button clicked to set text in another form

[vanduongbk]

hello everyone
i have a form1 and mainform,
how when i click a button in form1 and a text was set to Qlabel in mainform
examples as when click ok button in form1 and qlabel in mainform was set text "complete transfer"
thank you

[Santosh Reddy]

You will need to use signal and slot to do so. You can read about it here

Connect the clicked() signal of the button in form1 to a slot of the widget/object managing the mainfrom, and in this slot set the text of the QLabel.

[vanduongbk]

You will need to use signal and slot to do so. You can read about it here

Connect the clicked() signal of the button in form1 to a slot of the widget/object managing the mainfrom, and in this slot set the text of the QLabel.

hello,
i put in mainform.h
public slots:
void update_label1(QString string);

in form1.h ,i have consist a include "mainform.h>
and in form1.c ,i use command connect(ui->pushButton,SIGNAL(clicked()),what's here,SLOT(update_label1("text")));
plz me,thank

[nix]

Hi, you can try something like this.

Create a new signal to form1 with

signals:
void transfertCompleted(QString);
 
private slots:
void btnClicked();
 
void form1::btnClicked()
{
   emit(transfertCompleted("your text");
}

signals:
void transfertCompleted(QString);

private slots:
void btnClicked();

void form1::btnClicked()
{
   emit(transfertCompleted("your text");
}

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In form1 constructor connect the button's clicked signal to the btnClicked slot.

Now in the mainform, after creating form1 add :

connect(form1, SIGNAL(transfertCompleted(QString)), this, SLOT(update_label1(QString)))

connect(form1, SIGNAL(transfertCompleted(QString)), this, SLOT(update_label1(QString)))

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If you donc have to send text from form1 to mainwindow you can avoid using the slot btnClicked() and just connecting both signals directly.

[vanduongbk]

hi nix, i dont know what is emit
and you can a demo code for void transfertCompleted(QString)

in form1,i have a private slot as:
void form1::on_pushButton_clicked()
{
//some a calculate and write a data ro uart here
//i want to write text to mainform
}

i want to do that when i click button ,it will send data to uart and in mainform ,qlabel text is set as "sent complete"
thank

[nix]

First, you should really read some Qt doc about Signals and Slots, there is link is in a previous message. It's the most important thing in Qt, so be sure it's not a waste a time.

transfertCompleted(QString) is not a method and doesn't have any code : it's a signal.
emit() is a qt fonction that "emit" (or raise) the signal, then Qt will internaly search all slots connected to that signal and execute them.

[vanduongbk]

hello,i execute as:

in form1,i have a private slot as:
void form1:n_pushButton_clicked()
{
//some a calculate and write a data ro uart here
//i want to write text to mainform
emit(transfertCompleted("your text");
}

in mainform ,i set slot as:
public slots:
void update_label1(const QString &string);

void mainfor::update_label1(const QString &string)
{
ui->label_channel1->clear();
ui->label_channel1->setText(string);
}

and in mainform, connect(form1, SIGNAL(transfertCompleted(QString)), this, SLOT(update_label1(QString)))
when execute ,it not have error but release error as :The program has unexpectedly finished
plz help me

[nix]

Use Code Tag please, the code is just not readable the way you did.

Can you run in debug mode with the debugger in order to get a backtrace.

Can you post the complete code for those two classes.

[vanduongbk]

this is my code ,please help me:
mainform.h

#ifndef MAINFORM_H
#define MAINFORM_H

#include <QMainWindow>
#include "form1.h"

namespace Ui {
class mainform;
}

class mainform : public QMainWindow
{
Q_OBJECT

public:
explicit mainform(QWidget *parent = 0);
~mainform();

public slots:
void update_label(const QString &string);

private:
Ui::mainform *ui;
};

#endif // MAINFORM_H

mainform.cpp

#include "mainform.h"
#include "ui_mainform.h"

mainform::mainform(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::mainform)
{
ui->setupUi(this);
connect(form1, SIGNAL(transfertCompleted(QString)), this, SLOT(update_label(QString)))
}

mainform::~mainform()
{
delete ui;
}

void mainform::update_label(const QString &string)
{
ui->label->clear();
ui->label->setText(string);
}

form1.h

#ifndef FORM1_H
#define FORM1_H

#include <QDialog>

namespace Ui {
class form1;
}

class form1 : public QDialog
{
Q_OBJECT

signals:
void transfertCompleted(QString);
public:
explicit form1(QWidget *parent = 0);
~form1();

private slots:
void on_pushButton_clicked();

private:
Ui::form1 *ui;
};

#endif // FORM1_H

form1.cpp

#include "form1.h"
#include "ui_form1.h"

form1::form1(QWidget *parent) :
QDialog(parent),
ui(new Ui::form1)
{
ui->setupUi(this);
}

form1::~form1()
{
delete ui;
}

void form1:n_pushButton_clicked()
{
//write data
//i want when click it send data and also send text to mainform
emit(transfertCompleted("transfer complete");
}

[nix]

Some code is missing, where form1 is created and shown? I think you should move the line

connect(form1, SIGNAL(transfertCompleted(QString)), this, SLOT(update_label(QString)))

connect(form1, SIGNAL(transfertCompleted(QString)), this, SLOT(update_label(QString)))

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just after you create the object, and not on the mainwindow constructor.

This is my mainwindow.c code and it works, other files are identitcals too yours at the first look.

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#include <form1.h>
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(openWindow()));
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::openWindow()
{
    Form1 *form = new Form1(this);
    connect(form, SIGNAL(transfertCompleted(QString)), this, SLOT(updateLabel(QString)));
    form->show();
}
 
void MainWindow::updateLabel(QString text)
{
   ui->label->clear();
   ui->label->setText(text);
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <form1.h>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(openWindow()));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::openWindow()
{
    Form1 *form = new Form1(this);
    connect(form, SIGNAL(transfertCompleted(QString)), this, SLOT(updateLabel(QString)));
    form->show();
}

void MainWindow::updateLabel(QString text)
{
   ui->label->clear();
   ui->label->setText(text);
}

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Note : the code tag is not the one you used ;-)

[vanduongbk]

thank you
but my pushbutton is in form1 ,no mainwindow
i only have qlabel with a name is lable in mainwindow
can not use ui->pushButton in mainwindow