My Qt windows application is ready, but when the application opens, I want the login dialog to be opened, how can I do this? I'm new to Qt and C++. It would be great if it was descriptive.
You have many ways to achieve that... QDialog is a nice way. Here is a short sample using QInputDialog.
One solution could be to add this code in your main.cpp file, and to load the mainwindow only if the credentials are ok.
#include "gmainwindow.h"
#include <QApplication>
#include <QInputDialog>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
GMainWindow w;
QString login = QInputDialog::getText(NULL, "Login","Name ?",QLineEdit::Normal);
if (login == "USER")
{
w.show();
}
else
{
//display an error message
return a.quit();
}
return a.exec();
}
Of course you may want to put an encrypted password and other things, but the idea will be more or less the same.
Related
I cannot force QKeySequence::toString() to return translated shortcut representation despite the fact that it documentation suggests it should work. The docs say: "The strings, "Ctrl", "Shift", etc. are translated using QObject::tr() in the "QShortcut" context." but I am not completely sure what it means by shortcut context. I am probably doing something wrong...
Here is my example. To make it work, I need to copy qtbase_es.qm from Qt installation directory to my project build directory. When the translation is correctly loaded, the action in the menu correctly shows "Action Control+Intro" which is Spanish translation of the shortcut for "Action Ctrl+Enter". But the tooltip on the main window is still "Action (Ctrl+Enter)". I would expect it to be "Action (Control+Intro)", like in the menu. What am I doing wrong?
#include <QAction>
#include <QApplication>
#include <QDebug>
#include <QMainWindow>
#include <QMenuBar>
#include <QTranslator>
int main(int argc, char *argv[])
{
QTranslator spanish;
qDebug() << spanish.load("qtbase_es.qm"); // should return true if correctly loaded
QApplication a(argc, argv);
QApplication::installTranslator(&spanish);
QMainWindow w;
auto menu = new QMenu("Menu");
auto action = menu->addAction("Action");
action->setShortcutContext(Qt::ApplicationShortcut);
action->setShortcut(Qt::CTRL | Qt::Key_Enter);
w.menuBar()->addMenu(menu);
w.show();
QApplication::processEvents(); // I also tried this line but it is useless...
w.setToolTip(QString("%1 (%2)").arg(action->text(), action->shortcut().toString()));
qDebug() << action->shortcut().toString(); // WRONG: returns Ctrl+Enter but I expect Control+Intro
return a.exec();
}
The QShortcut::toString has a SequenceFormat parameter, defaulted to ProtableText. The documentation of the format states, that portable format is intended for e.g. writing to a file.
The native format is intended for displaying to the user, and only this format performs translations.
Try:
qDebug() << action->shortcut().toString(QKeySequence::NativeText);
I'm new to qt mobile development and I have a rather dumb question.
How would I check whether a user runs the app for the first time (both Android and iOS)?
EDIT:
The reason I need this check is that I have an intro SwipeView for the first-timers and after it's read once it should always open the main app screen.
I've tried the way #TrebledJ suggested and it seems to work alright, Or is this stupid to do that in main.cpp?
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QSettings>
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QSettings settings;
QVariant firstRun = settings.value("first-run");
QQmlApplicationEngine engine;
QUrl startingScreen(QStringLiteral("qrc:/main.qml"));
if(!firstRun.isValid())
settings.setValue("first-run", true);
else
startingScreen.setUrl(QStringLiteral("qrc:/start.qml"));
engine.load(startingScreen);
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
Use QSettings to check for a set value.
QSettings settings;
QVariant val = settings.value("first-time");
if (!val.isValid()) {
// ... first run
settings.setValue("first-time", false); // set a value so that the value is valid on the next run
} else {
// ... not first run
}
In QML, there is the Settings QML Type.
import Qt.labs.settings 1.0
Settings {
id: settings
property bool isFirstTime: true
}
Component.onCompleted: {
if (settings.isFirstTime) {
// ... first run
settings.isFirstTime = false;
} else {
// ... not first run
}
}
However, according to documentation:
Note: This type is made available by importing the Qt.labs.settings module. Types in the Qt.labs module are not guaranteed to remain compatible in future versions.
