Pretty simple task but I didn't manage to find anything useful in documentation. I want a QTreeView to contain a single column called "Files" with data from QFileSystemView. Here's what I've got:
QFileSystemModel *projectFiles = new QFileSystemModel();
projectFiles->setRootPath(QDir::currentPath());
ui->filesTree->setModel(projectFiles);
ui->filesTree->setRootIndex(projectFiles->index(QDir::currentPath()));
// hide all but first column
for (int i = 3; i > 0; --i)
{
ui->filesTree->hideColumn(i);
}
That gives me a single column with "Name" header. How do I rename this header?
QAbstractItemModel::setHeaderData() should work. If not, you can always inherit from QFileSystemModel and override headerData().
Quick but a little dirty trick (please note w.hideColumn()):
#include <QApplication>
#include <QFileSystemModel>
#include <QTreeView>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QTreeView w;
QFileSystemModel m;
m.setFilter(QDir::Dirs | QDir::NoDotAndDotDot);
m.setRootPath("C:\\");
w.setModel(&m);
w.setRootIndex(m.index(m.rootPath()));
w.hideColumn(3);
w.hideColumn(2);
w.hideColumn(1);
w.show();
return a.exec();
}
You can subclass QFileSystemModel and overide method headerData(). For example, if you want only to change first header label and leave the rest with their original values, you can do:
QVariant MyFileSystemModel::headerData(int section, Qt::Orientation orientation, int role) const {
if ((section == 0) && (role == Qt::DisplayRole)) {
return "Folder";
} else {
return QFileSystemModel::headerData(section,orientation,role);
}
}
Related
is it possible to restrict the length in a QInputDialog::getText? For example, I want to restrict the length from the user input to 10 characters directly in the InputDialog. Unfortunately, there isn't a function like QInputDialog::setMaximum.
Here's my current code:
QString input = QInputDialog::getText(this, tr("Find"), tr("Enter text:"), QLineEdit::Normal, "", nullptr, Qt::WindowFlags(), Qt::ImhDialableCharactersOnly);
if (input == "")
return;
else if (input.length() > 10)
{
QMessageBox::warning(this, tr("Invalid input", "Note #1"), tr("Input is too long."));
// This is this function name (calls itself again)
on_actionFind_triggered();
}
...
Very easy with a signal/slot mechanism and a signal blocker...
#include <QApplication>
#include <QInputDialog>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QInputDialog w;
QObject::connect(&w, &QInputDialog::textValueChanged,
[&w](QString text){ if (text.length() > 10) { QSignalBlocker s(w); w.setTextValue(text.left(10)); } });
w.show();
return a.exec();
}
Another posibility would be to find QLineEdit child of the dialog using and then assign a certain QValidator to it. I have not tested this but it should work as well. But then you would need to program the maximum length validator.
auto lineEdit = inputDialog->findChild<QLineEdit*>();
lineEdit->setValidator(validator);
I'm trying to generate a simple QTreeView inside another widget (QMainWindow). The following code works as expected and displays the tree-view,
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
MainWindow w;
w.show();
QString rootPath = "C:/";
QFileSystemModel model;
model.setRootPath("");
QTreeView tree;
tree.setModel(&model);
if (!rootPath.isEmpty()) {
const QModelIndex rootIndex = model.index(QDir::cleanPath(rootPath));
if (rootIndex.isValid())
tree.setRootIndex(rootIndex);
}
tree.setParent(&w);
tree.show();
return app.exec();
}
but if I extract the code that generates the tree-view, nothing seems to happen. The extracted function is as follows:
void create_tree(QMainWindow *w) {
QString rootPath = "C:/";
QFileSystemModel model;
model.setRootPath("");
QTreeView tree;
tree.setModel(&model);
if (!rootPath.isEmpty()) {
const QModelIndex rootIndex = model.index(QDir::cleanPath(rootPath));
if (rootIndex.isValid())
tree.setRootIndex(rootIndex);
}
tree.setParent(w);
tree.show();
}
and the corresponding function call in main function is as follows:
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
MainWindow w;
w.show();
create_tree(&w);
return app.exec();
}
How does the extracted function create_tree work and why is it not showing the tree view?
QFileSystemModel model;
and
QTreeView tree;
Are local stack variables, meaning they will be gone once you exit the create_tree function.
You can solve your issue by creating them on the heap by using new, which will keep them alive. Be careful, that you need to think about how you destroy these created objects. The Qt parenting system is a great help there, because the parent will destroy its children when it is destroyed, so your tree view is fine. You should think about good parent for your model to make sure you create no memory leak.
A working version of your function looks like this - be careful that you still need to handle the models deletion:
void create_tree(QMainWindow *w) {
QString rootPath = "C:/";
QFileSystemModel* model = new QFileSystemModel();
model->setRootPath("");
QTreeView* tree = new QTreeView();
tree->setModel(model);
if (!rootPath.isEmpty()) {
const QModelIndex rootIndex = model->index(QDir::cleanPath(rootPath));
if (rootIndex.isValid())
tree->setRootIndex(rootIndex);
}
tree->setParent(w);
tree->show();
}
I am trying to connect row selections from two QTableWidget.
I mean, when I select one row in Table 1, I want my program selects the same row in table 2. The two table dont have the same number of column so I cannot just select one item for the first and select the same item on the second able.
I have tried to use the following without success:
connect(ui->table1->selectionModel(), SIGNAL(currentRowChanged(QModelIndex, QModelIndex)), ui->table2->selectionModel(), SLOT(setCurrentIndex(QModelIndex)));
It is written:
QObject::connect: No such slot QItemSelectionModel::setCurrentIndex(QModelIndex)
Do you know what is going wrong?
