Question

我不知道为什么在我的run方法中没有打印。我调用repaint并在horsethread类中覆盖它。这是我的代码。当我运行程序并点击Run Race时，它不会向面板绘制任何内容，任何想法？

import javax.swing.JFrame;



public class HorseTester {
  public static void main(String[] args) 
    {
        JFrame frame = new HorsePanel();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}


import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;
import javax.swing.JButton;

import java.awt.GridLayout;
import java.util.ArrayList;

public class HorsePanel extends JFrame
{
    private JPanel panel;
    private JButton reset;
    private JButton quit;
    private JButton run;
    private ActionListener listener;
    private static final int NUM_OF_HORSES = 5;
    public static final int FRAME_WIDTH = 400;
    public static final int FRAME_HEIGHT = 400;
    private ArrayList<Thread> allThreads = new ArrayList<Thread>();
    private ArrayList<HorseThread> horses = new ArrayList<HorseThread>();

    public HorsePanel() 
    {
        //Allocating the memory for horses
        for(int i=0;i<NUM_OF_HORSES;i++)
            horses.add(new HorseThread(i+1));

        //Adding them to thread pool
        for(int i=0;i<NUM_OF_HORSES;i++)
            allThreads.add( new Thread(horses.get(i)));

        createPanel();
        createRunRace();
        createQuit();
        setSize(FRAME_WIDTH, FRAME_HEIGHT);
    }






    public void createRunRace()
    {

        class RunRace implements ActionListener
        {
            public void actionPerformed(ActionEvent rightEvent)
            {
                run.setEnabled(false);
                for(int i=0;i<NUM_OF_HORSES;i++)
                    allThreads.get(i).start();

            }
        }

        ActionListener a = new RunRace();
        this.run.addActionListener(a);
    }

    public void createQuit()
    {           
        class QuitRace implements ActionListener
        {
            public void actionPerformed(ActionEvent rightEvent)
            {
                System.exit(0);             
            }
        }

        ActionListener b = new QuitRace();
        this.quit.addActionListener(b);
    }
    public void createPanel()
    {
        panel = new JPanel(new BorderLayout());
        JPanel drawingPanel = new JPanel();
        this.run = new JButton("Run Race");
        this.quit = new JButton("Quit");
        this.reset = new JButton("Reset");
        JPanel topPanel = new JPanel();


        topPanel.setLayout(new GridLayout(1, 3));
        topPanel.add(run);
        topPanel.add(reset);
        topPanel.add(quit);
        panel.add(topPanel, BorderLayout.NORTH);
        panel.add(drawingPanel, BorderLayout.SOUTH);

        add(panel);
    }
}



import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Line2D;
import javax.swing.JComponent;

public class HorseThread extends JComponent implements Runnable
{
public static final int X_START = 10;
public static final int Y_START = 20;

private Horse horse;
private int xpos, ypos;

public HorseThread(int offset) 
{
    xpos = X_START;
    ypos = Y_START * offset;
    horse = new Horse(xpos, ypos);
}

public void paintComponent(Graphics g) 
{
    Graphics2D g2 = (Graphics2D) g;
    horse.draw(g2);
}

/**
 * Run method that thread executes and makes horses go across
 * the screen racing.
 */
public void run() 
{
    repaint();
}
}


import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;

public class Horse 
{
private int xTop;
private int yTop;
public static final int RING_WIDTH = 20;

public Horse(int x, int y) 
{
    xTop = x;
    yTop = y;
}

public void setXY(int dx, int dy)
{
    xTop = dx;
    yTop = dy;
}

public void draw(Graphics2D g2) 
{
    Ellipse2D.Double horse = new Ellipse2D.Double(xTop, yTop, RING_WIDTH,   RING_WIDTH);
    g2.setColor(Color.BLUE);
    g2.fill(horse);
    g2.setColor(Color.WHITE);
    g2.fill(horse);     
}

}

Answer 1

主要问题是，HorseThread从JComponent延伸，但您实际上从未将其添加到任何内容中，因此它永远不会被绘制。

相反，如果您创建了TrackPane并在paintComponent方法中绘制了每匹马（HorseThread无需从{{1}延伸}），你可能会有更好的运气。

另请注意，一旦JComponent完成，就无法重新启动......

