JTabbedPane track previous tab selection

Question

I have a class that extends BasicTabbedPaneUI and does some paint component overriding.

I want to be able to add a addMouseListener to the class I use it in to check when the user selects a tab the current tab index and the previous tab index.

NOTE: The user is able to navigate to tabs via the keyboard and not just clicking on a tab and I want to be able to make sure the previous index tracks this. So in the example below preIndex would equal the previous index regardless to whether the user navigated to it via the keyboard or mouse.

Any ideas please?

    tabbedPane.addMouseListener(new MouseAdapter() {
        @Override
        public void mousePressed(MouseEvent e) {
            JTabbedPane tabP = (JTabbedPane) e.getSource();
            int currIndex = tabP.indexAtLocation(e.getX(), e.getY());

            int prevIndex = ?????
        }
    });

Many thanks!!!!

score 3 · Accepted Answer · edited Aug 22 '17 at 19:09

I would use the change listener instead of mouse listener (it's called in both cases: for mouse and key event triggered tab change). If you cannot determine previously selected tab you can use following approach: save currently selected tab index as client property of the tabbed pane.

private static final String OLD_TAB_INDEX_PROPERTY = "oldTabIdx";

tabbedPane.addChangeListener(new ChangeListener() {
  public void stateChanged(ChangeEvent e) {
    JTabbedPane tabP = (JTabbedPane) e.getSource();
    int currIndex = tabP.getSelectedIndex();

    int oldIdx = 0;
    Object old = tabP.getClientProperty(OLD_TAB_INDEX_PROPERTY);
    if (old instanceof Integer) {
      oldIdx = (Integer) old;
    }
    tabP.putClientProperty(OLD_TAB_INDEX_PROPERTY, currIndex);
    // now we can use old and current index
  }
});

JTabbedPane track previous tab selection

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