Can a QListView detect a specific QString and therefore automatically trigger a slot? - qt

Question

I have a specific string on a QLineEdit, this string is passed to a QListView via QPushButton. Those strings are choices of a QComboBox and they are very specific:
1) "[ INFO] Minimum Distance: 5",
2) "[ INFO] Minimum Distance: 10" and
3) "[ INFO] Minimum Distance: 15"
Here a perfectly working minimal verifiable example if you need to test it.
Currently I can successfully change the color of the QGraphicsView but by clicking or double-clicking on the QString entered in the QListView.
The problem: How can I detect the specific QString content inside a QListView in order to change the background color of a QGraphicsView?
What I mean I don't want to click or double-click on the entry of the QListView but I would like the QListView to see that there is a string "[ INFO] Minimum Distance: 5" and therefore change the color of the QGraphicsView automatically without me clicking or double-clicking on the QListView entry.
After I "Go to slot" my choices are the following below:
Below the MVE working code, you can copy /paste on your machine and it will work:
mainwindow.h
#include <QMainWindow>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsTextItem>
#include <QStringListModel>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
void changeColorDetection();
void updateListView();
void updateListView(const QString & message);
private slots:
void on_pushButton_clicked();
void on_listView_entered(const QModelIndex &index);
void on_listView_activated(const QModelIndex &index);
private:
Ui::MainWindow *ui;
QGraphicsView *mView;
QGraphicsScene *mScene;
QGraphicsTextItem *mText;
StringList *newString;
QStringListModel *model;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
mView = new QGraphicsView();
mScene = new QGraphicsScene();
ui->graphicsView->setScene(mScene);
QFont font;
font.setPixelSize(10);
font.setBold(false);
font.setFamily("Calibri");
mText = new QGraphicsTextItem;
mText->setPos(150,70);
mScene->addText(tr("Boat outside alarm area"))->setDefaultTextColor(Qt::black);
model = new QStringListModel();
ui->listView->setModel(model);
ui->listView->setEditTriggers(QAbstractItemView::NoEditTriggers);
emptyIndex();
connect(ui->listView, SIGNAL(loggingUpdated()), this, SLOT(updateListView(const QString &)));
connect(ui->graphicsView, SIGNAL(clicked(const QModelIndex &)), this, SLOT(on_listView_activated(const QModelIndex &index)));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::updateListView(const QString & message)
{
if(model->insertRow(model->rowCount())) {
QModelIndex index = model->index(model->rowCount() - 1, 0);
model->setData(index, message);
ui->listView->scrollTo(index);
}
}
void MainWindow::on_pushButton_clicked()
{
QString str = ui->lineEdit->text();
model->insertRow(model->rowCount());
QModelIndex index = model->index(model->rowCount()-1);
model->setData(index, str);
ui->listView->scrollToBottom();
}
void MainWindow::on_comboBox_currentIndexChanged(const QString &arg1)
{
QString list = ui->comboBox->currentText();
ui->lineEdit->setText(list);
Q_UNUSED(arg1)
}
void MainWindow::on_listView_activated(const QModelIndex &index)
{
QStringList allStrings = model->stringList();
QString last = allStrings.last();
if(last.startsWith("[ INFO] Minimum Distance: 5"))
{
ui->graphicsView->setBackgroundBrush(QColor(Qt::red));
}
else if(last.startsWith("[ INFO] Minimum Distance: 10"))
{
ui->graphicsView->setBackgroundBrush(QColor(Qt::yellow));
}
else if(last.startsWith("[ INFO] Minimum Distance: 15"))
{
ui->graphicsView->setBackgroundBrush(QColor(Qt::green));
}
Q_UNUSED(index)
}
EDIT 2
mainwindow.h
#include <QMainWindow>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsTextItem>
#include <QStringListModel>
#include "listview.h"
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
public slots:
void setGraphicViewColor(QColor c);
private:
Ui::MainWindow *ui;
QGraphicsView *mView;
QGraphicsScene *mScene;
QGraphicsTextItem *mText;
QStringListModel *model;
ListView *myListView;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
mView = new QGraphicsView();
mScene = new QGraphicsScene();
ui->graphicsView->setScene(mScene);
QFont font;
font.setPixelSize(10);
font.setBold(false);
font.setFamily("Calibri");
mText = new QGraphicsTextItem;
mText->setPos(150,70);
mScene->addText(tr("Boat outside alarm area"))->setDefaultTextColor(Qt::black);
model = new QStringListModel();
ui->listView->setModel(model);
ui->listView->setEditTriggers(QAbstractItemView::NoEditTriggers);
connect(ui->listView, SIGNAL(changeColor(QColor)), this, SLOT(setGraphicViewColor(QColor)));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::setGraphicViewColor(QColor c)
{
qDebug() << "Update your graphicsView backgroundBrush" << c;
ui->graphicsView->setBackgroundBrush(Qt::green);
}
listview.h
#ifndef LISTVIEW_H
#define LISTVIEW_H
#include <QListView>
#include <QStringListModel>
class ListView : public QListView
{
Q_OBJECT
public:
ListView(QWidget *parent = nullptr);
signals:
void changeColor(QColor c);
protected:
void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles = QVector<int>()) override;
};
#endif // LISTVIEW_H
listview.cpp
#include "listview.h"
ListView::ListView(QWidget *parent)
: QListView(parent)
{}
void ListView::dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles)
{
QListView::dataChanged(topLeft, bottomRight, roles);
/**
* Assuming that you have just one item changed
* So topLeft == bottomRight
*/
if (topLeft.row() == model()->rowCount()-1){
QString last = topLeft.data().toString();
if(last.startsWith("[ INFO] Minimum Distance: 5")) {
emit changeColor(Qt::red);
} else if(last.startsWith("[ INFO] Minimum Distance: 10")) {
emit changeColor(Qt::yellow);
} else if(last.startsWith("[ INFO] Minimum Distance: 15")) {
emit changeColor(Qt::green);
}
}
}
Below the error and a screenshot of the ui that does not detect the change event:
The output of the .ui:
What I have done so far:
I have been doinf a lot of research about this problem and came across this source which was useful but could not solve the problem, but in addition it seems to use a QModelIndex and I am not sure this is exactly what I need for this small project.
Also I read this source which was useful to establish and capture the specific and unique string but in terms of changing colors I could not solve that.
Thank you very much for pointing in the right direction for solving this issue.

