How to reuse the same window after clicking on other button? - qt

Question

I am trying to create an image viewer with slide show. When the user clicks on the play button, the viewer starts to show images. When the the user clicks on the stop button, the viewer stops to show images. After stopping, when the user clicks on the play button again, the viewer will continue to show the remaining images. My problem is that when the user clicks on the stop button and click on the play button again, I don't know how to reuse the same window created at the beginning to show the remaining images.
Button3 is the play button.
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QFileSystemModel>
#include "showpic.h"
#include <QBasicTimer>
#include <QTimer>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_pushButton_3_clicked();
void tick();
void on_pushButton_4_clicked();
private:
Ui::MainWindow *ui;
QFileSystemModel *model;
QString filesPath;
ShowPic *showpic;
QStringList filenames;
QStringList::const_iterator m_imageIt;
QTimer m_timer;
};
#endif // MAINWINDOW_H
showpic.h
#ifndef SHOWPIC_H
#define SHOWPIC_H
#include <QWidget>
namespace Ui {
class ShowPic;
}
class ShowPic : public QWidget
{
Q_OBJECT
public:
explicit ShowPic(QWidget *parent = 0);
~ShowPic();
private:
Ui::ShowPic *ui;
public:
void addPixmap(const QPixmap &pixmap);
};
#endif // SHOWPIC_H
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<QFileDialog>
#include<QFileSystemModel>
#include<QStringList>
#include <QTreeView>
#include <QGraphicsScene>
#include <QTime>
#include <QDebug>
#include <iostream>
#include <QTimer>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
filenames.append("C:\\test\\image.jpg");
filenames.append("C:\\test\\apple.jpg");
filenames.append("C:\\test\\orange.jpg");
filenames.append("C:\\test\\lemon.jpg");
filenames.append("C:\\test\\grape.jpg");
m_timer.setInterval(1000);
connect(&m_timer, SIGNAL(timeout()), this, SLOT(tick()));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::tick(){
showpic->addPixmap(*m_imageIt);
m_imageIt ++;
if(m_imageIt == filenames.end()){
m_timer.stop();
m_imageIt = filenames.begin();
}
}
void MainWindow::on_pushButton_3_clicked() //click on the play button
{
if(!filenames.isEmpty()){ // initial click
showpic = new ShowPic();
m_timer.start();
showpic->setWindowState(Qt::WindowMaximized);
showpic->show();
} else if( ) { // click on the play button again,
m_timer.start(); //???
showpic->setWindowState(Qt::WindowMaximized); //???
showpic->show(); //???
}
}
void MainWindow::on_pushButton_4_clicked() // click on the stop button
{
m_timer.stop();
}
showpic.cpp
#include "showpic.h"
#include "ui_showpic.h"
ShowPic::ShowPic(QWidget *parent) :
QWidget(parent),
ui(new Ui::ShowPic)
{
ui->setupUi(this);
ui->graphicsView->setScene(new QGraphicsScene);
ui->horizontalLayout->addWidget(ui->graphicsView);
this->setLayout(ui->horizontalLayout);
}
ShowPic::~ShowPic()
{
delete ui;
}
void ShowPic::addPixmap(const QPixmap &pixmap){
ui->horizontalLayout->addWidget(ui->graphicsView);
this->setLayout(ui->horizontalLayout);
ui->graphicsView->setScene(new QGraphicsScene);
ui->graphicsView->scene()->addPixmap(pixmap);
ui->graphicsView->fitInView(ui->graphicsView->scene()->itemsBoundingRect() ,Qt::KeepAspectRatio);
}

Answer 1

Else part of on_pushButton_3_clicked won't run in any case because filenames is being filled when MainWindow created. In your code, you're creating new showpic in every click.
Firstly, set showpic to NULL in constructor of MainWindow;
showpic = NULL;
And change on_pushButton_3_clicked method like this;
void MainWindow::on_pushButton_3_clicked() //click on the play button
{
if(showpic == NULL){
showpic = new ShowPic();
}
if(!showpic->isVisible()){
showpic->setWindowState(Qt::WindowMaximized);
showpic->show();
}
m_timer.start();
}
Lastly, i don't have QT now, so my answer may contains typo/syntax error.

Answer 2

This works for me. I tested the scene clearing method, and it worked fine for me. But here I decided to just store the pointer to the QGraphicsPixmapItem as a member variable, and just set a new pixmap to it, instead of clearing the scene constantly. Seems more elegant like this to me.
#include <QtWidgets>
class SlideView : public QWidget
{
Q_OBJECT
public:
SlideView(QWidget *parent = nullptr) : QWidget(parent)
{
setLayout(new QHBoxLayout);
layout()->addWidget(&view);
view.setScene(new QGraphicsScene(this));
pixmap_item = new QGraphicsPixmapItem;
view.scene()->addItem(pixmap_item);
}
void setPixmap(const QPixmap &pixmap)
{
pixmap_item->setPixmap(pixmap);
view.fitInView(view.scene()->itemsBoundingRect(), Qt::KeepAspectRatio);
}
private:
QGraphicsView view;
QGraphicsPixmapItem *pixmap_item = nullptr;
};
class MainWidget : public QWidget
{
Q_OBJECT
public:
MainWidget(QWidget *parent = nullptr) : QWidget(parent)
{
slide_iterator = slides.begin();
setLayout(new QHBoxLayout);
QPushButton *play_button = new QPushButton("Play");
QPushButton *stop_button = new QPushButton("Stop");
layout()->addWidget(play_button);
layout()->addWidget(stop_button);
connect(play_button, &QPushButton::clicked, this, &MainWidget::play);
connect(stop_button, &QPushButton::clicked, this, &MainWidget::stop);
connect(&timer, &QTimer::timeout, this, &MainWidget::showNextSlide);
}
public slots:
void play() {timer.start(1000); view.showMaximized(); view.activateWindow();}
void stop() {timer.stop();}
void showNextSlide()
{
QPixmap pixmap(*slide_iterator);
view.setPixmap(pixmap);
slide_iterator++;
if(slide_iterator == slides.end())
slide_iterator = slides.begin();
}
private:
QTimer timer;
QStringList slides{"one.png", "two.png", "three.png"};
QStringList::const_iterator slide_iterator;
SlideView view;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWidget w;
w.show();
return a.exec();
}
#include "main.moc"