如何使用Swing JPanel在Java中強制重繪？

Question

為什么不為簡單的動畫重新繪制圖像？ 我從兩種不同的方法調用repaint（），一種導致重新繪制，而另一種則沒有。 確實重繪的方法是從事件偵聽器生成的。 沒有的是定時動畫線程。 我知道動畫線程正在正確運行，並且只要我不斷滑動滑塊，它就可以完美顯示。 請幫助！
PS：是的，我在這里看到了許多類似的問題，並且嘗試了驗證，重新驗證以及使用paint vs paintComponent。 組成代碼的四個類如下：

import javax.swing.*;

public class gutz{

    public static int windowWidth = 640;
    public static int windowHeight = 480;

    public static void main(String[] args){

        hBod hb1 = new hBod(50, 30, 21, 111, 7, -11);   //mass, radius, xpos, ypos, xvel, yvel
        Thread t1 = new Thread(hb1);

        windowmakr w = new windowmakr();
        w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        w.setSize(windowWidth, windowHeight);
        w.setVisible(true);

        t1.start();
    }
}

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

public class windowmakr extends JFrame {

    private JSlider slider;
    private drawr panel;

    public windowmakr(){
        super("Orbit Explorer");
        panel = new drawr();
        panel.setBackground(Color.BLACK);

        slider = new JSlider(SwingConstants.HORIZONTAL, 0, 200, 10);
        slider.setMajorTickSpacing(10);
        slider.setPaintTicks(true);

        slider.addChangeListener(
                new ChangeListener(){
                    public void stateChanged(ChangeEvent e){
                        panel.setSpeed(slider.getValue());
                    }
                }
        );

        add(slider, BorderLayout.SOUTH);
        add(panel, BorderLayout.CENTER);

    }

}

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

public class drawr extends JPanel{

    private int diameter = 10;
    private static int rad;
    private static int xpos;
    private static int ypos;

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.setColor(Color.ORANGE);
        g.fillOval((gutz.windowWidth-diameter)/2, ((gutz.windowHeight-diameter)/2)-40, diameter, diameter);
        g.setColor(Color.CYAN);
        g.fillOval(xpos, ypos, rad, rad);

    }

/*  public void paint(Graphics g){
        super.paint(g);
        g.setColor(Color.ORANGE);
        g.fillOval((gutz.windowWidth-diameter)/2, ((gutz.windowHeight-diameter)/2)-40, diameter, diameter);
        g.setColor(Color.CYAN);
        g.fillOval(xpos, ypos, rad, rad);   
    }
*/  
    public void setSpeed(int newD){
        diameter = (newD >= 0 ? newD : 10);
        repaint();
    }

    public void renderImage(int r, int xp, int yp){
        rad=r;
        xpos=xp;
        ypos=yp;
        repaint();
    }

    public Dimension getPreferredSize(){
        return new Dimension(200,200);
    }

    public Dimension getMinimumSize(){
        return getPreferredSize();
    }
}

public class hBod implements Runnable{

    private int mass;
    private int rad;
    private int xpos;
    private int ypos;
    private double xvel;
    private double yvel;

    public drawr render;

    public hBod(int m, int r, int xp, int yp, double xv, double yv){
        mass=m;
        rad=r;
        xpos=xp;
        ypos=yp;
        xvel=xv;
        yvel=yv;

        render = new drawr();
    }

    public void run(){
        try{
            while(true){
                xpos+=xvel;
                ypos+=yvel;
                yvel+=1;
                System.out.printf("rad - %d, xpos - %d, ypos - %d\n", rad, xpos, ypos);
                render.renderImage(rad, xpos, ypos);

                Thread.sleep(1000);
            }
        }catch(Exception e){}
    }
}

Answer 1

就像我之前說的，問題出在這一行render = new drawr(); 在hBod構造函數中。 在gutz類中創建一個像private drawr panel = new drawr()的gutz ，然后使用其構造函數將其傳遞給其他兩個類，例如hBod hb1 = new hBod(50, 30, 21, 111, 7, -11, panel)和windowmakr w = new windowmakr(panel)和簡單地使用該引用指向panel.renderImage(...)內hBod類和panel.setSpeed(...)從windowmakr類。

這是修改后的代碼，請學習Java編碼約定：

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

public class Gutz {

    public static int windowWidth = 640;
    public static int windowHeight = 480;

    public static void main(String[] args){
        Drawr panel = new Drawr();
        panel.setBackground(Color.BLACK);
        HBod hb1 = new HBod(50, 30, 21, 111, 7, -11, panel);   //mass, radius, xpos, ypos, xvel, yvel
        Thread t1 = new Thread(hb1);

        WindowMakr w = new WindowMakr(panel);
        w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        w.setSize(windowWidth, windowHeight);
        w.setVisible(true);

        t1.start();
    }
}

class WindowMakr extends JFrame {

    private JSlider slider;
    private Drawr panel;    

    public WindowMakr(Drawr p){
        super("Orbit Explorer");
        final Drawr panel = p;        

        slider = new JSlider(SwingConstants.HORIZONTAL, 0, 200, 10);
        slider.setMajorTickSpacing(10);
        slider.setPaintTicks(true);

        slider.addChangeListener(
                new ChangeListener(){
                    public void stateChanged(ChangeEvent e){
                        panel.setSpeed(slider.getValue());
                    }
                }
        );

        add(slider, BorderLayout.SOUTH);
        add(panel, BorderLayout.CENTER);

    }

}

class Drawr extends JPanel{

    private int diameter = 10;
    private static int rad;
    private static int xpos;
    private static int ypos;

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.setColor(Color.ORANGE);
        g.fillOval((Gutz.windowWidth-diameter)/2, ((Gutz.windowHeight-diameter)/2)-40, diameter, diameter);
        g.setColor(Color.CYAN);
        g.fillOval(xpos, ypos, rad, rad);

    }

    public void setSpeed(int newD){
        diameter = (newD >= 0 ? newD : 10);
        repaint();
    }

    public void renderImage(int r, int xp, int yp){
        rad=r;
        xpos=xp;
        ypos=yp;
        repaint();
    }

    public Dimension getPreferredSize(){
        return new Dimension(200,200);
    }

    public Dimension getMinimumSize(){
        return getPreferredSize();
    }
}

class HBod implements Runnable{

    private int mass;
    private int rad;
    private int xpos;
    private int ypos;
    private double xvel;
    private double yvel;

    public Drawr render;

    public HBod(int m, int r, int xp, int yp, double xv, double yv, Drawr panel){
        mass=m;
        rad=r;
        xpos=xp;
        ypos=yp;
        xvel=xv;
        yvel=yv;

        render = panel;
    }

    public void run(){
        try{
            while(true){
                xpos+=xvel;
                ypos+=yvel;
                yvel+=1;
                System.out.printf("rad - %d, xpos - %d, ypos - %d\n", rad, xpos, ypos);
                render.renderImage(rad, xpos, ypos);

                Thread.sleep(1000);
            }
        }catch(Exception e){}
    }
}

Answer 2

您可以在JFrame類中使用getContentPane（）。repaint（）方法