How to know if a JScrollBar has reached the bottom of the JScrollPane?

java, jscrollbar, jscrollpane, swing

Solution

You have to add the extent of the scrollbar to your calculation. I added the code into your code in the example below.

scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {
    @Override
    public void adjustmentValueChanged(AdjustmentEvent ae) {
        int extent = scrollPane.getVerticalScrollBar().getModel().getExtent();
        System.out.println("Value: " + (scrollPane.getVerticalScrollBar().getValue()+extent) + " Max: " + scrollPane.getVerticalScrollBar().getMaximum());
    }
});

Two alternative implementations (partially reacting to Kleopatra)

scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {

    @Override
    public void adjustmentValueChanged(AdjustmentEvent event) {
        JScrollBar scrollBar = (JScrollBar) event.getAdjustable();
        int extent = scrollBar.getModel().getExtent();
        System.out.println("1. Value: " + (scrollBar.getValue() + extent) + " Max: " + scrollBar.getMaximum());

    }
});

Or via the model

scrollPane.getVerticalScrollBar().getModel().addChangeListener(new ChangeListener() {

    @Override
    public void stateChanged(ChangeEvent event) {
        BoundedRangeModel model = (BoundedRangeModel) event.getSource();
        int extent = model.getExtent();
        int maximum = model.getMaximum();
        int value = model.getValue();

        System.out.println("2. Value: " + (value + extent) + " Max: " + maximum);

    }
});

Problem

I'd like to know if there is a way to know when a `JScrollBar` (vertical in my case) has reached the bottom of his containing `JScrollPane`. At first i have though of using an `AdjustmentListener` on the scroll bar but i don't know how to interpret the `value` attribute of the `JScrollBar`. Also i'm not sure to properly understand what the `maximum` represents and if i can use with the value to get the information i need. Edit: ``` scrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() { @Override public void adjustmentValueChanged(AdjustmentEvent ae) { System.out.println("Value: " + scrollPane.getVerticalScrollBar().getValue() + " Max: " + scrollPane.getVerticalScrollBar().getMaximum()); } } ```

Original source