#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <Phonon/MediaSource>
#include <QUrl>
#include <Phonon/MediaObject>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
QUrl url("http://www.example.com/music.ogg");
Phonon::MediaObject *wow =
Phonon::createPlayer(Phonon::NoCategory,
Phonon::MediaSource(url));
wow->play();
}
This code won't play the file, and I'm getting this error:
:: error: collect2: ld returned 1 exit status
Can anyone help me get the file to play when I click the button?
Thanks.
I guess that there are one or more functions declared in the header file but their bodies haven't been built yet.
for example:
//headerfile
class MyClass
{
public: MyClass();
private: void function1();
void function2();
};
//source file
MyClass::MyClass(){}
void MyClass::function1(){ /*do something*/ }
//here function2 is missing.
So, please check that all the functions in the whole project have their bodies.
For a basic phonon media player,
#ifndef MYVIDEOPLAYER_H
#define MYVIDEOPLAYER_H
#include <QWidget>
#include <QPushButton>
#include <Phonon/VideoPlayer>
#include <QVBoxLayout>
class MyVideoPlayer : public QWidget
{
Q_OBJECT
public:
explicit MyVideoPlayer(QWidget *parent = 0);
private:
Phonon::VideoPlayer *videoPlayer;
QPushButton *btnButton;
QVBoxLayout layout;
private slots:
void onPlay();
};
#endif // MYVIDEOPLAYER_H
#include "myvideoplayer.h"
MyVideoPlayer::MyVideoPlayer(QWidget *parent) :
QWidget(parent)
{
videoPlayer=new Phonon::VideoPlayer(Phonon::VideoCategory,this);
btnButton=new QPushButton("Play",this);
layout.addWidget(btnButton);
layout.addWidget(videoPlayer);
setLayout(&layout);
connect(btnButton,SIGNAL(clicked()),this,SLOT(onPlay()));
}
void MyVideoPlayer::onPlay()
{
videoPlayer->load(Phonon::MediaSource("movie.mp4"));
videoPlayer->play();
}
As templatetypedef commented, it sounds like a linker error. Ensure that you have added all of the necessary libraries to the .pro file. For example, you need to link against Phonon, so your .pro file must contain
QT += phonon
Related
I am trying to download a txt file from a url in QT but i can't seem to make it work.
I am following this guide https://wiki.qt.io/Download_Data_from_URL. I implemented the filedownloader class exactly like it's made in the guide, but when i try to use it like specified in the guide I cannot make it work. I created a slot to be called when the download is finished, but if i try to call the downloader inside like the guide it says it is an undeclared identifier.
Does anyone know how to correctly implement this code?
this is the .cpp of my code
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "mainwindow.h"
#include <QStringList>
#include <QCoreApplication>
#include <QFile>
#include <QFileInfo>
#include <QList>
#include <QtNetwork/QNetworkReply>
#include <QStringList>
#include <QTimer>
#include <QUrl>
#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkRequest>
#include <filedownloader.h>
#include <iostream>
#include <QObject>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
QUrl emiurl( "url of my file");
// call to the downloader class.In the guide it's made differently, but it doesn't work
FileDownloader emiload(emiurl,this);
//this connect links the end of the download with the textwriter slot
QObject::connect(&emiload, SIGNAL (downloaded()), this, SLOT (textwriter()));
}
>MainWindow::~MainWindow()
{
delete ui;
}
//slot needed to create the txt file from the downloaded one
void MainWindow::textwriter()
{
QByteArray emibyte;
emibyte=emiload->downloadedData(); //this line gives me error
QFile emifile("emi.txt");
emifile.open(QIODevice::WriteOnly);
std::cout << emibyte.size() << std::endl;
QDataStream out(&emifile);
out << emibyte;
std::cout << emifile.size() << std::endl;
}
Now here's the .h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include "filedownloader.h"
#include <QMainWindow>
#include <QtNetwork/QNetworkAccessManager>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private:
Ui::MainWindow *ui;
private slots:
void textwriter();
};
#endif // MAINWINDOW_H
To make the undeclared identifier go away and successfully compile, you need to add FileDownloader to the class' declaration. This way, it will be known throughout the class.
I chose to go with the approach that's usual in Qt, to declare a pointer to FileDownloader.
