Question

So I have a JSplitPane, and two JPanels – one on top, one on the bottom. In both panels I overrode the paintComponent method and added my own graphics. In the bottom panel, I wanted to add an animation. When the panel does not repaint, it’s fine, but as soon as the Timer (javax.swing.Timer) starts to call repaints, the bottom panel mimics the appearance of the top panel and glitches out. The actual animations are not refreshed, but rather it keeps on adding (like a dragged paintbrush instead of a moving object).

Here’s the code for the Bottom Panel class:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.JPanel;
import javax.swing.Timer;

public class WaitControls extends JPanel {

    private int pos;

    public WaitControls(){
        setBackground(Color.gray);
        pos = 0;
    }

    public void progress(){
        //animation timer:
        Timer timer = new Timer(30, new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e) {
                pos++;
                repaint();
            }
        });
        timer.start();
    }

    @Override
    public void paintComponent(Graphics g){
        g.fillRect(pos, pos, 10, 20);
    }
}

And here’s the code for the Splitpane class:

//my classes (imported packages)
import rcc.controls.ControlPanel;
import rcc.controls.InitControls;
import rcc.controls.WaitControls;
import rcc.video.Screen;

import javax.swing.JSplitPane;

public class MainPanel extends JSplitPane{

    public RCC rcc;
    public Screen screen;

    private int height;

    public ControlPanel curPanel;

    public MainPanel(RCC rcc, Screen screen, int height){
        super(JSplitPane.VERTICAL_SPLIT);

        this.rcc = rcc;
        this.screen = screen;
        this.height = height;

        setDividerSize(2);
        setEnabled(false);

        setTopComponent(screen);

        setToInitControls();
    }

    //sets the control panel to init controls ***WORKS FINE***
    public void setToInitControls(){
        InitControls initCtrls = new InitControls(this);
        setBottomComponent(initCtrls);
        curPanel = initCtrls;
        setDividerLocation(height / 4 * 3);
    }

    //sets the control panel to wait controls (trying to connect) ***GLITCHES***
    public void setToWaitControls(){
        WaitControls waitCtrls = new WaitControls();
        setBottomComponent(waitCtrls);
        curPanel = waitCtrls;
        setDividerLocation(height / 4 * 3);
        waitCtrls.progress();
    }
}

The top panel is a bit complicated. It involves mouse action (including a MouseEntered listener) and animates to interact with user mouse input.
The strange thing is, I have another bottom panel that was swapped out that also uses animations, and a timer, and does not have this glitch.

Any ideas what may have caused this? Thank you for all your help!

Answer 1

I can’t imagine how your animations works,

1/ but if animation(s) depends of by any of Listener then Timer must be Timer#restart();

2/ check (example), how to pass addNotify()/removeNotify() for start/stop animatiom(s)

NOTE required fullHD monitor for better output or change code line

for (int iPanels = 0; iPanels < 3; iPanels++) {

to

for (int iPanels = 0; iPanels < 2; iPanels++) {

Example:

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class AnimationBackground {

    public AnimationBackground() {
        Random random = new Random();
        JFrame frame = new JFrame("Animation Background");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setLayout(new GridLayout(0, 3, 10, 10));
        for (int iPanels = 0; iPanels < 3; iPanels++) {
            final MyJPanel panel = new MyJPanel();
            panel.setBackground(Color.BLACK);
            for (int i = 0; i < 50; i++) {
                Star star = new Star(new Point(random.nextInt(490), random.nextInt(490)));
                star.setColor(new Color(100 + random.nextInt(155), 100 + random.nextInt(155), 100 + random.nextInt(155)));
                star.setxIncr(-3 + random.nextInt(7));
                star.setyIncr(-3 + random.nextInt(7));
                panel.add(star);
            }
            panel.setLayout(new GridLayout(10, 1));
            JLabel label = new JLabel("This is a Starry background.", JLabel.CENTER);
            label.setForeground(Color.WHITE);
            panel.add(label);
            JPanel stopPanel = new JPanel();
            stopPanel.setOpaque(false);
            stopPanel.add(new JButton(new AbstractAction("Stop this madness!!") {

                private static final long serialVersionUID = 1L;

                @Override
                public void actionPerformed(ActionEvent e) {
                    panel.stopAnimation();
                }
            }));
            panel.add(stopPanel);
            JPanel startPanel = new JPanel();
            startPanel.setOpaque(false);
            startPanel.add(new JButton(new AbstractAction("Start moving...") {

                private static final long serialVersionUID = 1L;

                @Override
                public void actionPerformed(ActionEvent e) {
                    panel.startAnimation();
                }
            }));
            panel.add(startPanel);
            frame.add(panel);
        }
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

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

            @Override
            public void run() {
                AnimationBackground animationBackground = new AnimationBackground();
            }
        });
    }

    class Star extends Polygon {

        private static final long serialVersionUID = 1L;
        private Point location = null;
        private Color color = Color.YELLOW;
        private int xIncr, yIncr;
        static final int WIDTH = 500, HEIGHT = 500;

        Star(Point location) {
            int x = location.x;
            int y = location.y;
            this.location = location;
            this.addPoint(x, y + 8);
            this.addPoint(x + 8, y + 8);
            this.addPoint(x + 11, y);
            this.addPoint(x + 14, y + 8);
            this.addPoint(x + 22, y + 8);
            this.addPoint(x + 17, y + 12);
            this.addPoint(x + 21, y + 20);
            this.addPoint(x + 11, y + 14);
            this.addPoint(x + 3, y + 20);
            this.addPoint(x + 6, y + 12);
        }

        public void setColor(Color color) {
            this.color = color;
        }

        public void move() {
            if (location.x < 0 || location.x > WIDTH) {
                xIncr = -xIncr;
            }
            if (location.y < 0 || location.y > WIDTH) {
                yIncr = -yIncr;
            }
            translate(xIncr, yIncr);
            location.setLocation(location.x + xIncr, location.y + yIncr);
        }

        public void setxIncr(int xIncr) {
            this.xIncr = xIncr;
        }

        public void setyIncr(int yIncr) {
            this.yIncr = yIncr;
        }

        public Color getColor() {
            return color;
        }
    }

    class MyJPanel extends JPanel {

        private static final long serialVersionUID = 1L;
        private ArrayList<Star> stars = new ArrayList<Star>();
        private Timer timer = new Timer(20, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                for (Star star : stars) {
                    star.move();
                }
                repaint();
            }
        });

        public void stopAnimation() {
            if (timer.isRunning()) {
                timer.stop();
            }
        }

        public void startAnimation() {
            if (!timer.isRunning()) {
                timer.start();
            }
        }

        @Override
        public void addNotify() {
            super.addNotify();
            timer.start();
        }

        @Override
        public void removeNotify() {
            super.removeNotify();
            timer.stop();
        }

        MyJPanel() {
            this.setPreferredSize(new Dimension(520, 520));
        }

        public void add(Star star) {
            stars.add(star);
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            ((Graphics2D) g).setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            for (Star star : stars) {
                g.setColor(star.getColor());
                g.fillPolygon(star);
            }
        }
    }
}