java - 如何使重绘变慢？

Question

我正在制作一个 Java 应用程序，我想知道是否有办法让 jframe 上的重绘速度变慢。让我详细说明一下，该应用程序有一个 jframe 并调用另一个 jframe 来显示必须从一侧移动到另一侧的图形，但它可以以您可以实际看到运动的速度进行。

编辑*为了让我自己清楚，我正在添加一段代码。

import javax.swing.JFrame;
import javax.swing.JLabel;


public class NewJFrame extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jButton1 = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("Start");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jTextArea1.setColumns(20);
        jTextArea1.setRows(5);
        jScrollPane1.setViewportView(jTextArea1);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1)
                .addContainerGap())
            .addGroup(layout.createSequentialGroup()
                .addGap(152, 152, 152)
                .addComponent(jButton1)
                .addContainerGap(191, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(47, 47, 47)
                .addComponent(jButton1)
                .addGap(18, 18, 18)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 149, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(63, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        String position="";
        JFrame frame1=new JFrame();
        JLabel label1=new JLabel();
        label1.setText("Hello!");
        frame1.add(label1);
        frame1.setSize(400,300);
        frame1.setVisible(true);
        for(int i=1;i<20;i++){
            label1.setLocation(i, i);
            frame1.repaint();
            position+="The label is at position: "+label1.getLocation()+"\n";
            jTextArea1.setText(position);
        }
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
               NewJFrame frame= new NewJFrame();
            frame.setLocationRelativeTo(null);
            frame.setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    // End of variables declaration
}

我需要的是让 frame1 显示 label1 定位的动画，并在每次更改时在 textarea 中打印一行位置。谢谢

Answer 1

1. sleep 应严格禁止在 EDT 上
2. 如果您想使用sleep，您应该直接考虑 Swing Timer

现在，如果您想查看如何轻松更改移动元素速度的示例，您不必更改 Swing Timer 的频率，而是实际更改移动元素的速度。 50Hz 的频率通常对人类来说足够了。

这是一个小的演示代码:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.MalformedURLException;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class TestAnimation2 {

    private static final int NB_OF_IMAGES_PER_SECOND = 50;
    private static final int WIDTH = 800;
    private static final int HEIGHT = 600;

    private static final int MIN = 0;
    private static final int MAX = 100;

    private double speed = convert(50);

    private double dx;
    private double dy;

    private double x = WIDTH / 2;
    private double y = HEIGHT / 2;

    private JFrame frame;
    private CirclePanel circle;
    private Runnable job;

    private long lastMove = System.currentTimeMillis();

    protected void initUI() throws MalformedURLException {
        frame = new JFrame(TestAnimation2.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(null);
        circle = new CirclePanel();
        circle.setSize(20, 20);
        frame.add(circle);
        frame.setSize(WIDTH, HEIGHT);
        dx = speed;
        dy = speed;
        final JSlider slider = new JSlider(MIN, MAX);
        slider.addChangeListener(new ChangeListener() {

            @Override
            public void stateChanged(ChangeEvent e) {
                speed = convert(slider.getValue());
                if (dx > 0) {
                    dx = speed;
                } else {
                    dx = -speed;
                }
                if (dy > 0) {
                    dy = speed;
                } else {
                    dy = -speed;
                }

            }
        });
        slider.setValue(50);
        slider.setLocation(0, 0);
        slider.setSize(slider.getPreferredSize());
        frame.add(slider);
        frame.setVisible(true);
        Timer t = new Timer(1000 / NB_OF_IMAGES_PER_SECOND, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                move();
            }
        });
        t.start();
    }

    protected double convert(double sliderValue) {
        return sliderValue + 1;
    }

    protected void move() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                x += dx;
                y += dy;
                if (x + circle.getWidth() > frame.getContentPane().getWidth()) {
                    x = frame.getContentPane().getWidth() - circle.getWidth();
                    dx = -speed;
                } else if (x < 0) {
                    x = 0;
                    dx = speed;
                }
                if (y + circle.getHeight() > frame.getContentPane().getHeight()) {
                    y = frame.getContentPane().getHeight() - circle.getHeight();
                    dy = -speed;
                } else if (y < 0) {
                    y = 0;
                    dy = speed;
                }
                circle.setLocation((int) x, (int) y);
                circle.repaint();
            }
        });
    }

    public static class CirclePanel extends JPanel {

        public CirclePanel() {
            super();
            setOpaque(false);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.fillOval(0, 0, getWidth(), getHeight());
        }
    }

    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException,
            UnsupportedLookAndFeelException {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                try {
                    new TestAnimation2().initUI();
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}