动画构造函数在 Java GUI 中不起作用

Question

您好，我是 Java GUI 新手，我制作了 second.java，如下所示：

package theproject;
import java.awt.event.*;
import java.awt.*;

import javax.swing.*;

public class second extends JPanel implements ActionListener {
private Timer animator;
private ImageIcon imageArray[];
private int delay=50, totalFrames=8, currentFreames=1;

public second()
{
  imageArray= new ImageIcon[totalFrames];
  System.out.println(imageArray.length);
  for(int i=0; i<imageArray.length;i++)
  {
      imageArray[i]=new ImageIcon(i+1+".png");
      System.out.println(i+1);

  }
  animator= new Timer(delay, this);
  animator.start();

   }

  public void paintComponent(Graphics g )
  {
  super.paintComponent(g);
   if(currentFreames<8)
   {

  imageArray[currentFreames].paintIcon(this, g, 0, 0);
  currentFreames++;
  System.out.println(currentFreames);
}
else{
    currentFreames=0;
}
  }

@Override
public void actionPerformed(ActionEvent arg0) {

    repaint();
}

 }

第二个调用构造函数的 Gui 没有显示输出。你能指导我该怎么做吗，下面给出了gui：

   package theproject;

 import java.awt.EventQueue;

 import javax.swing.JFrame;
 import javax.swing.JButton;
 import java.awt.BorderLayout;
 import java.awt.event.ActionListener;
 import java.awt.event.ActionEvent;
 import javax.swing.SwingConstants;
 import javax.swing.JTextField;

  public class Sav {

private JFrame frame;
private JTextField textField;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Sav window = new Sav();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the application.
 */
public Sav() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frame = new JFrame();
    frame.setBounds(100, 100, 450, 300);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().setLayout(null);

    textField = new JTextField();
    textField.setBounds(10, 0, 261, 20);
    frame.getContentPane().add(textField);
    textField.setColumns(10);

    JButton btnNewButton = new JButton("Submit");
    btnNewButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
        second s= new second();
         frame.add(s);
        }
    });
    btnNewButton.setBounds(273, -1, 89, 23);
    frame.getContentPane().add(btnNewButton);

}
}

gui 必须基本上调用构造函数，它将在屏幕上展示动画如果有人我做错了什么或必须做的事情，请告诉我。

Answer 1

首先，不要在paintComponent 方法中更新状态，因为多种原因随时可能发生绘制，大多数情况下无需您的交互。绘画应该简单地描绘当前状态。在您的ActionListener 中，您应该推进框架并决定应该发生什么（例如重置框架值）

其次，您实际上从未将second 添加到任何内容中，因此它永远不会显示。

第三，您不要在second 中覆盖getPreferredSize，因此布局管理器将不知道组件的大小，而只会分配0x0，使其与不可见一样好区别

第四，您正在使用null 布局。这会让你的生活变得无比艰难。 Swing 围绕布局管理器的使用进行了设计和优化，它们在决定如何最好地处理不同渲染系统/管道中字体指标的差异方面发挥了重要作用，我强烈建议您花时间学习如何使用它们

第五，paintComponent与public没有业务关系，任何人都不应该直接调用它

示例

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;

public class Sav {

    private JFrame frame;
    private JTextField textField;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Sav window = new Sav();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Sav() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = GridBagConstraints.REMAINDER;

        textField = new JTextField(20);
        frame.getContentPane().add(textField, gbc);

        JButton btnNewButton = new JButton("Submit");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                second s = new second();
                frame.add(s, gbc);
                frame.getContentPane().revalidate();
                frame.pack();
                frame.setLocationRelativeTo(null);
            }
        });
        frame.getContentPane().add(btnNewButton, gbc);

        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public class second extends JPanel implements ActionListener {

        private Timer animator;
        private ImageIcon imageArray[];
        private int delay = 50, totalFrames = 8, currentFreames = 1;

        public second() {
            imageArray = new ImageIcon[totalFrames];
            for (int i = 0; i < imageArray.length; i++) {
                imageArray[i] = new ImageIcon(getImage(i));

            }
            animator = new Timer(delay, this);
            animator.start();

        }

        protected Image getImage(int index) {
            BufferedImage img = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = img.createGraphics();
            FontMetrics fm = g2d.getFontMetrics();
            g2d.dispose();
            String text = Integer.toString(index);
            int height = fm.getHeight();
            int width = fm.stringWidth(text);

            img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
            g2d = img.createGraphics();
            g2d.setColor(getForeground());
            g2d.drawString(text, 0, fm.getAscent());
            g2d.dispose();
            return img;
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(imageArray[0].getIconWidth(), imageArray[1].getIconHeight());
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            imageArray[currentFreames].paintIcon(this, g, 0, 0);
        }

        @Override
        public void actionPerformed(ActionEvent arg0) {
            currentFreames++;
            if (currentFreames >= imageArray.length) {
                currentFreames = 0;
            }
            repaint();
        }

    }
}

您的代码也无法正常工作。它增加图像集的值但不显示图像

对我来说很好用……

imageArray[i]=new ImageIcon(i+1+".png"); 如果由于某种原因无法加载图像，则不会产生任何错误（它会在后台线程中加载图像，这只是另一个问题）。

相反，我建议改用ImageIO.read，如果由于某种原因无法读取图像，它将抛出IOException，这非常有用。详情请见Reading/Loading an Image