Hi I have a problem with Phonon and a slot, it's me first try with this and I hope you could help me,
#include <QMainWindow>
#include <QWidget>
#include <phonon/VideoPlayer>
#include <phonon/VideoWidget>
#include <phonon/MediaObject>
#include <phonon/MediaSource>
#include <phonon>
#include <QVBoxLayout>
#include <QFileDialog>
#include <QPushButton>
#include <QUrl>
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
QPushButton *quit;
QPushButton *addFile;
QWidget *Main;
Phonon::VideoPlayer *player;
public slots:
void startVideo();
};
my header ^
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
Main = new QWidget;
addFile = new QPushButton("Dodaj Plik");
quit = new QPushButton("Zamknij");
player = new Phonon::VideoPlayer(Phonon::VideoCategory, Main);
QVBoxLayout *layout = new QVBoxLayout;
layout->addWidget(addFile);
layout->addWidget(quit);
layout->addWidget(player);
Main->setWindowTitle("Phonon");
Main->setLayout(layout);
Main->setGeometry(550, 312, 640, 480);
Main->show();
QObject::connect(addFile, SIGNAL(clicked()), player, SLOT(startVideo()));
QObject::connect(quit, SIGNAL(clicked()), Main, SLOT(close()));
}
MainWindow::~MainWindow()
{
}
void MainWindow::startVideo()
{
QString file = QFileDialog::getOpenFileName(this, tr("odtworz film"));
player->play(file);
}
source ^
For now application runs without problems but when I click "dodaj plik" nothing happens and debugger says it have no such a slot like startVideo()
Can you help me to figure out?
The problem is that you establish connection like this:
QObject::connect(addFile, SIGNAL(clicked()), player, SLOT(startVideo()));
however your startVideo() slot defined in the MainWindow class. Thus, the correct connection should look like:
connect(addFile, SIGNAL(clicked()), this, SLOT(startVideo()));
The QObject:: prefix is not needed, as the QMainWindow - the base class, already is QObject.
Related
I'm a Qt newbie, working in Qt Creator 3.1.2 (Ubuntu Linux), Qt 5.3.1.
My program has a form with a button (pushButton) which changes the value of a text field (plainTextEdit) on being pressed. Both pushButton and plainTextEdit have been added in graphical mode. Connection between the button and its slot (on_pushButton_clicked()) has been set up via the graphical interface too.
The problem is, the program produces a bogus plainTextEdit, i.e. a different one, in the upper left corner, where the output goes to, while the "main" one stays clean. The question hence is, how I can avoid it? In general, how should I connect graphical widgets and their counterparts in the code? Here is my program:
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QPushButton>
#include <QPlainTextEdit>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
QPushButton *pushButton;
QPlainTextEdit *plainTextEdit;
};
#endif // MAINWINDOW_H
main.cpp:
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
plainTextEdit = new QPlainTextEdit(this);
// whenever I remove the previous line, I get SIGSEGV
setWindowTitle(tr("My test app..."));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
plainTextEdit->setPlainText("Some text here");
}
It's the widget you're creating in your constructor that is "bogus". The widgets you created in the forms editor belong to the Ui::MainWindow, you must not re-create them in your main window.
Remove this from your MainWindow:
QPushButton *pushButton;
QPlainTextEdit *plainTextEdit;
Remove the widget creation from the constructor:
plainTextEdit = new QPlainTextEdit(this);
Change your on_pushButtonClicked member to:
ui->plainTextEdit->setPlainText("Some text here");
I want to implement simple commands like a qDebug() when I click on a sub menu in the mainwindow. I was referring to sample program given along with the Qt 5 IDE (...\Qt\Qt5.2.0\5.2.0\msvc2010\examples\widgets\mainwindows\menus), and using it, I managed to construct the code. I do not receive any compile time or run time errors.
I created the mainwindow.ui using the design mode. It has an object of the QAction class called actionInterval.
But when I click on it, nothing happens, I am not able to implement the command in void interval(). I guess I am not connecting properly. What am I missing here? Please advise.
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QDebug>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
void createActions();
private slots:
void interval();
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
createActions();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::createActions()
{
ui->actionInterval = new QAction(tr("&Interval"), this);
ui->actionInterval->setStatusTip(tr("Set the interval for capturing delta & reference images"));
connect(ui->actionInterval, SIGNAL(triggered()), this, SLOT(interval()));
}
void MainWindow::interval()
{
qDebug()<<"inside interval qdialog";
}
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
void MainWindow::createActions()
{
ui->actionInterval->setStatusTip(tr("Set the interval for capturing delta & reference images"));
connect(ui->actionInterval, SIGNAL(triggered()), this, SLOT(interval()));
}
You shouldn't need that ui->actionInterval = new QAction(tr("&Interval"), this); line, the ui->setupUi() handles that for you, so it's potentially causing an incorrect reference so when you do click on it it's not firing correctly.
I tried to do a bunch of research on how to solve this problem, and everything is slightly different than my situation, or didn't work to fix my problem. I will start off by explaining my main goal. I have a main window with 7 buttons on it(amongst other things), when you hit each button, it closes out the current window and opens up a new window. All the windows will have the same 7 buttons, so you can go between each window. With all windows having the exact same 7 buttons, I wanted to set up a function that each class can call to set up each button and connect to a slot() in my mainwindow.cpp(called setupSubsystemButtons in example below). The actual buttons are being placed there, but they only work when pressed from my mainwindow.cpp....when I press them from a different class nothing happens.