In consideration of the non-guarantee, Felgo/V-Play's API has a Storage QML Type which can also perform the check in QML. (The first example in their documentation implements this.)
i have a few questions regarding the gui of cplusplus using Qt creator
well i output an array using a forloop when user's choice is for example "1"
so in qt i created a button for that and i linked it with another window
so when i press on the button it opens another window
now i want to add the output of the forloop into this window
should i include iostream in the new window's .cpp file?
or what should i enter exactly?
in the mainwindow.cpp file here is the code i used to open a new window
void MainWindow::on_pushButton_clicked()
{
movies movies;
movies.setModal(true);
movies.exec();
}
thanks.
You should add a QTextEdit to your window (can be done via Qdesigner). And give this object a name e.g. Textout. Then in the code you should get a pointer to this object through your ui object. And you can use one of many methods to set the text of this object. setText is one option
ui->Textout->setText(Your_output_as_qstring)
Your can use QTextStream to format your text if necessary. Formating can be done with QString as well.
example:
#include <sstream>
#include <QLabel>
#include <QApplication>
int main(int argc, char *argv[])
{
std::stringstream ss;
for (auto s: {"first line", "second line"})
ss << s << std::endl;
QApplication a(argc, argv);
QLabel l;
l.setText(ss.str().c_str());
l.show();
return a.exec();
}
I'm doing some preparation for an exam using Qt framework and I would like to know how to use QInputDialog and QMessageBox in a basic way (my exams are hand written coding)
The Qt API is really confusing to understand when it comes to using and it was fine for my projects because I could accomplish what I wanted in a really "hacky" way a my set book on the subject is very poorly laid out...
Let me get to the point, what would be a clean way of using QInputDialog and QMessageBox in this scenario:
#include <QApplication>
#include <QInputDialog>
#include <QDate>
#include <QMessageBox>
int computeAge(QDate id) {
int years = QDate::currentDate().year() - id.year();
int days = QDate::currentDate().daysTo(QDate
(QDate::currentDate().year(), id.month(), id.day()));
if(days > 0)
years--;
return years
}
int main(int argc, char *argv[]) {
QApplication a(argc, argv);
/* I want my QInputDialog and MessageBox in here somewhere */
return a.exec();
}
For my QInputDialog I want the user to give their birth date (don't worry about input validation)
I want to use the QMessageBox to show the user's age
I just don't understand what parameters need to go into the QInputDialog and QMessageBox in a basic case like because there don't seem to be any examples out there.
How would I accomplish this?
You can do something like:
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
bool ok;
// Ask for birth date as a string.
QString text = QInputDialog::getText(0, "Input dialog",
"Date of Birth:", QLineEdit::Normal,
"", &ok);
if (ok && !text.isEmpty()) {
QDate date = QDate::fromString(text);
int age = computeAge(date);
// Show the age.
QMessageBox::information (0, "The Age",
QString("The age is %1").arg(QString::number(age)));
}
[..]
I have the following Qt code:
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
ChoosingDialog cdlg;
if(!startWin.exec())
{
// nothing chosen
return 0;
}
if(cdlg.firstWindowSelected)
{
CFirstWindow win;
win.show();
return app.exec();
}
else
{
CSecondWindow win;
win.show();
return app.exec();
}
}
this seems to work but it's giving me an error on "event dispatcher cleanup" in some asm line. I tried to trick a bit and I saw that the problem is related to the app.exec() calling.
Update:
if I add these lines to the ChoosingDialog (this is a simple blank class auto-generated by Qt Creator)
void ChoosingDialog ::closeEvent(QCloseEvent *)
{
exit(1);
}
I receive no errors
Turns out I was using the "singleapplication" class before the QApplication.. and something went wrong on the shared memory lock.
As soon as I restarted my system the exception disappeared... bof.. do you believe in magic?