Jface: How to force Listviewer to resize

Question

how can I force a Listviewer to update the size? When I'm adding an element to the list which is longer then the existing size, the listviewer should expand:

I update the Listviewer in this way:

lvConstraints.refresh();

Answer 1

Are you sure it is a good idea, to resize it after content is added? IMO, expanding and collapsing at runtime, causes pretty bad user experience. Can't you think of an average width of elements, containing inside the viewer? For Longer elements I'd suggest you use scrolling functionality.

If you still want to change size of a viwer after element is added you can do it like this:

viewer.getControl().computeSize(SWT.DEFAULT, SWT.DEFAULT);
viewer.getControl().pack();

Example:

public class Test {

    private class MyContentProvider implements IStructuredContentProvider {

        @Override
        public Object[] getElements(Object inputElement) {
            return ((List) inputElement).toArray(new MyModel[0]);
        }

        @Override
        public void dispose() {
        }

        @Override
        public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
        }

    }

    public class MyModel {
        public String counter;

        public MyModel(String counter) {
            this.counter = counter;
        }

        @Override
        public String toString() {
            return "Item " + counter;
        }
    }

    public Test(Shell shell) {
        // final TableViewer v = new TableViewer(shell);
        Composite c = new Composite(shell, SWT.NONE);
        GridLayoutFactory.swtDefaults().applyTo(c);
        GridDataFactory.defaultsFor(c).hint(100, 100).applyTo(c);

        final ListViewer v = new ListViewer(c);
        // v.setSize(200, 300);
        v.setLabelProvider(new LabelProvider());
        // for demonstration purposes use custom content provider
        // alternatively you could use ArrayContentProvider.getInstance()
        v.setContentProvider(new MyContentProvider());
        v.setComparator(new ViewerComparator());
        v.setInput(createModel());

        GridDataFactory.defaultsFor(v.getControl()).align(SWT.BEGINNING, SWT.TOP).hint(100, 100).grab(true, true)
            .applyTo(v.getControl());
        // v.getTable().setLinesVisible(true);

        Button b = new Button(c, SWT.NONE);
        b.setText("button");
        b.addSelectionListener(new SelectionAdapter() {
            @Override
            public void widgetSelected(SelectionEvent e) {
                int nextInt = RandomUtils.nextInt(100);
                String s = "";
                for (int i = 0; i < nextInt; i++) {
                    s += "" + i;
                }
                // v.add(new MyModel(s));
                ((List) v.getInput()).add(new MyModel(s));
                v.refresh();
                v.getControl().computeSize(SWT.DEFAULT, SWT.DEFAULT);
                v.getControl().pack();
            }
        });
    }

    private List<MyModel> createModel() {
        List<MyModel> elements = new ArrayList<Test.MyModel>();

        for (int i = 0; i < 10; i++) {
            elements.add(new MyModel("" + i));
        }

        return elements;
    }

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        new Test(shell);
        shell.open();

        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }

        display.dispose();

    }

}

To show a vertical scrollbar, create viewer with SWT.V_SCROLL style: like this:

final ListViewer v = new ListViewer(c, SWT.V_SCROLL);

To prevent resizing more, then specific height, use height hint, when computing size and do it as follows (note, that you can provide width hint as well, to prevent resizing more, then specific width) (NOTE:: pack() method was removed):

v.refresh();
Point computeSize = v.getControl().computeSize(SWT.DEFAULT, 200);
v.getList().setSize(computeSize);