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QtWidgets>
#include <QDialog>
namespace Ui {
class MainWindow;
}
class MainWindow : public QDialog
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
QWidget *window;
void setupSubsystemButtons(QGridLayout *layout);
~MainWindow();
private:
Ui::MainWindow *ui;
QLineEdit *tempValueBox;
QLineEdit *humidityValueBox;
QLineEdit *c02ValueBox;
...
public slots:
void ECSgeneralScreen();
void homeScreen();
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "ecsgeneralcommand.h"
#include <QtWidgets>
#include <QtCore>
MainWindow::MainWindow(QWidget *parent) : QDialog(parent)
{
QGridLayout *layout = new QGridLayout;
...
setLayout(layout);
}
void MainWindow::ECSgeneralScreen()
{
ECSgeneralCommand *ECSgeneral = new ECSgeneralCommand;
this->close();
ECSgeneral->show();
//opens up the ECS screen
}
void MainWindow::homeScreen()
{
MainWindow *home = new MainWindow;
this->close();
home->show();
//opens up the home screen
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::setupSubsystemButtons(QGridLayout *layout)
{
//Push Button Layout
homeScreenButton = new QPushButton("Home");
layout->addWidget(homeScreenButton, 3, 11);
connect(homeScreenButton, SIGNAL(clicked()), this, SLOT(homeScreen()));
ECSgeneralScreenButton = new QPushButton("General");
layout->addWidget(ECSgeneralScreenButton,5,11);
connect(ECSgeneralScreenButton, SIGNAL(clicked()), this, SLOT(ECSgeneralScreen()));
}
ecsgeneralcommand.h
#ifndef ECSGENERALCOMMAND_H
#define ECSGENERALCOMMAND_H
#include <QDialog>
#include <QMainWindow>
#include <QtWidgets>
#include <QObject>
#include "mainwindow.h"
class ECSgeneralCommand : public QDialog
{
Q_OBJECT
public:
explicit ECSgeneralCommand(MainWindow *parent = 0);
private:
...
public slots:
};
#endif // ECSGENERALCOMMAND_H
ecsgeneralcommand.cpp
#include "ecsgeneralcommand.h"
#include "mainwindow.h"
#include <QtWidgets>
#include <QtCore>
ECSgeneralCommand::ECSgeneralCommand(MainWindow *parent) : QDialog(parent)
{
QGridLayout *layout = new QGridLayout;
QWidget::setFixedHeight(600);
QWidget::setFixedWidth(550);
...
MainWindow setupButtons;
//Setup Subsystem Buttons
setupButtons.setupSubsystemButtons(layout);
setLayout(layout);
};
MainWindow setupButtons;
//Setup Subsystem Buttons
setupButtons.setupSubsystemButtons(layout);
This will create the buttons and connect their signals to slots of setupButtons, which will get deleted as soon as it's out of scope (the end of the ECSgeneralCommand constructor). So your buttons will be left connected to nothing.
You need to connect the button signals to an object that will exist at the time the button is pressed, such as the ECSgeneralCommand itself. Then it could close itself and spawn the correct window.
Or, possibly a much better solution, if applicable for your application: Use a single main window, with a QStackedWidget that switches widgets when a button is pressed. That's what's typically done.
I'm trying to connect a signal from a QProcess inside my mainwindow() object to another QObject based class inside my mainwindow() object but I get this error:
QObject::connect: Cannot connect (null)::readyReadStandardOutput () to (null)::logReady()
Heres the code, its not complete by any means but I don't know why it doesn't work.
exeProcess.h
#ifndef EXEPROCESS_H
#define EXEPROCESS_H
#include <QObject>
class exeProcess : public QObject
{
Q_OBJECT
public:
explicit exeProcess(QObject *parent = 0);
signals:
void outLog(QString outLogVar); //will eventually connect to QTextEdit
public slots:
void logReady();
};
#endif // EXEPROCESS_H
exeProcess.cpp
#include "exeprocess.h"
exeProcess::exeProcess(QObject *parent) :
QObject(parent)
{
}
void exeProcess::logReady(){
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QProcess>
#include "exeprocess.h"
/*main window ---------------------------------------*/
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
QProcess *proc;
exeProcess *procLog;
public slots:
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(proc, SIGNAL(readyReadStandardOutput ()), procLog, SLOT(logReady()));
}
MainWindow::~MainWindow()
{
delete ui;
}
Thanks!.
You need to create the proc and procLog objects.
You've only got pointers as class members, so you'll have to initialize those (with new). connect only works on live objects.
proc is a pointer, but it does not point to anything. You have to instantiate a qprocess before you connect it!
proc = new QProcess();
connect(proc, SIGNAL(readyReadStandardOutput ()), procLog, SLOT(logReady()));
When I try to emit readAllStandardOutput() to a QString im getting an unexpected program crash, even if i connvert the QByteStream to a QString, any idea why that is? heres teh source
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QProcess>
#include <QString>
#include "exeprocess.h"
/*main window ---------------------------------------*/
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
QProcess *proc;
signals:
void outLog(QString outLogVar); //plug this into the QTextEdit box
public slots:
void logReady(); // plug the QProcess into this
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include <QByteArray>
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QProcess *proc = new QProcess; //initialize proc
QStringList arguments;
arguments << "-h";
connect(proc, SIGNAL(readyReadStandardOutput ()), this, SLOT(logReady()));
proc->start("/Applications/Graphics/3Delight-9.0.87/bin/renderdl", arguments);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::logReady(){
QString str = proc->readAllStandardOutput();
emit outLog(str);
}
Thanks!
This line is the problem:
QProcess *proc = new QProcess; //initialize proc
You're shadowing the member variable by reusing that name. When logReady is called, the 'proc' that you call readAllStandardOutput() on is a different (null) pointer and so everything crashes. The fix is simple: replace the above line with
proc = new QProcess;