creating MainWindow object. Am I getting this wrong or those language packs just have to be loaded before creating class objects?
Question Two:
As you can see in the code, I clicked the button and to remove the Chinese language pack and install the new translator to load the English language pack. But nothing works. So how can I change language dynamically in the app? I know this question may be simple, but I do not find any useful example online to show me how to do this? So can someone show me a way to do this or give me a hint?
Hope I explain myself clearly, and thanks in advance.
It's important to understand where translation happens: inside tr(...) call. tr(...) returns the translated text. Which means, that replacing translator will influence subsequent calls to tr(...), but have no chance to change texts already displayed in widgets.
Easiest way to do "switch language on the fly" is to introduce method containing all tr(...) calls and call it after replacing translator and in constructor. I believe that code generated from .ui (the ones created by QtDesigner) files already has such method.
void MainWindow::translate()
{
mLbl->setText(tr("Text"));
}
void MainWindow::translateText()
{
QCoreApplication::removeTranslator(chineseTr);
QCoreApplication::installTranslator(englishTr);
translate();
}
in my program the senario is like this, user opens a xml file, the program reads it. Show the units and tests and when the user clicks on the desired test, the program needs to show its step. Since the number of steps always change i need to add the widget by code and delete them. But when i try to add a widget by code and set its position it doesn't show up on the main window. ( i am doing this with a seperate class just make things look neater)
Here is my sample code;
void CStepPanel::addstep()
{
QLabel *label1 = new QLabel("step1");
label1->move(450,50);
}
Do you know doesnt it work ? And how can i do that. Since i am new to qt and programming i am having a hard time about this.
Your widget should have a parent to be shown in an other widget or dialog. You should set a parent for the label. If you want it to be displayed on the main window then a pointer to your QMainWindow should be kept in the class CStepPanel (It could be assigned in the constructor of CStepPanel) :
QMainWindow * mainWindow;
And the addstep is like :
QLabel *label1 = new QLabel("step1");
label1->setParent(mainWindow);
label1->move(450,50);
Is there something special about putting osgEarth's ViewerViewer into a QMdiArea? I created a QMdiArea as central Widget (called setCentralWidget) instead of taking osgEarth's viewer directly as central widget.
QMdiArea *mdiArea = new QMdiArea(this);
setCentralWidget(mdiArea); // call to QMainWindows method, snippet is taken from app's MainWindow
mdiArea->addSubWindow(viewerWidget); // this doesn't work, globe is not drawn
Everything I tried didn't worked... except osgEarth's ViewerWidget is set as central widget of my MainWindow. Also tried MultiViewerWidget without any success but because I need only one view the ViewerWidget should be ok, or not?
I had a look into the examples but didn't succed to use one of them as starting point.
Any hints? Thank's in advance.
you can try this, where Form1 is a QDialog
in main.cpp
int main()
{
QApplication a(argc, argv);
Form1 w=new Form1();//qdialog
.................//do something to initial the map
w.loadWidget(viewerWidget);
w.show();//the order of the loadwiget() and show() is important!!!!!
a.exec();
}
in Form1.cpp
void Form1::loadWidget(QWidget *qwidget)
{
qwidget->setMinimumSize( ui.mdiArea->width(),ui.mdiArea->height());
QMdiSubWindow * subW=ui.mdiArea->addSubWindow(qwidget);
subW->setWindowFlags(Qt::SubWindow | Qt::FramelessWindowHint);
subW->maximumSize();
}
This works well with qt 4.8.4+osgearth 2.3
Try setting the subwindow's geometry before starting the UI.
QMdiSubWindow* sw = mdiArea->addSubWindow(viewerWidget);
sw->setGeometry(...);
Otherwise OSG will probably become confused.
Got this answer by Gwaldron in the osgEarth forum here and it worked.
Also setting a minimum size for the viewerWidget will help (e.g. for positioning on TabWidget). See my question and answer here.
How can i access ui files of children of a class. Lets say MainWindow class has twoa child dialog. I want to access LINEEDIT of dialog so that i can take text from there. Similarly how can i access ui files of parent inside child class in QT. Note: I havn't inherited any thing from Parent class.
I have writen the following code, in order to display a dialog but it won't show!
void MainWindow::displaydialog()
{
ItemDialog dialog= new ItemDialog(this);
dialog->show(); // it is not displaying the dialog
}
and how can i access the ui widgets like check whether ListWidget item has been selected or not.
Here is the code of itemdialog,
#include "itemdialog.h"
#include "ui_itemdialog.h"
#include "mainwindow.h"
ItemDialog::ItemDialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::ItemDialog)
{
ui->setupUi(this);
setWindowTitle("Status Dialog");
setFixedSize(QWidget::sizeHint());
}
ItemDialog::~ItemDialog()
{
delete ui;
}
void ItemDialog::on_pushButton_clicked()
{
MainWindow obj;
obj.okbuttonclicked(ui->lineEdit->text());
}
Please review an example such as this: http://qt-project.org/doc/qt-4.8/designer-using-a-ui-file.html
It explains how to use the ui files that you generate from Qt Designer. You shouldn't really think of them as "ui files" in the sense of accessing them on the widgets in your class. The idea is that you include them, and then use their setupUi() function to apply them to your given class. At that point, everything you created in qt designer, and that is in that ui file, is now a member of your class. They can be accessed via the naming you used in qt designer.
As for why your dialog isn't showing...I don't know because you only included 3 lines of code as an example. Theoretically it should show if Mydialog was properly set up. You could just try changing it to a QDialog to make sure you didn't do anything wrong with your custom class.
It depends what you want that dialog for. Either it's a modal dialog - some kind of a information display or retrival that blocks the function of your program until user reacts, or it's somekind of toolbox or similar, in which case you probably should not use QDialog.
If a modal dialog with a line edits and/or additional features is what you want, you should read up on QDialog in the doc. See the exec() function. Basic usage would go like this:
void MainWindow::displaydialog()
{
ItemDialog *dialog = new ItemDialog();
if (dialog->exec() == someApropriateReturnStatus)
{
QString somevalue = dialog->someValue();
int dialog->someOtherValue();
//do something with the value
}
delete dialog;
}
The point is that the ItemDialog class handles the UI internally and implements the getter functions accordingly, you should not (in most typical cases) access it's UI from outside.
If a simple line edit is all you want, you'd be better off using one of the standard dialogs already implemented in Qt, have a look at the Standard Dialogs Example