TableView: adjust number of visible rows

Question

I\'m using this table to display data in Table View:

import javafx.application.Application;
import javafx.beans.property.IntegerProperty;
import javafx.beans         


        

Answer 1

Unfortunately, configuration of the visibleRowCount isn't supported in TableView (you might consider filing a feature request in fx' jira - no need, already done years ago). And it's not entirely straightforward to let the view return a prefHeight based on a such a preference: we'll need to measure the size requirements of the "real" cell and that's somehow buried inside the bowels.

Just for fun, experimented with extending the whole stack of collaborators:

• a custom tableView that has a visibleRowCount property
• a custom skin that listens to the property calculates its prefHeight depending on it
• some way to access the height of the "real" cell - the only class with all info to measure it, is the VirtualFlow. As the relevant method is protected, this requires either a custom VirtualFlow that exposes that method or reflective access.

The code:

/**
 * TableView with visibleRowCountProperty.
 * 
 * @author Jeanette Winzenburg, Berlin
 */
public class TableViewWithVisibleRowCount extends TableView {

    private IntegerProperty visibleRowCount = new SimpleIntegerProperty(this, "visibleRowCount", 10);
    
    
    public IntegerProperty visibleRowCountProperty() {
        return visibleRowCount;
    }
    
    @Override
    protected Skin createDefaultSkin() {
        return new TableViewSkinX(this);
    }
    
    /**
     * Skin that respects table's visibleRowCount property.
     */
    public static class TableViewSkinX extends TableViewSkin {

        public TableViewSkinX(TableViewWithVisibleRowCount tableView) {
            super(tableView);
            registerChangeListener(tableView.visibleRowCountProperty(), "VISIBLE_ROW_COUNT");
            handleControlPropertyChanged("VISIBLE_ROW_COUNT");
        }
        
        @Override
        protected void handleControlPropertyChanged(String p) {
            super.handleControlPropertyChanged(p);
            if ("VISIBLE_ROW_COUNT".equals(p)) {
                needCellsReconfigured = true;
                getSkinnable().requestFocus();
            }
        }

        /**
         * Returns the visibleRowCount value of the table.
         */
        private int getVisibleRowCount() {
            return ((TableViewWithVisibleRowCount) getSkinnable()).visibleRowCountProperty().get();
        }
        
        /**
         * Calculates and returns the pref height of the 
         * for the given number of rows.
         * 
         * If flow is of type MyFlow, queries the flow directly
         * otherwise invokes the method.
         */
        protected double getFlowPrefHeight(int rows) {
            double height = 0;
            if (flow instanceof MyFlow) {
                height = ((MyFlow) flow).getPrefLength(rows);
            }
            else {
                for (int i = 0; i < rows && i < getItemCount(); i++) {
                    height += invokeFlowCellLength(i);
                }
            }    
            return height + snappedTopInset() + snappedBottomInset();

        }
        
        /**
         * Overridden to compute the sum of the flow height and header prefHeight.
         */
        @Override
        protected double computePrefHeight(double width, double topInset,
                double rightInset, double bottomInset, double leftInset) {
            // super hard-codes to 400 .. doooh
            double prefHeight = getFlowPrefHeight(getVisibleRowCount());
            return prefHeight + getTableHeaderRow().prefHeight(width);
        }
        
        /**
         * Reflectively invokes protected getCellLength(i) of flow.
         * @param index the index of the cell.
         * @return the cell height of the cell at index.
         */
        protected double invokeFlowCellLength(int index) {
            double height = 1.0;
            Class clazz = VirtualFlow.class;
            try {
                Method method = clazz.getDeclaredMethod("getCellLength", Integer.TYPE);
                method.setAccessible(true);
                return ((double) method.invoke(flow, index));
            } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
                e.printStackTrace();
            }
            return height;
        }

        /**
         * Overridden to return custom flow.
         */
        @Override
        protected VirtualFlow createVirtualFlow() {
            return new MyFlow();
        }
        
        /**
         * Extended to expose length calculation per a given # of rows.
         */
        public static class MyFlow extends VirtualFlow {

            protected double getPrefLength(int rowsPerPage) {
                double sum = 0.0;
                int rows = rowsPerPage; //Math.min(rowsPerPage, getCellCount());
                for (int i = 0; i < rows; i++) {
                    sum += getCellLength(i);
                }
                return sum;
            }

        }
        
    }

    @SuppressWarnings("unused")
    private static final Logger LOG = Logger.getLogger(TableViewWithVisibleRowCount.class
            .getName());
}

Note that you might get away with a plain override of table's prefHeight when having a fixed-cell-size, didn't try that - no risk no fun :-)

---

Update: the custom skin in javafx15 - basically the same, just some access details changed (in both directions ;)

/**
 * Skin that respects table's visibleRowCount property.
 */
public class TableViewSkinX extends TableViewSkin {

    public TableViewSkinX(TableViewWithVisibleRowCount tableView) {
        super(tableView);
        registerChangeListener(tableView.visibleRowCountProperty(), e -> visibleRowCountChanged());
    }
    
    private void visibleRowCountChanged() {
        getSkinnable().requestLayout();
    }
    
    /**
     * Returns the visibleRowCount value of the table.
     */
    private int getVisibleRowCount() {
        return ((TableViewWithVisibleRowCount) getSkinnable()).visibleRowCountProperty().get();
    }
    
    /**
     * Calculates and returns the pref height of the for the given number of
     * rows.
     */
    protected double getFlowPrefHeight(int rows) {
        double height = 0;
        for (int i = 0; i < rows && i < getItemCount(); i++) {
            height += invokeFlowCellLength(i);
        }
        return height + snappedTopInset() + snappedBottomInset();
    }
    
    /**
     * Overridden to compute the sum of the flow height and header prefHeight.
     */
    @Override
    protected double computePrefHeight(double width, double topInset,
            double rightInset, double bottomInset, double leftInset) {
        // super hard-codes to 400 .. doooh
        double prefHeight = getFlowPrefHeight(getVisibleRowCount());
        return prefHeight + getTableHeaderRow().prefHeight(width);
    }
    
    /**
     * Reflectively invokes protected getCellLength(i) of flow.
     * @param index the index of the cell.
     * @return the cell height of the cell at index.
     */
    protected double invokeFlowCellLength(int index) {
        // note: use your own utility method to reflectively access internal fields/methods
        return (double) FXUtils.invokeGetMethodValue(VirtualFlow.class, getVirtualFlow(), 
                "getCellLength", Integer.TYPE, index);
    }

}