The connect statement is incorrect: you don't put signal/slot parameter name in the connect statement (so just const QString& remove currentText) and a second stuff is that most likely you would like the changeWidget() to take that string that changed in the QLisWidget and create/modify the widget accordingly with that QString: so you can create void changeWidget(const QString& changedText) (if you didn't put it now, don't forget to add public slots: access specifier) and use the text (changed from the QListWidget) into definition to create/update the widget so the connect will become:
Qt Code: 
  1. connect(ui->listWidget_settings, SIGNAL(currentTextChanged ( const QString& )),this, SLOT(changeWidget(const QString&))); //at connect you write just the type of parameters
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