#pragma once // <--- this is supported by virtually any compiler today
#include <QMainWindow>
#include <QtNetwork/QNetworkAccessManager>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class FileDownloader; // <-- forward declaration is enough, but you can also #include "filedownloader.h"
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget* parent = nullptr);
~MainWindow();
private:
Ui::MainWindow* ui = nullptr;
FileDownloader* emiload = nullptr; // <--- the important line!
private slots:
void textwriter();
};
And then instantiate and call emiload in the constructor:
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
// create an instance of FileDownloader with "new".
emiload = new FileDownloader(QUrl("url of my file"), this);
// using member pointer connection available since Qt5
connect(emiload, &FileDownloader::downloaded, this, &MainWindow::textwriter);
}
OK, let's start again...
I've created an project (Qt Widget Application) with Qt Creator.
My project structure:
myproject.pro
Headers
dialogform.h
mainwindow.h
Sources
dialogform.cpp
main.cpp
mainwindow.cpp
Forms
dialogform.h
mainwindow.h
When I click on DialogForm pushbutton, I need to call the clear() function from MainWindow
In my code below, my project is running, but, the clear() function does not clear the lineedit.
Do anyone known how can i fix this?
Thank you very much!
dialogform.h
#ifndef DIALOGFORM_H
#define DIALOGFORM_H
#include <QDialog>
namespace Ui {
class DialogForm;
}
class DialogForm : public QDialog
{
Q_OBJECT
signals:
void clearMainWindow();
public:
explicit DialogForm(QWidget *parent = 0);
~DialogForm();
private slots:
void on_pbClearLineEdit_clicked();
private:
Ui::DialogForm *ui;
};
#endif // DIALOGFORM_H
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void clear();
private slots:
void on_pbCallDialog_clicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
dialogform.cpp
#include "dialogform.h"
#include "ui_dialogform.h"
#include "mainwindow.h"
DialogForm::DialogForm(QWidget *parent) :
QDialog(parent),
ui(new Ui::DialogForm)
{
ui->setupUi(this);
}
DialogForm::~DialogForm()
{
delete ui;
}
void DialogForm::on_pbClearLineEdit_clicked()
{
connect(); // need help here. I'm using Qt 5.6.1
}
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"
#include "dialogform.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pbCallDialog_clicked()
{
DialogForm *dialogForm = new DialogForm(this);
dialogForm->show();
}
void MainWindow::clear()
{
ui->lineEdit->clear();
}
myfunction accesses an attribute of class myfile. Therefore it either needs to be a method of myfile as well, or it could be a friend function of the class myfile. In the latter case, however, you would need to give the relevant instance of myfile to myfunction as an argument. All usages of myfunction would need to be updated in either case.
The solution:
DialogForm::DialogForm(QWidget *parent) :
QDialog(parent),
ui(new Ui::DialogForm)
{
ui->setupUi(this);
connect(ui->pbClearLineEdit, &QPushButton::clicked, static_cast<MainWindow*>(parent), &MainWindow::clear);
}
I am trying to access the ui elements of different class but getting error message. I've tried to do this for many hours but still failing, I feel that I am missing something simple.
I am trying to access an element "label" which is in form.h
mainwindow:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "form.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
Form * elemForm = new Form(this);
elemForm->ui; // works
//elemForm->ui->label; // does not work
}
MainWindow::~MainWindow()
{
delete ui;
}
form.h
#ifndef FORM_H
#define FORM_H
#include <QWidget>
namespace Ui {
class Form;
}
class Form : public QWidget
{
Q_OBJECT
public:
explicit Form(QWidget *parent = 0);
~Form();
Ui::Form *ui;
private:
};
#endif // FORM_H
form.cpp
#include "form.h"
#include "ui_form.h"
Form::Form(QWidget *parent) :
QWidget(parent),
ui(new Ui::Form)
{
ui->setupUi(this);
ui->label; //works fine here
}
Problem is in mainwindow file. I know this is inappropriate code, I'm just interested what I'm doing wrong. I am struggling to find whats wrong, any ideas?
In addition to form.h, you should also include ui_form.h in your MainWindow.h.
That's because the form elements are all defined in Ui::Form which is accessible by including :
#include "ui_form.h"
Please, try to think on what are you doing, and how to do things better.
Don't feel think that method explained by Nejat is controversial to OOP? If you are trying to use OOP, learn how to do it and use it.
To get deeper understanding on what am I talking about, please, read this short story about encapsulation.
Back to your example. Here is clean, simple and easy way to do what you want:
Your mainwindow.h:
#include "mainwindow.h"
#include "ui_mainwindow.h"
// Include only header of your Form, not ui_form.h!
