Weird problem, with MainWindow class variables.
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I ran into something similar to this recently when trying to update a value by reference. In my case it was done this way for a very different reason but otherwise it was similar to what you are doing.
I would suggest you re-write your access functions like this:
@
int MainWindow::GetImageHeight(void) {return imageHeight;}
int MainWindow::GetImageWidth(void) {return imageWidth; }
@You can use them like this:
@
MainWindow mw;
int width, height;height = mw.GetImageHeight(); width = mw.GetImageWidth();@
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In your code you have this:
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QApplication a(argc, argv);
MainWindow w;
Own own;
...
@These exist only in main() which will run until a.exec() returns. For the classes 'w' and 'own' is there a pointer, or some other reference to these classes that you can use outside of main()?
For this code:
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MainWindow mw;
int width, height;height = mw.GetImageHeight(); width = mw.GetImageWidth();@
GetImageHeight() and GetImageWidth() should return zero or possibly some other random value as it is another, unrelated class.
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In your example (below), are you trying to get width and height from MainWindow before app.exec() ?
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MainWindow mw;
int width, height;mw.GetImageHeight(height); mw.GetImageWidth(width);@
If so then MainWindow::imageHeight and imageWidth are not initialized and you are getting whatever random numbers are there.
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I post my full source code here
mainwindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include "networking.h"
namespace Ui {
class MainWindow;
}class MainWindow : public QMainWindow
{
Q_OBJECTpublic:
explicit MainWindow(QWidget *parent = 0); void GetImageHeight(int &height); void GetImageWidth(int &width); ~MainWindow();private slots:
void on_pushButton_clicked(); void on_WidthSlider_valueChanged(int value); void on_HeightSlider_valueChanged(int value);private:
int imageWidth;
int imageHeight;QUrl q; Ui::MainWindow *ui;};
#endif // MAINWINDOW_H
@
networking.h
@
#ifndef NETWORKING_H
#define NETWORKING_H#include <QtNetwork/QNetworkAccessManager>
#include <QtNetwork/QNetworkRequest>
#include <QMessageBox>
#include "mainwindow.h"class networking : public QObject
{
Q_OBJECTpublic: networking(); void on_download_triggered(QUrl url); bool IsNetworkAvailable(); private: QNetworkAccessManager *manager = new QNetworkAccessManager(this); void ProcessPicture(QImage *image);private slots:
void onNetworkReply(QNetworkReply* reply);};
#endif // NETWORKING_H
@
mainwindow.cpp
@#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{ui->setupUi(this); this->setFixedSize(378, 304);}
MainWindow::~MainWindow()
{
delete ui;
}void MainWindow::on_pushButton_clicked()
{if(ui->URLbox->text().isEmpty()) QMessageBox::information(0, "Warning", "No URL inserted!"); else { networking *n = new networking(); q = ui->URLbox->text(); if(n->IsNetworkAvailable()) n->on_download_triggered(q); }}
void MainWindow::GetImageHeight(int &height) {height = imageHeight;}
void MainWindow::GetImageWidth(int &width) {width = imageWidth; }
void MainWindow::on_WidthSlider_valueChanged(int value)
{
imageWidth = value;
QString valueString = QString::number(value);
ui->WidthLabel->setText(valueString);
}void MainWindow::on_HeightSlider_valueChanged(int value)
{
imageHeight = value;
QString valueString = QString::number(value);
ui->HeightLabel->setText(valueString);
}@
networking.cpp
@#include "networking.h"
#include <QtNetwork/QNetworkReply>
#include <QFileDialog>networking::networking()
{
connect(manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(onNetworkReply(QNetworkReply*)));
}
void networking::on_download_triggered(QUrl url)
{
manager->get(QNetworkRequest(QUrl(url)));
}void networking::ProcessPicture(QImage *image)
{
MainWindow *mw = new MainWindow();int width, height; mw->GetImageHeight(height); mw->GetImageWidth(width); qDebug() << height; qDebug() << width; QImage newimage = image->scaled(width, height, Qt::KeepAspectRatio); QString path = QFileDialog::getSaveFileName(0, tr("Save Image"), "C://", tr("Image Files (*.png *.jpg *.bmp)")); newimage.save(path);}
void networking::onNetworkReply(QNetworkReply* reply)
{
if(!reply->error())
{
QImage *img = new QImage();
img->loadFromData(reply->readAll());if(img->isNull()) QMessageBox::critical(0, "Error", "Inserted URL is not an image!"); ProcessPicture(img); } else { QVariant statusCode = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute); int status = statusCode.toInt(); qDebug() << status; switch(status) { case 0: { QMessageBox::critical(0, "Error", "URL doesn't exist!"); break; } case 404: { QMessageBox::critical(0, "Error", "404 not found!"); break; } } }}
bool networking::IsNetworkAvailable()
{
QNetworkAccessManager m;
QNetworkReply *check = m.get(QNetworkRequest(QUrl("google.com")));
return (!check->error()) ? true : false;
}
@ -
I think this is your problem:
@
void networking::ProcessPicture(QImage *image)
{
MainWindow *mw = new MainWindow();int width, height; mw->GetImageHeight(height); mw->GetImageWidth(width); qDebug() << height; qDebug() << width;...
}
@The class '*mw' is unrelated to the mw class created in main(). The member imageWidth and imageHeight are not updated in this version.
To verify this you could create a global pointer of the MainWindow class and see if this solves the problem:
@
MainWindow *g_mw;int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; Own own; g_mw = &mw; QObject::connect(&w, SIGNAL(heightValueChanged(int)), &own, SLOT(imageHeight(int))); QObject::connect(&w, SIGNAL(widthValueChanged(int)), &own, SLOT(imageWidth(int))); w.show(); return a.exec(); }@
and then in your network module
@
#include "networking.h"
#include <QtNetwork/QNetworkReply>
#include <QFileDialog>extern MainWindow *g_mw;
networking::networking()
{
...
}
...
void networking::ProcessPicture(QImage *image)
{
// MainWindow *mw = new MainWindow();int width, height; g_mw->GetImageHeight(height); g_mw->GetImageWidth(width); qDebug() << height; qDebug() << width;...
}
@Note: I wouldn't use a global variable like this. You are better to pass a pointer (maybe as part of the constructor of your Networking class?). It is just a simple way to verify this is the problem without changing too much.
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Rondog is right. You are creating new MainWindow object and it is not related to your main MainWindow.
Another option to solve it would be to pass a MainWindow pointer to networking ctor and keep it there. Then in networking::ProcessPicture() use that pointer.
networking.h@
#ifndef NETWORKING_H
#define NETWORKING_Hclass MainWindow; class networking : public QObject {...
public:
networking(MainWindow* mw);...
private:
MainWindow* m_mw;}; #endif // NETWORKING_H@
networking.cpp
@
#include "networking.h"
#include "MainWindow.h"
#include <QtNetwork/QNetworkReply>
#include <QFileDialog>networking::networking(MainWindow* mw) : m_mw(mw) {...
}void networking::ProcessPicture(QImage *image)
{
// MainWindow *mw = new MainWindow();int width, height; m_mw->GetImageHeight(height); m_mw->GetImageWidth(width); qDebug() << height; qDebug() << width;...
}
@