The problem is caused because setCurrentIndex() has two parameters, and not just one, plus the signatures do not match. So in these cases you should use a lambda and use selectRow():
#include <QApplication>
#include <QHBoxLayout>
#include <QTableWidget>
#include <QItemSelectionModel>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
auto *table1 = new QTableWidget(4, 3);
table1->setSelectionBehavior(QAbstractItemView::SelectRows);
auto table2 = new QTableWidget(4, 4);
table2->setSelectionBehavior(QAbstractItemView::SelectRows);
QObject::connect(table1->selectionModel(), &QItemSelectionModel::currentRowChanged,
[table2](const QModelIndex ¤t, const QModelIndex & previous)
{
if(previous.isValid())
table2->selectRow(current.row());
});
QWidget w;
auto lay = new QHBoxLayout(&w);
lay->addWidget(table1);
lay->addWidget(table2);
w.show();
return a.exec();
}
I am trying to create pop-up menu depending on a variable as follows:
QMenu menu(widget);
for(int i = 1; i <= kmean.getK(); i++)
{
stringstream ss;
ss << i;
string str = ss.str();
string i_str = "Merge with " + str;
QString i_Qstr = QString::fromStdString(i_str);
menu.addAction(i_Qstr, this, SLOT(mergeWith1()));
}
menu.exec(position);
where:
kmean.get(K) returns an int value,
mergeWith1() is some `SLOT()` which works fine
Issue:
The loop creates an action on menu only for i=1 case, and ignores other values of i.
Additional information
When doing the same loop with casual int values (without convert) everything works fine. e.g. if I do in loop only menu.addAction(i, this, SLOT(...))) and my K=4, a menu will be created with four actions in it, named 1, 2, 3, 4 correspondingly.
What can be the problem caused by
I think the issue is in convert part, when I convert i to string using stringstream and after to QString. May be the value is somehow lost. I am not sure.
QESTION:
How to make the loop accept the convert part?
What do I do wrong in convert part?
In Qt code, you shouldn't be using std::stringstream or std::string. It's pointless.
You have a crashing bug by having the menu on the stack and giving it a parent. It'll be double-destructed.
Don't use the synchronous blocking methods like exec(). Show the menu asynchronously using popup().
In order to react to the actions, connect a slot to the menu's triggered(QAction*) signal. That way you can deal with arbitrary number of automatically generated actions.
You can use the Qt property system to mark actions with custom attributes. QAction is a QObject after all, with all the benefits. For example, you can store your index in an "index" property. It's a dynamic property, created on the fly.
Here's a complete example of how to do it.
main.cpp
#include <QApplication>
#include <QAction>
#include <QMenu>
#include <QDebug>
#include <QPushButton>
struct KMean {
int getK() const { return 3; }
};
class Widget : public QPushButton
{
Q_OBJECT
KMean kmean;
Q_SLOT void triggered(QAction* an) {
const QVariant index(an->property("index"));
if (!index.isValid()) return;
const int i = index.toInt();
setText(QString("Clicked %1").arg(i));
}
Q_SLOT void on_clicked() {
QMenu * menu = new QMenu();
int last = kmean.getK();
for(int i = 1; i <= last; i++)
{
QAction * action = new QAction(QString("Merge with %1").arg(i), menu);
action->setProperty("index", i);
menu->addAction(action);
}
connect(menu, SIGNAL(triggered(QAction*)), SLOT(triggered(QAction*)));
menu->popup(mapToGlobal(rect().bottomRight()));
}
public:
Widget(QWidget *parent = 0) : QPushButton("Show Menu ...", parent) {
connect(this, SIGNAL(clicked()), SLOT(on_clicked()));
}
};
int main (int argc, char **argv)
{
QApplication app(argc, argv);
Widget w;
w.show();
return app.exec();
}
#include "main.moc"
I was reading MVC tutorial and wanted to try out the code, but for some reason (which I'm not able to figure out) it is not working.
This code is suppose to show contents of current directory in QListWidget.
#include <QApplication>
#include <QFileSystemModel>
#include <QModelIndex>
#include <QListWidget>
#include <QListView>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QFileSystemModel *model = new QFileSystemModel;
QString dir = QDir::currentPath();
model->setRootPath(dir);
QModelIndex parentIndex = model->index(dir);
int numRows = model->rowCount(parentIndex);
QListWidget *list = new QListWidget;
QListWidgetItem *newItem = new QListWidgetItem;
for(int row = 0; row < numRows; ++row) {
QModelIndex index = model->index(row, 0, parentIndex);
QString text = model->data(index, Qt::DisplayRole).toString();
newItem->setText(text);
list->insertItem(row, newItem);
}
list->show();
return a.exec();
}
There are 2 problems.
The first described by Frank Osterfeld's answer. Move:
QListWidgetItem *newItem = new QListWidgetItem;
into your loop.
The second has to do with QFileSystemModel's threading model. from the docs for QFileSystemModel:
Unlike the QDirModel, QFileSystemModel uses a separate thread to populate itself so it will not cause the main thread to hang as the file system is being queried. Calls to rowCount() will return 0 until the model populates a directory.
and
Note: QFileSystemModel requires an instance of a GUI application.
I don't think QFileSystemModel() will work properly until after the Qt event loop is running (which is started by a.exec() in your example).
In your case, model->rowCount(parentIndex) returns 0, even though there are items in the directory (at least that's what it's doing on my test).
Replacing QFileSystemModel with QDirModel (and removing the model->setRootPath(dir) call, which QDirModel` doesn't support) populates the list.
You must create a new item for each row. Move
QListWidgetItem *newItem = new QListWidgetItem;
into the for loop.