How can I get the component at the mouse click pos

Question

I use a custom TableCellRenderer with multiple JFormattedTextField in the table cells. I use the same component as TableCellEditor. Now I need to know in what JFormattedTextField the user clicked, and also where in this field (can be done with viewToModel).

When using a custom TableCellEditor, the only way to get the Point from the mouse click is the isCellEditable(EventObject e) method in CellEditor. The Point given is in the parents coordinate system.

anEvent is in the invoking component coordinate system.

But how can I get the component at the clicked coordinate? I have tried with findComponentAt(Point p) but it returns null for me.

Here is some code I have tested with:

@Override
    public boolean isCellEditable(EventObject e) {

        if(e instanceof MouseEvent) {
            MouseEvent ev = (MouseEvent)e;
            Point p = ev.getPoint();

            // gives strange values
            Point p3 = editor.getLocation();

            // x: 0 y: 0
            Point tp = ((JTable)e.getSource()).getLocation();

            // these returns null
            Component c1 = renderer.findComponentAt(p);
            Component c2 = editor.findComponentAt(p);

            System.out.println("Click at " + p + " editor at: " + p3);
        }

        return true;
    }

The values for the component's location editor.getLocation(); gives almost random values for the y-coordinate (e.g. when using 5 rows in the table).

How can I get the component the user clicked on when using a TableCellEditor and a TableCellRenderer?

---

Here is a full example:

public class FormattedTableEditDemo extends JFrame {

    public FormattedTableEditDemo() {

        MyTableModel model = new MyTableModel();
        MyTableCellEditorAndRenderer cellEditorAndRenderer =
                new MyTableCellEditorAndRenderer();     

        JTable table = new JTable(model);
        table.setDefaultRenderer(BigDecimal.class, cellEditorAndRenderer);
        table.setDefaultEditor(BigDecimal.class, cellEditorAndRenderer);
        table.setRowHeight(40);

        add(new JScrollPane(table));
        pack();
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);

    }

    class MyTableCellEditorAndRenderer extends AbstractCellEditor
            implements TableCellEditor, TableCellRenderer {

        MyCellPanel editor = new MyCellPanel();
        MyCellPanel renderer = new MyCellPanel();

        @Override
        public Object getCellEditorValue() {
            return editor.getValue();
        }

        @Override
        public Component getTableCellRendererComponent(JTable table, 
                Object value, boolean isSelected, boolean hasFocus,
                int row, int column) {
            renderer.setValue(value);
            return renderer;
        }

        @Override
        public Component getTableCellEditorComponent(JTable table,
                Object value, boolean isSelected, int row, int column) {
            editor.setValue(value);
            return editor;
        }

        @Override
        public boolean shouldSelectCell(EventObject e) {
            return false;
        }

        @Override
        public boolean isCellEditable(EventObject e) {

            if(e instanceof MouseEvent) {
                MouseEvent ev = (MouseEvent)e;
                Point p = ev.getPoint();

                // gives strange values
                Point p3 = editor.getLocation();

                // x: 0 y: 0
                Point tp = ((JTable)e.getSource()).getLocation();

                // these returns null
                Component c1 = renderer.findComponentAt(p);
                Component c2 = editor.findComponentAt(p);

                System.out.println("Click at " + p + " editor at: " + p3);
            }

            return true;
        }

    }

    class MyCellPanel extends JPanel {

        JFormattedTextField field1 = new JFormattedTextField();
        JFormattedTextField field2 = new JFormattedTextField();

        public MyCellPanel() {

            field1.setColumns(8);
            field2.setColumns(8);

            field2.setValue(new BigDecimal("0.00"));

            setLayout(new BorderLayout());
            add(field1, BorderLayout.WEST);
            add(Box.createHorizontalStrut(30));
            add(field2, BorderLayout.EAST);
        }

        public Object getValue() {
            return field1.getValue();
        }

        public void setValue(Object value) {
            field1.setValue(value);
        }
    }

    class MyTableModel extends AbstractTableModel {

        List<BigDecimal> values = new ArrayList<BigDecimal>();

        public MyTableModel() {

            // test values
            values.add(new BigDecimal("37.00"));
            values.add(new BigDecimal("4305.90"));
            values.add(new BigDecimal("386.04"));
            values.add(new BigDecimal("3486.58"));
            values.add(new BigDecimal("6546.45"));
        }

        @Override
        public int getColumnCount() {
            return 1;
        }

        @Override
        public int getRowCount() {
            return values.size();
        }

        @Override
        public Object getValueAt(int row, int column) {
            return values.get(row);
        }

        @Override
        public boolean isCellEditable(int row, int column) {
            return true;
        }

        @Override
        public Class<?> getColumnClass(int column) {
            return BigDecimal.class;
        }

    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new FormattedTableEditDemo();
            }

        });
    }

}

Answer 1

You can get the table's row and column from the clicked point. Then call the same renderer's getTableCellRendererComponent method to get renderer component. Then correct point subtracting previous rows' heights from y and previous cells' widths from x. Then get proper child of rendered component.

Answer 2

Not entirely sure I understand what's going wrong (just let me know if I'm off, so I can delete this :-)

Assuming you want to get the "real" component under the mouse (click/press) which triggered the start of editing, the trick is to do the conversion (from parent to editor coordinates) after the editor is added to its parent. That's guaranteed for shouldSelectCell, but not for isCellEditable (the latter being called before)

A recent answer in the context of a tree (should be similar enough) has some runnable example. Here's the relevant snippet:

/**
 * At this point in time the editing component is added to the table (not documented!) but
 * table's internal cleanup might not yet be ready
 */ 
@Override
public boolean shouldSelectCell(EventObject anEvent) {
    if (anEvent instanceof MouseEvent) {
        redirect((MouseEvent) anEvent);
    }
    return false;
}

private void redirect(final MouseEvent anEvent) {
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            MouseEvent ev = SwingUtilities.convertMouseEvent(anEvent.getComponent(), anEvent, editor);
            // at this point you have the mouse coordinates in the editor's system
            // do stuff, like f.i. findComponent
            ....
        }
    });
}

Answer 3

This is not an answer to your question but an explanation of the result you see: findComponentAt() returns null because "there is no child component at the requested point." MyCellPanel is located on a CellRendererPane used by JTable to speed rendering. There's an example of how it's used here.