java - 球不动；线？

Question

这是一个让球以对角线方式下降的 UI，但球保持静止；线程似乎无法正常工作。你能告诉我如何让球移动吗？

请下载一个球并更改目录，以便程序可以找到您的球的分配位置。没有必要下载足球场，但如果您愿意，也可以。最后，我要感谢您花时间寻找这个故障。

import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.geom.Rectangle2D;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import java.io.File;

class Animation extends JFrame implements ActionListener {  //Frame and listener

  Rectangle2D dimensions = new Rectangle2D.Double(0,0,850,595);  //Not implemented limits
  JButton animate, stop;
  Runnable runnable;
  Thread move;

    public Animation() {
      setLayout(new BorderLayout());  //BorderLayout disposition
      setTitle("Pelota en acción");      

        animate = new JButton("Animate it!");  //Button to create balls
          animate.setBounds(0,0,120,30);
          animate.addActionListener(new ActionListener(){
            @Override
              public void actionPerformed(ActionEvent e) {
                Image ball = null;
                new Layout().createEllipse(ball);
                runnable = new Layout();
                move = new Thread(runnable);
                  move.start();
               }
          });

          stop = new JButton("Freeze");  //Button to interrupt thread (not implemented)
          stop.setBounds(0,0,120,30);
          stop.addActionListener(new ActionListener(){
            @Override
              public void actionPerformed(ActionEvent e) {
                  move.interrupt();
                  Layout.running = false;
              }
          });

        JPanel subPanel = new JPanel();  //Layout with its buttons situated to the south
          subPanel.add(animate);
          subPanel.add(stop);
        add(subPanel,BorderLayout.SOUTH);

        add(new Layout());
    }

    public static void main(String[] args) {
        Animation ventana = new Animation();
          ventana.setSize(850,625);
          ventana.setLocationRelativeTo(null);
          ventana.setVisible(true);
          ventana.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

  @Override
    public void actionPerformed(ActionEvent e) {} //Tag
}  //Class close


class Layout extends JPanel implements Runnable {  //Layout and thread

  int X,Y;  //Coordenadas
  static boolean running = true;  //"To interrupt the thread" momentaneously.
  static ArrayList<Image> balls = new ArrayList<>();  //Balls collection

  @Override
    public void run () {  //Just moves ball towards Narnia xd
        while(running) {
          X++; Y++;
            System.out.println(X+" "+Y);
            repaint();
            updateUI();
            try {
              Thread.sleep(4);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }

  @Override
     public void paintComponent(Graphics g) {
      super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.addRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON));
          repaint();
          updateUI();

        try {
            URL url = new URL("https://www.freejpg.com.ar/image-900/9c/9ca2/F100004898-textura_pasto_verde_linea_de_cal.jpg");
            Image picture = ImageIO.read(url);
              g.drawImage(picture,0,0,null);
        } catch(IOException e){
            System.out.println("URL image was not found");
        }
        finally {
          try {     
        //----------------------------------------------------------------------------
              Image picture = ImageIO.read(new File("C:\\Users\\Home\\Desktop\\Cancha.jpg")); //Pitch
        //----------------------------------------------------------------------------    
                g.drawImage(picture, 0, 0, null);
          } catch (IOException ex) {
              System.out.println("Pitch image was not found");
          }
        }

        for (Image ball : balls) {  //I add balls to the Layout
          g2.drawImage(ball,X,Y,100,100,null);
        }
    }

    public void createEllipse (Image ball) {  //Method that adds balls to the collection
        try {
        //--------------------------------------------------------------------   Ball
            ball = ImageIO.read(new File("C:\\Users\\Home\\Desktop\\Pelota.png"));  //Change this
       //--------------------------------------------------------------------   Ball
        } catch(IOException ex) {
            System.out.println("Any balls were found");
        }
        balls.add(ball);
    }
}

Answer 1

所以要分解你的代码:

当按下按钮时，您将执行以下代码:

Image ball = null;
new Layout().createEllipse(ball);
runnable = new Layout();
move = new Thread(runnable);
move.start();

这将创建一个新的布局。其中的 run() 方法将增加 X 和 Y 变量。它们在这里声明:

int X,Y;  //Coordenadas 

这些是实例变量，这意味着它们属于您新创建的布局。

然后你在新的 Layout 上调用 repaint()，这不会执行任何操作，因为这个新的 Layout 尚未添加到某个窗口。

那么，如何解决这个问题呢？

首先，您必须保留原始的布局:

class Animation extends JFrame { // no need to implement ActionListener
     Rectangle2D dimensions = new Rectangle2D.Double(0,0,850,595);  //Not implemented limits
     JButton animate, stop;
     Thread move;
     Layout layout;

然后在创建布局时记住布局:

// before: add(new Layout());
layout = new Layout();
add(layout);

然后使用 ActionListener 中的布局:

layout.createEllipse(ball);
move = new Thread(layout);
move.start();

这可能会出现一些并发问题(Swing 不是线程安全的)，因此为了更好地衡量，您应该在 AWTEventThread 中调用 repaint():

// in run(), was repaint():
EventQueue.invokeLater(new Runnable() {
   @Override
   public void run() {
       repaint();
   }
});

现在，还剩下一些清理任务:
删除此代码:

  @Override
public void actionPerformed(ActionEvent e) {} //Tag

不再需要它，因为您没有实现 ActionListener。

删除某些字段中的static修饰符，并添加 volatile :

volatile int X,Y;  //Coordenadas
volatile boolean running = true;  //"To interrupt the thread" momentaneously.
ArrayList<Image> balls = new ArrayList<>();  //Balls collection

从多个线程访问的变量需要

volatile 。

同时从 paint 方法中删除 repaint() 和 resetUI() 。你不需要它们。

对于paint中的图片:你应该缓存它们。将它们存储在一个字段中，这样您就不必每次都加载图片。

完成所有这些后，您的代码会更加干净，但仍然有一些问题需要解决。但至少你有一些工作。