Fixes the page up/down keys and home/end keys to work on another JComponent from the one with the keyboard focus. - Java Swing

Java examples for Swing:JComponent

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Description

Fixes the page up/down keys and home/end keys to work on another JComponent from the one with the keyboard focus.

Demo Code


import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;
import javax.swing.*;

public class Main{
    /**//w  w w  .  ja va  2  s.  c o m
     * Fixes the page up/down keys and home/end keys to work on another component from the one with the keyboard focus.
     * This lets you offer convenient keyboard navigation like in Apple's Mail, where the arrow keys move through the inbox while the page keys move through the selected message.
     * Note that the home/end keys aren't redirected for text fields, on the assumption that they're needed for cursor movement.
     */
    public static void divertPageScrollingFromTo(
            final JComponent focusedComponent,
            final JComponent componentToPageScroll) {
        initKeyBinding(focusedComponent, KeyStroke.getKeyStroke("PAGE_UP"),
                new AbstractAction("pagePatchUp") {
                    public void actionPerformed(ActionEvent e) {
                        ComponentUtilities.scroll(componentToPageScroll,
                                true, -1);
                    }
                });
        initKeyBinding(focusedComponent,
                KeyStroke.getKeyStroke("PAGE_DOWN"), new AbstractAction(
                        "pagePatchDown") {
                    public void actionPerformed(ActionEvent e) {
                        ComponentUtilities.scroll(componentToPageScroll,
                                true, 1);
                    }
                });
        if (focusedComponent instanceof JTextField == false) {
            initKeyBinding(focusedComponent,
                    KeyStroke.getKeyStroke("HOME"), new AbstractAction(
                            "pagePatchToTop") {
                        public void actionPerformed(ActionEvent e) {
                            ComponentUtilities.scrollToExtremity(
                                    componentToPageScroll, true);
                        }
                    });
            initKeyBinding(focusedComponent, KeyStroke.getKeyStroke("END"),
                    new AbstractAction("pagePatchToBottom") {
                        public void actionPerformed(ActionEvent e) {
                            ComponentUtilities.scrollToExtremity(
                                    componentToPageScroll, false);
                        }
                    });
        }
    }
    /**
     * Binds an Action to a JComponent via the Action's configured ACCELERATOR_KEY.
     */
    public static void initKeyBinding(JComponent component, Action action) {
        KeyStroke keyStroke = (KeyStroke) action
                .getValue(Action.ACCELERATOR_KEY);
        initKeyBinding(component, keyStroke, action);
    }
    /**
     * Binds an Action to a JComponent via the given KeyStroke.
     */
    public static void initKeyBinding(JComponent component,
            KeyStroke keyStroke, Action action) {
        String name = (String) action.getValue(Action.NAME);
        component.getActionMap().put(name, action);
        component.getInputMap().put(keyStroke, name);
    }
    /**
     * Scrolls the given component by its unit or block increment in the given direction (actually a scale factor, so use +1 or -1).
     * Useful for implementing behavior like in Apple's Mail where page up/page down in the list cause scrolling in the text.
     */
    public static void scroll(JComponent c, boolean byBlock, int direction) {
        JScrollPane scrollPane = (JScrollPane) SwingUtilities
                .getAncestorOfClass(JScrollPane.class, c);
        JScrollBar scrollBar = scrollPane.getVerticalScrollBar();
        int increment = byBlock ? scrollBar.getBlockIncrement(direction)
                : scrollBar.getUnitIncrement(direction);
        int newValue = scrollBar.getValue() + direction * increment;
        newValue = Math.min(newValue, scrollBar.getMaximum());
        newValue = Math.max(newValue, scrollBar.getMinimum());
        scrollBar.setValue(newValue);
    }
    /**
     * Scrolls the given component to its top or bottom.
     * Useful for implementing behavior like in Apple's Mail where home/end in the list cause scrolling in the text.
     */
    public static void scrollToExtremity(JComponent c, boolean top) {
        JScrollBar scrollBar = ((JScrollPane) SwingUtilities
                .getAncestorOfClass(JScrollPane.class, c))
                .getVerticalScrollBar();
        scrollBar.setValue(top ? scrollBar.getMinimum() : scrollBar
                .getMaximum());
    }
}

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