一個(gè)極其簡(jiǎn)單的實(shí)現(xiàn).

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();

}

});

}

}

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