一个极其简单的实现.
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
class ShowPreviews {
class ToolTipListener extends MouseAdapter {
JWindow toolTip;
JLabel label;
Component preview;
ToolTipListener(Component preview) {
this.preview = preview;
}
@Override
public void mouseEntered(MouseEvent me) {
if (toolTip==null) {
toolTip = new JWindow();
label = new JLabel();
toolTip.add(label);
}
label.setIcon( new ImageIcon(
getScaledImageOfComponent(preview, .6) ) );
toolTip.pack();
Component c = (Component)me.getSource();
int x = c.getLocationOnScreen().x+(c.getWidth()/2);
int y = c.getLocationOnScreen().y+c.getHeight();
toolTip.setLocation(x,y);
toolTip.setVisible(true);
}
@Override
public void mouseExited(MouseEvent me) {
toolTip.setVisible(false);
toolTip.dispose();
}
public Image getScaledImageOfComponent(
Component component, double scale) {
BufferedImage bi = new BufferedImage(
(int)(component.getWidth()*scale),
(int)(component.getHeight()*scale),
BufferedImage.TYPE_INT_RGB);
Graphics2D g = bi.createGraphics();
g.scale(scale, scale);
component.paint(g);
g.dispose();
return bi;
}
}
ShowPreviews() {
JPanel gui = new JPanel(new BorderLayout(2,2));
final CardLayout cards = new CardLayout();
final JPanel cardPanel = new JPanel(cards);
JPanel treePanel = new JPanel();
JTree tree = new JTree();
tree.setVisibleRowCount(5);
tree.expandRow(2);
treePanel.add(new JScrollPane(tree));
cardPanel.add(treePanel, "tree");
JPanel labelPanel = new JPanel(new GridLayout(0,1,2,2));
for (int ii=1; ii<7; ii++) {
labelPanel.add(new JLabel("Label " + ii));
}
cardPanel.add(new JScrollPane(labelPanel), "label");
JToolBar uiSelectors = new JToolBar();
// we should use a ButtonGroup for the cards,
// but plain buttons look better on hover.
JButton treeButton = new JButton("Tree");
treeButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae) {
cards.show(cardPanel, "tree");
}
});
uiSelectors.add(treeButton);
treeButton.addMouseListener( new ToolTipListener(treePanel));
JButton labelButton = new JButton("Label");
labelButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ae) {
cards.show(cardPanel, "label");
}
});
uiSelectors.add(labelButton);
labelButton.addMouseListener( new ToolTipListener(labelPanel));
gui.add(uiSelectors, BorderLayout.NORTH);
gui.add(cardPanel, BorderLayout.CENTER);
JOptionPane.showMessageDialog(null, gui);
}
public static void main(String[] args) {
// start the GUI on the EDT
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new ShowPreviews();
}
});
}
}
