Repainting JPanel after button click

问题:

I'm new in Java Swing and I have a strange problem to refresh my JPanel.

I create a static JPanel componant in my frame and I call a static method from a FileListenner to repaint my JPanel

 public static void repaintPlan(JPanel f) {
    f.paint(f.getGraphics()); 
    f.revalidate(); // or validate
}

I mean, when I detect change in file content, I calculate the new coordinates and I repaint the JPanel (I create a class exends from JPanel to definepaintComponent()` method)

Everything is working fine when I run the app, and the repaint works when a change data in file; but if I click with my mouse in the Jpanel, the repaint() method doesn't work anymore. Can you tell me why after clicking on JPanel, repainting doesn't work ?

Sorry for my bad english Thanks in advance:)

Edit: Thanks for your repsonses! But even if I use repaint() method, it's the same problem. I'm trying to understand what happens when I click on JPanel. Should I use mouse events in Swing to solve the problem?

回答1:

1) for Swing JComponents is there method paintComponent(), method paint() is for Top-Level Containers (JFrame, JDialog ...) and for AWT Components

2) don't use getGraphics() this method created snapshot that after calling validate, revalidate, repaint expired

3) you have look at tutorial about 2D Graphics, examples here

4) in the case that you'll have real question, please edit your question with SSCCE

回答2:

I'm trying to understand what happens when I click on JPanel. Should I use mouse events in Swing to solve the problem?

You might get some insight from this example that responds to mouse pressed events. In this case, paintComponent() is called automatically when the color is updated. See also Painting in AWT and Swing.

回答3:

No, paintComponent is not called after a mouse press, not unless you've got some code that makes it do this. For example:

import java.awt.*;
import javax.swing.*;

public class MyPanel extends JPanel {
   private static final int PREF_W = 400;
   private static final int PREF_H = 400;

   public MyPanel() {
      setBorder(BorderFactory.createTitledBorder("My Panel"));
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);

      System.out.println("myPanel's paintComponent method has been called");
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   private static void createAndShowGui() {
      MyPanel mainPanel = new MyPanel();

      JFrame frame = new JFrame("MyPanel");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

As you can plainly see, in a plain JPanel, paintComponent is not called after any mouse action unless you change the size of the GUI.

Something else is wrong with your GUI, and also, it shouldn't matter if paintComponent is called once or several times since your program logic should not depend on whether or not this method gets called.

回答4:

I resolve my problem by overriding mouse event methods of my JPanel like this

 myJPanel.addMouseListener(new MouseListener() {

        public void mouseReleased(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        public void mousePressed(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        public void mouseExited(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        public void mouseEntered(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        public void mouseClicked(MouseEvent e) {
            // TODO Auto-generated method stub

        }
    });

thanks