push button is able to recieve output only once!!!

[Choti]

void MainWindow:n_pushButton_2_clicked()
{

QListWidgetItem *item = ui->valueWidget->currentItem();
item->setFlags(item->flags()|Qt :: ItemIsEditable);
ui->valueWidget->editItem(item);

}


this is my code which I have implemented for EDIT button. In valueWidget I have the values which I am going to edit. But when I click on EDIT button directly the window is crashing down.

[Lesiok]

Maybe ui->valueWidget->currentItem() returns NULL pointer. Use debugger to locate a problem.

[Choti]

Thank you Mr.Lesiok,


Do you think I can use another function instead of currentItem(); ??

[Lesiok]

No, I think you need to find the cause of the problem and not invent its workaround.

[Choti]

Yes ui->valuewidget->currentItem() ; is returning null pointer....

[anda_skoa]

Which means the cause of the problem is calling methods on a null pointer.

If you can find a way to check the value of the pointer you could change the code to only use the pointer if it is valid.

As a next step, it might be possible to get notified when the current item changes and apply the same check to determine a good value for the EDIT button's "enabled" property.

Cheers,
_

[Choti]

I could not find the solution

[anda_skoa]

The language feature you are looking for is called "if".
It allows to test a logical condition and then execute code depending on whether the expression evalutes to "true" or "false".

if (condition) {
    // code executed when the condition is true
} else {
    // code executed when the condition is false
}

if (condition) {
    // code executed when the condition is true
} else {
    // code executed when the condition is false
}

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The "else" case is optional.

In your case you can either check for the pointer being null and the code to execute being "return" or you can check for not being null and executing the code that uses the pointer.

Cheers,
_

P.S.: I would strongly recommend to work through a tutorial on C++ basics before continuing.