CODEWITHSUNDEEP
c++qt
kubizen
kubizen

Reputation: 25

Connect and pass data between widget and mainwindow

I want to pass data between MainWindow and Widget where I draw graph. In MainWindow I load a data, do few things and create dynamic array.

  1. I need to pass this array from mainwindow to widget to draw a graph.
  2. In widget file I have a function that works, when I click a button in MainWindow

I don't know how to do this between two files mainwindow.cpp and drawwidget.cpp

This is my Code:

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <fstream>
#include <iostream>
#include <iomanip>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    wyczyscpkt(Tab_pkt);
    wyczysc(Tab_we);
    delete ui;
}

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();

signals:


private slots:
void on_saveimageButton_clicked();
    //other functions

public slots:

private:
    Ui::MainWindow *ui;
    //my functions

 public slots:

};

#endif // MAINWINDOW_H

drawwidget.cpp:

DrawWidget::DrawWidget(QWidget *parent) :
    QWidget(parent)
{

}

void DrawWidget::paint(QPainter &painter, struct *myarray) //here I need pass array from mainwindow.cpp
{
 //drawing function
}
void DrawWidget::savePng()
{
 //save image function
}

drawwidget.h:

#ifndef DRAWWIDGET_H
#define DRAWWIDGET_H

#include <QWidget>
#include "mainwindow.h"


class DrawWidget : public QWidget
{
    Q_OBJECT
public:
    explicit DrawWidget(QWidget *parent = 0);

protected:
    void paintEvent(QPaintEvent *);
    void paint(QPainter &painter);
    void savePng();

};

#endif // DRAWWIDGET_H

Upvotes: 1

Views: 4276

Answers (2)

wuarmin
wuarmin

Reputation: 4005

You have to include

#include "drawwidget.h"

your DrawWidget in MainWindow. After that you can instantiate a DrawWidget Object and use it.

Upvotes: 0

talamaki
talamaki

Reputation: 5472

You can use signals and slots in passing data between two QObject based classes (like QMainWindow and QWidget) which don't know anything about each other.

  1. You need to connect your MainWindow signal with your DrawWidget slot. When you emit the signal in MainWindow the DrawWidget object will receive the struct in its slot. Note that you need to register your own struct type with Q_DECLARE_METATYPE in order to pass it in a signal parameter.
  2. Similarly, you can connect your button's clicked signal with a slot method in DrawWidget which you want to trigger when the button is clicked.

Example:

typedef struct
{
} MyStruct; 

Q_DECLARE_METATYPE(MyStruct);

class MainWindow : public QMainWindow
{
    Q_OBJECT
signals:
    void dataChanged(const MyStruct &struct);
};

class DrawWidget : public QWidget
{
    Q_OBJECT
public slots:
    void handleData(const MyStruct &struct);
};

Let's say you instantiate your objects in your main(). You can connect the MainWindow signal to DrawWidget slot like this:

MainWindow m;
DrawWidget d;
QObject::connect(&m, SIGNAL(dataChanged(const MyStruct &)),
                 &d, SLOT(handleData(const MyStruct &)));

When you have your data ready in your MainWindow you emit the signal with the data struct as a parameter.

There is a good explanation of signals and slots here.

Upvotes: 2

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