I have a simple interface that is designed to select one or more seats in a theater and reserve them for yourself.
I have three columns: zone / row / seat. You select the first to populate the second, and the second to populate the third.
When I select them the first time no problem.
If I change the second row, the third row re-populates (in this case all rows have the same number of seats) it does not break!
However if I change the first row everything breaks!
Now the reason for this is kinda clear, but I don't understand exactly why this is.
This is the first list event trigger:
List_Zona.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent arg0) {
if (! arg0.getValueIsAdjusting()){
RowListModel.clear(); // second list
SeatListModel.clear(); // third list
List_Rand.clearSelection(); // second list
List_Scaun.clearSelection(); // third list
int[] rows = self.repository.getRowsForZone(
List_Zona.getSelectedValue().toString()
);
int index = 0;
while (rows[index]!=0) {
RowListModel.addElement(String.valueOf(rows[index]));
index++;
}
}
}
});
It should clear the other column selections so it should not interfere with this next trigger (second column), but apparently it does, or something happens which I don't get:
List_Rand.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent arg0) {
if (! arg0.getValueIsAdjusting()){
SeatListModel.clear();
int[] seats = self.repository.getSeatByZoneAndRow(
List_Zona.getSelectedValue().toString(),
Integer.parseInt(List_Rand.getSelectedValue().toString())//HERE
);
int index = 0;
while (seats[index]!=0) {
SeatListModel.addElement(String.valueOf(seats[index]));
index++;
}
}
}
});
It can't parse the integer because the second column should be cleared, but it's not ? But even though it's not ... it is ?
What I'm trying to say: The second column should be clear (it's not) but if it's not then the error should not occur, but it does.
I hope this makes some sense!
Can anyone spot the problem ? Should I provide more code ?
The error is a NullPointerException at the second column, because something fishy is happening there (again: at the integer parsing).
By my mind the second column's valueChanged
should not trigger at all when I click an item in the first column. It should just clear the other two and that's that. Why am I wrong ?
P.S. First Code snippet is responsible for the second one breaking the program.
Maybe I should also rephrase the question How can I safely clear everything when I re-select a new "Zone" (Zona) - Column one ?