例如......

Horsing around

Thread

另请注意，Swing不是线程安全的，在此环境中使用import java.awt.BorderLayout; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.geom.Ellipse2D; import java.util.ArrayList; import javax.swing.JButton; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JPanel; public class HorseTester { public static void main(String[] args) { new HorseTester(); } public HorseTester() { JFrame frame = new HorsePanel(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } public class HorsePanel extends JFrame { private JPanel panel; private JButton reset; private JButton quit; private JButton run; private ActionListener listener; public static final int FRAME_WIDTH = 400; public static final int FRAME_HEIGHT = 400; private TrackPane trackPane; public HorsePanel() { createPanel(); createRunRace(); createQuit(); setSize(FRAME_WIDTH, FRAME_HEIGHT); } public void createRunRace() { class RunRace implements ActionListener { public void actionPerformed(ActionEvent rightEvent) { run.setEnabled(false); trackPane.start(); } } ActionListener a = new RunRace(); this.run.addActionListener(a); } public void createQuit() { class QuitRace implements ActionListener { public void actionPerformed(ActionEvent rightEvent) { System.exit(0); } } ActionListener b = new QuitRace(); this.quit.addActionListener(b); } public void createPanel() { panel = new JPanel(new BorderLayout()); trackPane = new TrackPane(); this.run = new JButton("Run Race"); this.quit = new JButton("Quit"); this.reset = new JButton("Reset"); JPanel topPanel = new JPanel(); topPanel.setLayout(new GridLayout(1, 3)); topPanel.add(run); topPanel.add(reset); topPanel.add(quit); panel.add(topPanel, BorderLayout.NORTH); panel.add(trackPane, BorderLayout.CENTER); add(panel); } } public class TrackPane extends JPanel { private static final int NUM_OF_HORSES = 5; private ArrayList<HorseThread> horses = new ArrayList<HorseThread>(); private ArrayList<Thread> threads = new ArrayList<Thread>(25); public TrackPane() { setBackground(Color.GREEN); reset(); } public void reset() { // Should dispose of any running threads... horses.clear(); //Allocating the memory for horses for (int i = 0; i < NUM_OF_HORSES; i++) { horses.add(new HorseThread(this, i + 1)); } } public void start() { // Should dispose of any running threads... threads.clear(); for (int i = 0; i < horses.size(); i++) { Thread thread = new Thread(horses.get(i)); thread.start(); threads.add(thread); } } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); for (HorseThread horse : horses) { horse.paint(g); } } } public class HorseThread implements Runnable { public static final int X_START = 10; public static final int Y_START = 20; private Horse horse; private int xpos, ypos; private TrackPane track; public HorseThread(TrackPane track, int offset) { xpos = X_START; ypos = Y_START * offset; horse = new Horse(xpos, ypos); this.track = track; } public void paint(Graphics g) { Graphics2D g2 = (Graphics2D) g; horse.draw(g2); } /** * Run method that thread executes and makes horses go across the screen * racing. */ public void run() { track.repaint(); } } public class Horse { private int xTop; private int yTop; public static final int RING_WIDTH = 20; public Horse(int x, int y) { xTop = x; yTop = y; } public void setXY(int dx, int dy) { xTop = dx; yTop = dy; } public void draw(Graphics2D g2) { Ellipse2D.Double horse = new Ellipse2D.Double(xTop, yTop, RING_WIDTH, RING_WIDTH); g2.setColor(Color.BLUE); g2.fill(horse); g2.setColor(Color.WHITE); g2.draw(horse); } } }时要小心;）

使用Java中的线程绘制到面板

1 个答案: