Show button on JLabel in Swing

问题:

I have a JPanel with GroupLayout with 3 JLabels in it. I also have a hidden JButton in it.

I have added a MouseListener to JPanel showing the button in mouseEntered and hide the button in mouseExited events respectively.

At this time, their is space for button between 2 labels and their only the button is shown or hidden using setVisible(). When the btn is visible, the labels below it goes down making space for button and if the btn is hidden it again comes to its original size.

What I want - in mouseEntered, the button should show on the label itself (let it be overlap) and I should be able to click on the button. This all should happen very smoothly without screen flickering. Similarly in mouseExited, the button should be removed.

How do I achieve this ? Can anyone help me with this.

UPDATE @Andrew, Thanks I tried with JLayeredPane and it does work. Though the button is not set to visible false. Here's my mouseMoved code :

public void mouseMoved(MouseEvent e) {
    if (e.getComponent() == layeredPane) {
        if (! startCustomBtn.isVisible())
            startCustomBtn.setVisible(true);
        startCustomBtn.setLocation(e.getX()-55, e.getY()-30);       
    } else {
        if (startCustomBtn.isVisible()) {
            startCustomBtn.setVisible(false);
            revalidate();
        }
    }
}

Layout of the JPanel :

private void layeredLayout() {
    layeredPane = new JLayeredPane();
    layeredPane.addMouseMotionListener(this);

    Insets insets = this.getInsets();
    Dimension size = rateLabel.getPreferredSize();
    rateLabel.setBounds(insets.left + 45, insets.top + 15, size.width, size.height);
    size = imageLabel.getPreferredSize();
    imageLabel.setBounds(insets.left + 15, insets.top + 40, size.width, size.height);

    size = label.getPreferredSize();
    label.setBounds(insets.left + 45, insets.top + imageLabel.getWidth() + 20 , size.width, size.height);

    size = startCustomBtn.getPreferredSize();
    startCustomBtn.setBounds(insets.left + 45, insets.top + 40 + size.height, size.width, size.height);

    layeredPane.add(rateLabel, new Integer(0));
    layeredPane.add(imageLabel, new Integer(1));
    layeredPane.add(label, new Integer(2));

    layeredPane.add(startCustomBtn, new Integer(1), 0);

    setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
    add(layeredPane);
}

Strange - I tried the layout with null, FlowLayout, but couldn't see anything. When tried with BoxLayout, components showed up.

REsult :

Main screen has a JPanel with Gridlayout(2, 3) and in each cell this JPanel (MyPanel) is added. When I come out from 1 cell (i.e. MyPanel) the button of that panel should be hidden which is not happening with the above code. What can be the reason ? I also added revalidate() & also repaint() but nothing works. ????

回答1:

What I want - in mouseEntered, the button should show on the label itself (let it be overlap) and I should be able to click on the button. This all should happen very smoothly without screen flickering. Similarly in mouseExited, the button should be removed.

As JLabel extends from JComponent you can add componentes to label itself, just need to set a LayoutManager first. This fact is well explained in this question.

Sample Code

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.LineBorder;

public class Demo {

   private void initGUI(){

       final JButton button = new JButton("Hello!");
       button.setVisible(false);

       final JLabel testLabel = new JLabel("Welcome!");
       testLabel.setPreferredSize(new Dimension(200, 30));
       testLabel.setBorder(new LineBorder(Color.GRAY, 1));
       testLabel.setLayout(new BorderLayout());
       testLabel.add(button, BorderLayout.EAST);

       button.addMouseListener(new MouseAdapter() {
           @Override
           public void mouseExited(MouseEvent e) {
               Point mousePosition = MouseInfo.getPointerInfo().getLocation();
               if(testLabel.contains(mousePosition)){
                   testLabel.dispatchEvent(new MouseEvent(testLabel, MouseEvent.MOUSE_ENTERED, System.currentTimeMillis(), 0, mousePosition.x, mousePosition.y, 0, false));
               } else {
                   testLabel.dispatchEvent(new MouseEvent(testLabel, MouseEvent.MOUSE_EXITED, System.currentTimeMillis(), 0, mousePosition.x, mousePosition.y, 0, false));
               }
           }

       });

       button.addActionListener(new ActionListener() {
           @Override
           public void actionPerformed(ActionEvent e) {
               JOptionPane.showMessageDialog(null, "The button was pressed!");
               Point mousePosition = MouseInfo.getPointerInfo().getLocation();
               testLabel.dispatchEvent(new MouseEvent(testLabel, MouseEvent.MOUSE_EXITED, System.currentTimeMillis(), 0, mousePosition.x, mousePosition.y, 0, false));
           }
       });

       testLabel.addMouseListener(new MouseAdapter(){
           @Override
           public void mouseEntered(MouseEvent e) {
               JLabel label = (JLabel) e.getSource();
               label.setText("Here is the Button!");
               button.setVisible(true);
           }

           @Override
           public void mouseExited(MouseEvent e) {
               Point point = e.getPoint();
               point.setLocation(point.x - button.getX(), point.y - button.getY()); //make the point relative to the button's location
               if(!button.contains(point)) {
                   JLabel label = (JLabel) e.getSource();
                   label.setText("The button is gone!");
                   button.setVisible(false);
               }
           }
       }); 

       JPanel content = new JPanel(new FlowLayout());
       content.setPreferredSize(new Dimension(300,100));
       content.add(testLabel);

       JFrame frame = new JFrame("Demo");
       frame.setContentPane(content);
       frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
       frame.pack();
       frame.setLocationRelativeTo(null);
       frame.setVisible(true);

   }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Demo().initGUI();
            }
        });
    }    

}

Output

Update

As @nIcEcOw pointed out (thanks!), there's an annoying flickering generated by mouse events' transition. I improved the example fixing this and another untreated aspects like "what happens when mouse exits from JButton?"

回答2:

Questions like this are kind of frustrating. There is almost enough information to describe what you want, or what the problem is, but not quite.

It seems that you want label-label-label until the mouse enters the panel, then you want the appearance to be label-button-label. It's hard to imagine me wanting a UI to act like this.

Is there something about the appearance of the button you don't like, that you want it only to appear on mouse-over-panel? Can the button's appearance be altered so that it looks the way you want it to look, without all this hocus-pocus with the middle label and the button?

I don't have any idea why you mention a timer -- nothing that you describe is being timed, as near as I can tell. In addition, you should be able to boil down what you have to a small runnable example and post it, so that someone can see what you've got and what it does.