How to make JSplitPane auto expand on mouse hover?

问题

I want to make a Java program with Swing layout where there is a menu on the left that is expanded when a mouse hovers over the menu area, but auto contracts after your mouse leaves.

I am trying to imitate the effect of something like mobile Youtube for Android, or Weebly's editor. Fro those who don't know, both layouts have menus on the left that expand when your mouse hovers over them. Then after your mouse leaves the area, the menu contracts again and is out of view.

I was able to create the JSplitPane containing my menu successfully, but I have no idea how to make it automatically expand when the user's mouse hovers over the JSplitPane component, or how to make it contract after the mouse leaves the area.

In case anyone is wondering why: This type of menu is easy for the user to use but because it hides away when unneeded, allows me to have more space for the main part of the program.

Any help would be appreciated thanks!

回答1:

Well make use of jSplitPan.setDividerLocation(location);: Sets the location of the divider. location - an int specifying a UI-specific value (typically a pixel count).

jSplitPane1.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent evt) {
                // use evt.getSource() if needed
                jSplitPan1.setDividerLocation(location);
            }
        });

You will probably need to compute the divider location a little bit intelligently. hints: by computing the relevant preferred-size hints. The part relevant should be discovered by you.

Take a look into official tutorial page to know: How to use MouseMotionListeners including other event listeners.

回答2:

There are two basic problems...

You need to detect when the mouse hovers over the divider and
When it exists the "menu"

The second is relatively easy, you can use a MouseListener and monitor the mouseExit event, setting the position of the split pane divider as the mouse leaves.

This is complicated though, as if the user exists the "menu" by crossing over the divider, this may trigger the "menu" to made visible again...

The first problem is more complicated, as the JSplitPane contains three components, the left and right components, but also a divider component. JSplitPane doesn't actually allow access to the divider, which is rather annoying and because it uses it's own mouse listener, it blocks mouse events going to the split itself.

Instead, you need to gain access to it via the UI delegate.

Once you've set up the mouse listener, you need to ensure that the menu will only be shown when the menu is hidden, for this, I simply checked the size of the "menu" component

For example...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSplitPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.plaf.basic.BasicSplitPaneDivider;
import javax.swing.plaf.basic.BasicSplitPaneUI;

public class TestSpltPane {

    public static void main(String[] args) {
        new TestSpltPane();
    }

    public TestSpltPane() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                final JPanel left = new JPanel();
                left.setBackground(Color.RED);
                left.setPreferredSize(new Dimension(100, 100));
                JPanel right = new JPanel();
                right.setBackground(Color.BLUE);
                right.setPreferredSize(new Dimension(100, 100));
                final JSplitPane sp = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, left, right);
                sp.setDividerLocation(0);

                BasicSplitPaneDivider divider = ((BasicSplitPaneUI) sp.getUI()).getDivider();
                divider.addMouseListener(new MouseAdapter() {

                    @Override
                    public void mouseEntered(MouseEvent e) {
                        if (left.getWidth() == 0) {
                            sp.setDividerLocation(100);
                        }
                    }

                });

                left.addMouseListener(new MouseAdapter() {

                    @Override
                    public void mouseExited(MouseEvent e) {
                        sp.setDividerLocation(0);
                    }

                });

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(sp);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

}

来源：https://stackoverflow.com/questions/20251123/how-to-make-jsplitpane-auto-expand-on-mouse-hover

标签

java

swing

mouseevent

jscrollpane

jsplitpane