Question

我想知道如何每隔x秒重新绘制和更新JPanel的背景......这是我的代码：

package view;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;

public class GamePanel extends JPanel {

/**
 * 
 */
private static final long serialVersionUID = 1L;
private final JLabel score;
private final static String[] BACKGROUND_COLORS = {"black", "blue", "darkpurple", "purple"};
private int i = 0;

public GamePanel() {
    this.score = new JLabel("Score: ");
    this.score.setBounds(0, 0, 40, 20);
    this.score.setOpaque(false);
    this.score.setForeground(Color.GREEN);
    this.add(score);
}

@Override
protected void paintComponent(final Graphics g) {
    super.paintComponent(g);
    //Image background = new ImageIcon(this.getClass().getResource("/images/" + BACKGROUND_COLORS[i] + "Background.png")).getImage();
    //g.drawImage(background, 0, 0, null);
    Timer timer = new Timer(1000, new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            Image background = new ImageIcon(this.getClass().getResource("/images/" + BACKGROUND_COLORS[i] + "Background.png")).getImage();
            g.drawImage(background, 0, 0, null);
            revalidate();
            repaint();
            System.out.println("trying my timer");
            i++;
            if (i == 4) {
                i = 0;
            }
        }
    });
    timer.start();
}
}

我对此代码有2个问题： 1- JPanel根本没有画画。 2-第一次打印正常，然后每次打印的次数加倍。有什么建议吗？提前谢谢

更新：我用这种方式解决了问题：

package view;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;

public class GamePanel extends JPanel {

/**
 * 
 */
private static final long serialVersionUID = 1L;
private final JLabel score;
private int i = 0;
private final static String[] BACKGROUND_COLORS = {"black", "blue", "darkpurple", "purple"};
private final static int DELAY = 10000;

public GamePanel() {
    this.score = new JLabel("Score: ");
    this.score.setBounds(0, 0, 40, 20);
    this.score.setOpaque(false);
    this.score.setForeground(Color.GREEN);
    this.add(score);
    Timer timer = new Timer(DELAY, new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            i++;
            if (i == 4) {
                i = 0;
            }
        }
    });
    timer.start();
}

@Override
protected void paintComponent(final Graphics g) {
    super.paintComponent(g);
    Image background = new ImageIcon(this.getClass().getResource("/images/" + BACKGROUND_COLORS[this.i] + "Background.png")).getImage();
    g.drawImage(background, 0, 0, null);
    revalidate();
    repaint();
}

更新2：

package view;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;

public class GamePanel extends JPanel {

/**
 * 
 */
private static final long serialVersionUID = 1L;
private final JLabel score;
private int currentImage;
private final List<Image> backgrounds = new ArrayList<>();
private static final String[] BACKGROUND_COLORS = {"black", "blue", "darkpurple", "purple"};
private static final int DELAY = 1000;

public GamePanel() {
    super();
    this.score = new JLabel("Score: ");
    this.score.setBounds(0, 0, 40, 20);
    this.score.setOpaque(false);
    this.score.setForeground(Color.GREEN);
    this.add(score);
    for (final String s : BACKGROUND_COLORS) {
        backgrounds.add(new ImageIcon(this.getClass().getResource("/images/" + s + "Background.png")).getImage());
    }
    final Timer timer = new Timer(DELAY, new ActionListener() {
        @Override
        public void actionPerformed(final ActionEvent e) {
            repaint();
            currentImage++;
            if (currentImage == BACKGROUND_COLORS.length) {
                currentImage = 0;
            }
        }
    });
    timer.start();
}

@Override
protected void paintComponent(final Graphics g) {
    super.paintComponent(g);
    g.drawImage(backgrounds.get(this.currentImage), 0, 0, null);
}

Answer 1

使用Swing Timer，

class GamePanel extends JPanel implements ActionListener{

 Timer timer=new Timer(1000, this);

 public GamePanel() {
   timer.start();// Start the timer here.
 }

 public void actionPerformed(ActionEvent ev){
    if(ev.getSource()==timer){
      repaint();// this will call at every 1 second
    }

}

如何每x秒重绘一次jpanel？

1 个答案: