如果鼠标静止，Java Canvas 的 fps 较低

Question

如果我没有以某种方式更新屏幕，对 canvas.repaint() 的几次调用似乎会被完全跳过。移动鼠标时，一切都很好。

我的代码如下:

package yeet.gfxTut;

import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;

import javax.swing.JFrame;

public class Toot extends Canvas {
    private static final long serialVersionUID = 1L;
    public static int xPos, yPos, yV, xV;

    public static void main(String[] args) throws InterruptedException {
        Random rand = new Random();
        JFrame frame = new JFrame("My Drawing");
        Canvas canvas = new Toot();
        canvas.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.add(canvas);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        canvas.addMouseListener(new Toot().new TootMListener());
        xPos = rand.nextInt(400);
        yPos = rand.nextInt(400);
        xV = rand.nextInt(5) + 1;
        yV = rand.nextInt(5) + 1;
        while (true) {
            Thread.sleep(1000 / 60);
            canvas.repaint();
        }
    }

    public void paint(Graphics g) {
        Random rand = new Random();
        if (xPos < 0) {
            xV += rand.nextInt(2) - 1;
            xV = 0 - xV;
        }
        if (yPos < 0) {
            yV += rand.nextInt(2) - 1;
            yV = 0 - yV;
        }
        if (xPos > 400) {
            xV += rand.nextInt(2) - 1;
            xV = 0 - xV;
        }
        if (yPos > 400) {
            yV += rand.nextInt(2) - 1;
            yV = 0 - yV;
        }
        xPos += xV;
        yPos += yV;
        g.fillOval(xPos, yPos, 6, 6);
    }

    private class TootMListener implements MouseListener {
        Random rand = new Random();

        @Override
        public void mouseClicked(MouseEvent e) {
            xV = rand.nextInt(5) + 1;
            yV = rand.nextInt(5) + 1;
        }

        @Override
        public void mousePressed(MouseEvent e) {

        }

        @Override
        public void mouseReleased(MouseEvent e) {

        }

        @Override
        public void mouseEntered(MouseEvent e) {

        }

        @Override
        public void mouseExited(MouseEvent e) {

        }

    }
}

我在多个不同的 canvas 项目中遇到了这个问题，有什么帮助吗？

更新:我尝试使用建议的答案，但导致了同样的问题。新代码如下:

package yeet.gfxTut;

import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.Timer;

public class Toot extends Canvas implements ActionListener {
    private static final long serialVersionUID = 1L;
    public static int xPos, yPos, yV, xV;

    Timer timer = new Timer(1000/60, this);
    public Toot() {
        super();
        timer.start();
    }
    public static void main(String[] args) throws InterruptedException {
        // timer.start();
        Random rand = new Random();
        JFrame frame = new JFrame("My Drawing");
        Canvas canvas = new Toot();
        canvas.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.add(canvas);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        canvas.addMouseListener(new Toot().new TootMListener());
        xPos = rand.nextInt(400);
        yPos = rand.nextInt(400);
        xV = rand.nextInt(5) + 1;
        yV = rand.nextInt(5) + 1;
        while (true) {
            Thread.sleep(1000 / 60);
            canvas.repaint();
        }
    }

    public void paint(Graphics g) {
        Random rand = new Random();
        if (xPos < 0) {
            xV += rand.nextInt(2) - 1;
            xV = 0 - xV;
        }
        if (yPos < 0) {
            yV += rand.nextInt(2) - 1;
            yV = 0 - yV;
        }
        if (xPos > 400) {
            xV += rand.nextInt(2) - 1;
            xV = 0 - xV;
        }
        if (yPos > 400) {
            yV += rand.nextInt(2) - 1;
            yV = 0 - yV;
        }
        xPos += xV;
        yPos += yV;
        g.fillOval(xPos, yPos, 6, 6);
    }

    private class TootMListener implements MouseListener {
        Random rand = new Random();

        @Override
        public void mouseClicked(MouseEvent e) {
            xV = rand.nextInt(5) + 1;
            yV = rand.nextInt(5) + 1;
        }

        @Override
        public void mousePressed(MouseEvent e) {

        }

        @Override
        public void mouseReleased(MouseEvent e) {

        }

        @Override
        public void mouseEntered(MouseEvent e) {

        }

        @Override
        public void mouseExited(MouseEvent e) {

        }

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // if(e.getSource() == timer){
            repaint();
        // }
    }
}

Answer 1

引用第一段代码，而不是

while (true) {
    Thread.sleep(1000 / 60);
    canvas.repaint();
}

使用 Swing 包中的Timer:

new javax.swing.Timer(1000/60,event->canvas.repaint()).start();

我已经上过你的类(class)，并且进展顺利:

public class Toot extends Canvas {
    private static final long serialVersionUID = 1L;
    public static int xPos, yPos, yV, xV;

    public static void main(String[] args) throws InterruptedException {
        Random rand = new Random();
        JFrame frame = new JFrame("My Drawing");
        Canvas canvas = new Toot();
        canvas.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.add(canvas);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        canvas.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent e) {
                xV = rand.nextInt(5) + 1;
                yV = rand.nextInt(5) + 1;
            }
        });
        xPos = rand.nextInt(400);
        yPos = rand.nextInt(400);
        xV = rand.nextInt(5) + 1;
        yV = rand.nextInt(5) + 1;
        new javax.swing.Timer(1000/60,e->canvas.repaint()).start();
    }

    @Override
    public void paint(Graphics g) {
        Random rand = new Random();
        if (xPos < 0) {
            xV += rand.nextInt(2) - 1;
            xV = Math.abs(xV);
        }
        if (yPos < 0) {
            yV += rand.nextInt(2) - 1;
            yV = Math.abs(yV);
        }
        if (xPos > 400) {
            xV += rand.nextInt(2) - 1;
            xV = - Math.abs(xV);
        }
        if (yPos > 400) {
            yV += rand.nextInt(2) - 1;
            yV = - Math.abs(yV);
        }
        xPos +=xV;
        yPos +=yV;
        g.fillOval(xPos, yPos, 6, 6);
    }
}