Regarding Signals and Slots

Shruthi

This post is deleted!

mrjj

Hi
if the goal is to block signals then as jonB says you must do

ui->tableWidget->blockSignals(true);
xxxxx
ui->tableWidget->blockSignals(false);

not reverse

JonB

@Shruthi
As @mrjj has just said. All you were supposed to do was swap one false with one true.

Shruthi

@JonB @mrjj Ya I tried swapping, but it's still the same.

Shruthi

Can we achieve this without using blocksignals? If so, what changes needs to be done? @JonB @mrjj

JonB

@Shruthi
So your slot is firing while you are initialising. You have a couple of choices:

Here you also want to block signals during fillTableWidget(), so add that; or
Do not connect() the slot till after fillTableWidget() has done its work. If you are using Designer's autoconnect of slots change over to your own connects.

Christian Ehrlicher

Just one question - what should fillTableWidget() do at all (apart from the fact that it does not compile at all)? When rowCount() is greater than 0 then empty QTableWidgetItem's are set, nothing more.

Please provide a minimal, compilable example to reproduce your issue!

Shruthi

This post is deleted!

Christian Ehrlicher

Again: your code does not even compile so how did you check it? What should your function do at all? And on_tableWidget_singleitemchanged() also crashes when there is at least one row.

Provide a fully, minimal compilable example!

Shruthi

@Christian-Ehrlicher It will compile and it fills the tablewidget with values. But the signal is not triggering correctly when user typed some value to the tablewidget.
Please check only the signal and slot and let me know, if I have missed anything in that.
Thank you.

Christian Ehrlicher

@Shruthi said in Regarding Signals and Slots:

s1 =->setTextAlignment(Qt::AlignCenter);

No, this does not compile!

it fills the tablewidget with values

No, it does not - you don't set a text to any of those QTableWidgetItems... provide compilable code!

JonB

@Shruthi said in Regarding Signals and Slots:

void gen_window::on_tableWidget_singleitemchanged( )

You have made the slot a member of gen_window.

connect(ui->tableWidget,SIGNAL(itemChanged()),this,SLOT(on_tableWidget_singleitemchanged()));

You connect to it as a member of this, which is MainWindow.

Why do that I don't know. But if you used new signal & slot connection syntax, as I say to everyone, you would have known immediately. If you must use old style, check return result from connect()s and allow for runtime errors.

mrjj

Hi
there is something wrong with slot and connect
its
void QTableWidget::itemChanged(QTableWidgetItem *item)

so connect is wrong as the parameter is not included
connect(ui->tableWidget,SIGNAL(itemChanged(QTableWidgetItem *)),this,SLOT(on_tableWidget_singleitemchanged(QTableWidgetItem *)));
(using the new syntax is far better )

and your slot is also not on the spot

void gen_window::on_tableWidget_singleitemchanged( )
{
QTableWidgetItem *item; <<< this is bad as danglining pointer. item should be the parameter

so its
void gen_window::on_tableWidget_singleitemchanged(QTableWidgetItem *item )
{
~~QTableWidgetItem *item;~~

Shruthi

@mrjj @JonB @Christian-Ehrlicher @JoeCFD Thank you all for the replies.