#include "form.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
Form* elemForm = new Form(this);
// Use public method of your Form object!
elemForm->changeUI();
}
Your form.h:
#include <QWidget>
namespace Ui {
class Form;
}
class Form : public QWidget
{
Q_OBJECT
public:
explicit Form(QWidget *parent = 0);
~Form();
void changeUI(); // here you can do all what you want with your UI
private:
Ui::Form *ui;
};
in form.cpp you'll have realization:
void Form::changeUI()
{
ui->... // do all what you want with UI
}
I have a QTabWidget which contains a QPlainTextEdit. I have managed to add action to the QTabWidget so that whenever a new tab opens, a new QPlainTextEdit is also added in the new tab. See code.
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPlainTextEdit>
#include <QMessageBox>
#include <QAction>
#include <QTextCursor>
#include <iostream>
#include <QKeyEvent>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
setWindowTitle("Tilde");
current_tab = 1;
on_action_New_triggered();
ui->tabWidget->setTabsClosable(true);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_action_New_triggered()
{
QString newTab = "Tab " + QString::number(current_tab);
ui->tabWidget->addTab(new QPlainTextEdit, newTab);
ui->tabWidget->setCurrentIndex(current_tab - 1);
current_tab++;
editor = qobject_cast<QPlainTextEdit *>(ui->tabWidget->currentWidget());
editor->setFocus();
/*connect(editor->document(), SIGNAL(cursorPositionChanged(QTextCursor)),
this, SLOT(on_editor_cursorPositionChanged()));*/
}
void MainWindow::on_actionNew_document_triggered()
{
on_action_New_triggered();
}
void MainWindow::on_action_Exit_triggered()
{
QMessageBox msg;
msg.addButton(QMessageBox::Yes);
msg.addButton(QMessageBox::No);
msg.setText("Exit program?");
int selection = msg.exec();
if (selection == QMessageBox::Yes)
qApp->exit(0);
}
// highlight current line
void MainWindow::on_editor_cursorPositionChanged()
{
QTextEdit::ExtraSelection highlight;
highlight.cursor = editor->textCursor();
highlight.format.setProperty(QTextFormat::FullWidthSelection, true);
highlight.format.setBackground( QColor(240, 246, 217) );
QList<QTextEdit::ExtraSelection> extras;
extras << highlight;
editor->setExtraSelections(extras);
}
The commented code gives compiler error:
QMetaObject::connectSlotsByName: No matching signal for
on_editor_cursorPositionChanged()
I have added the function in the header file.
Header file:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QPlainTextEdit>
#include <QTextCursor>
namespace Ui
{
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_action_New_triggered();
void on_actionNew_document_triggered();
void on_action_Exit_triggered();
void on_editor_cursorPositionChanged();
private:
Ui::MainWindow *ui;
QPlainTextEdit *editor;
qint8 current_tab;
};
#endif // MAINWINDOW_H
Could it be that your signature for the SLOT is wrong?
/*connect(editor->document(), SIGNAL(cursorPositionChanged(QTextCursor)),
this, SLOT(on_editor_cursorPositionChanged()));*/
Should be?
connect(editor->document(), SIGNAL(cursorPositionChanged(QTextCursor)),
this, SLOT(on_editor_cursorPositionChanged(QTextCursor)));
Also, the naming convention you are using for that slot might be conflicting here with your manual connection. Qt may be trying to use the connectSlotsByName mechanism on your SLOT by matching the name: on_<member>_<signal>
In this case, the current signature of that SLOT on_editor_cursorPositionChanged() would match with the QPlainTextEdit editor member. And then you are manually connecting the document to it with the wrong signature. You probably should create another slot that is named more normally docCursorPosChanged(QTextCursor)
This question should hopefully be easy to answer. I created a few buttons in my MainWindow using Qt Creator, and when I go to write the functions for the buttons, the compiler says they were not declared in this scope. What do I need to #include for these objects to be declared? The compiler error for the following would be 'baseDir' was not declared in this scope. baseDir is the objectName for a lineEdit in my window.
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "ui_mainwindow.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void getDir();
void createProj();
private slots:
void on_findDir_clicked();
void on_create_clicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "functions.h"
#include <QtGui/QApplication>
#include <QFileDialog>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_findDir_clicked()
{
QString path;
path = QFileDialog::getOpenFileName(
this,
"Choose a file to open",
QString::null,
QString::null );
baseDir->setText( path );
}
The items you define in your .ui file are not added directly to your main window class, they are added to its ui membre.
Try with:
ui->baseDir->setText( path );
Look at the ui_mainwindow.h file that is generated during the build if you're curious.