C ++-从QPushButton将项目添加到QListWidget

Question

Hello I am trying to add items to a QListWidget from a QPushButton. Both the QListWidget and QPushButton are added as individual widgets inside of a QGraphicsScene. I want the effect of a box that fills with text lines

main.c

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;

    QGraphicsView view;

    QGraphicsScene *scene = new QGraphicsScene(0, 0, 1200, 1200, &view);

    scene->setBackgroundBrush(Qt::gray);

    view.setScene(scene);

    QPushButton *PushButton1;
    PushButton1 = new QPushButton();
    PushButton1->setGeometry(QRect(19, 20, 154, 4));

    QListWidget *ListWidget;
    ListWidget = new QListWidget;

    scene->addWidget(ListWidget);
    scene->addWidget(PushButton1);

    QObject::connect(PushButton1, SIGNAL(clicked()),&w, SLOT(handleClick(*QListWidget)));

    view.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);
}

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


void MainWindow::handleClick(QListWidget *List)
{
    int test;

    List->addItem("TESTING");

    //QApplication::quit();

}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QListWidget>


namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

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

private:
    Ui::MainWindow *ui;


    private slots:


    public slots:

        void handleClick(QListWidget *List);
};

#endif // MAINWINDOW_H

This code compiles fine. How I get the following error in the console when the application is running

QObject::connect: No such slot MainWindow::handleClick(*ListWidget) in ..\MenuTest\main.cpp:48

Can someone help me do this? I've seen several tutorials but it's using the designer to make the GUI and I'd like to know how to do it in code without using designer. Thanks.

Answer 1

Your slot accepts QListWidget but you're connecting with ListWidget as the parameter, the signature has to be an exact match due to the way signals and slots work in Qt.

Put handleClick under public slots: and change this line:

QObject::connect(PushButton1, SIGNAL(clicked()),&w, SLOT(handleClick(*ListWidget)));

To this:

QObject::connect(PushButton1, SIGNAL(clicked()),&w, SLOT(handleClick(*QListWidget)));

Update:

I see I missed a key point, the signatures have to match, as in parameter to parameter, so the line up there will not work.

To fix this remove the parameter completely, since PushButton1 can't send it automatically.

QObject::connect(PushButton1, SIGNAL(clicked()),&w, SLOT(handleClick()));

Also remove it here:

void MainWindow::handleClick()

To access the QListWidget you'll have to reference it directly, either by passing it to MainWindow's constructor or iterating the window's controls.