Java：当计时器处于活动状态时，JSplitPane 将顶部面板的内容复制到底部面板

Question

所以我有一个 JSplitPane 和两个 JPanel - 一个在顶部，一个在底部。在两个面板中，我都覆盖了paintComponent 方法并添加了我自己的图形。在底部面板中，我想添加一个动画。当面板不重新绘制时，这很好，但是一旦 Timer (javax.swing.Timer) 开始调用重新绘制，底部面板就会模仿顶部面板的外观并出现故障。实际动画并未刷新，而是不断添加（就像拖动的画笔而不是移动的对象）。

这是底部面板类的代码：

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);
    }
}

这是 Splitpane 类的代码：

//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();
    }
}

顶部面板有点复杂。它涉及鼠标操作（包括 MouseEntered 侦听器）和动画以与用户鼠标输入进行交互。 奇怪的是，我有另一个底部面板被换掉了，它也使用动画和一个计时器，并且没有这个故障。

任何想法可能导致这种情况？感谢您的所有帮助！

Answer 1

我无法想象你的动画是如何工作的，

1/ 但如果动画取决于Listener 中的任何一个，那么Timer 必须是Timer#restart();

2/ 检查（示例），如何通过addNotify()/removeNotify() 进行启动/停止动画

注意需要全高清显示器以获得更好的输出或更改代码行

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

到

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

例子：

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);
            }
        }
    }
}