Answer 1

If I well understand, you want to change the backgroundBrush of your graphicsView if the last item of your QStringListModel starts with your specific strings.
To detect this, you can subclass QListView:
listview.h:
#ifndef LISTVIEW_H
#define LISTVIEW_H
#include <QListView>
#include <QStringListModel>
class ListView : public QListView
{
Q_OBJECT
public:
ListView(QWidget *parent = nullptr);
signals:
void changeColor(QColor c);
protected:
void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles = QVector<int>()) override;
};
#endif // LISTVIEW_H
listview.cpp:
#include "listview.h"
ListView::ListView(QWidget *parent)
: QListView(parent)
{
}
void ListView::dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight, const QVector<int> &roles)
{
QListView::dataChanged(topLeft, bottomRight, roles);
/**
* Assuming that you have just one item changed
* So topLeft == bottomRight
*/
if (topLeft.row() == model()->rowCount()-1){
QString last = topLeft.data().toString();
if(last.startsWith("[ INFO] Minimum Distance: 5")) {
emit changeColor(Qt::red);
} else if(last.startsWith("[ INFO] Minimum Distance: 10")) {
emit changeColor(Qt::yellow);
} else if(last.startsWith("[ INFO] Minimum Distance: 15")) {
emit changeColor(Qt::green);
}
}
}
Now you have all what you need, but you need to add a slot to connect the signal of your custom ListView with your QGraphicsView::brush
// Add this in your mainwindows.h
public slots:
void setGraphicViewColor(QColor c);
// This in the ctor of your MainWindow:
connect(ui->listView, SIGNAL(changeColor(QColor)), this, SLOT(setGraphicViewColor(QColor)));
// And the implementation of your custom slot in mainwindows.cpp
void MainWindow::setGraphicViewColor(QColor c)
{
qDebug() << "Update your graphicsView backgroundBrush" << c;
//ui->graphicsView->setBackgroundBrush(c);
}