Java 图形中的paintComponent 问题

Question

我正在创建一个简单的游戏，涉及玩按钮。我的代码分为两个独立的程序，GraphicsMain 和 GraphicsPanel。总的来说，我已经构建了 Jframe 和按钮。在面板中，是我的图形。我的问题是尝试让 PaintComponent 和图形在我的主程序中工作。

我尝试将库和代码放入第一个程序（主程序）中，但它不起作用......

//Here is my main program:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Color;
public class GraphicsMain extends JFrame{
public static void main(String[] args){ 
    
    public void paintComponent(Graphics g){
        Graphics2D g2 = (Graphics2D) g;
    
    GraphicsMain window = new GraphicsMain();
    JPanel p = new JPanel();
    p.add(new GraphicsPanel());  //  add a class that extends JPanel
    window.setTitle("Arrays Project");
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setContentPane(p);
    window.pack();
    window.setLocationRelativeTo(null);
    window.setVisible(true);
    //Buttons for Players to select their move:
    JButton button = new JButton("Add 1:");
    button.setBounds(29, 400, 75, 50);
    JButton button2 = new JButton("Add 2:");
    button2.setBounds(101, 400, 75, 50);
    JButton button3 = new JButton("Add 1:");
    button3.setBounds(329, 400, 75, 50);
    JButton button4 = new JButton("Add 2:");
    button4.setBounds(401, 400, 75, 50);
    window.setLayout(null);
    //Adds buttons to the frame:
    window.add(button);
    window.add(button2);
    window.add(button3);
    window.add(button4);
    //Makes the frame visible:
    window.setVisible(true);
    //Action that occurs when the players click on their buttons:
    button.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            g2.fillOval(20, 20, 20, 20);
        }
    });
    button2.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            // Display a message dialog when the button is clicked
            JOptionPane.showMessageDialog(window, "Button Clicked!");
        }
    });
    button3.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            // Display a message dialog when the button is clicked
            JOptionPane.showMessageDialog(window, "Button Clicked!");
        }
    });
    button4.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            // Display a message dialog when the button is clicked
            JOptionPane.showMessageDialog(window, "Button Clicked!");
        }
    });
    }
    }
}

//Here is my panel program:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JPanel;
import java.awt.Font;

public class GraphicsPanel extends JPanel{

    public GraphicsPanel(){
        setPreferredSize(new Dimension(500, 500));
    }

    public void paintComponent(Graphics g){
        Graphics2D g2 = (Graphics2D) g;
        //1x10 board for the game:
        int count = 0;
        int [] board = new int [10];
        for (int i = 0; i < board.length; i++) { 
            g2.drawRect(0 + count, 250, 50, 50);
            count += 50;
        }
        //Labels for each square 1-10:
        g2.setFont(new Font("TimesRoman", Font.PLAIN, 20));
        g2.drawString("1", 20,  325);
        g2.drawString("2", 70,  325);
        g2.drawString("3", 120,  325);
        g2.drawString("4", 170,  325);
        g2.drawString("5", 220,  325);
        g2.drawString("6", 270,  325);
        g2.drawString("7", 320,  325);
        g2.drawString("8", 370,  325);
        g2.drawString("9", 420,  325);
        g2.drawString("10", 465,  325);
        //Title and instructions for players:
        g2.drawString("1, 2, …, 10 Game", 175,  25);
            g2.drawString("To Play: Players alternate placing either one or two pieces", 10,  60);
        g2.drawString("on the leftmost open squares. In this game, we don’t", 30,  85);
        g2.drawString("distinguish between players’ pieces, so we’ll call", 40, 110);
        g2.drawString("them left and right. Left will go first.", 85,  135);
        g2.drawString("The first player to place the tenth piece on the board wins!", 15, 170);
        //Labels for players buttons:
        g2.drawString("Player 1", 67,  385);
        g2.drawString("Player 2", 367,  385);   
    }
}

Answer 1

我建议您进行一些更改，首先声明一个静态 GraphicsPanel 对象，然后在 main 方法中实例化该对象，这需要能够调用我们在 GraphicsPanel 类中创建的 setDrawing 方法，以便启用相关画画。

在图形主中：

// delete public void paintComponent(Graphics g){
// delete Graphics2D g2 = (Graphics2D) g;
pan = new GraphicsPanel();
p.add( pan );  //  add a class that extends JPanel

button.addActionListener( new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        pan.setDrawing( true );
        pan.repaint();
    }
});

在图形面板中：

boolean drawing;

public void setDrawing( boolean draw ) {
   dibujar = draw;
}

在paintComponent中：

if( dibujar ) {
   g2.fillOval( 20, 20, 20, 20 );
}

所有代码：

public class GraphicsMain extends JFrame {

   static GraphicsPanel pan;

   public static void main( String[] args ) {
      GraphicsMain window = new GraphicsMain();
      JPanel p = new JPanel();
      pan = new GraphicsPanel();
      p.add( pan );  //  add a class that extends JPanel
      window.setTitle( "Arrays Project" );
      window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
      window.setContentPane( p );
      window.pack();
      window.setLocationRelativeTo( null );
      window.setVisible( true );
      //Buttons for Players to select their move:
      JButton button = new JButton( "Add 1:" );
      button.setBounds( 29, 400, 75, 50 );
      JButton button2 = new JButton( "Add 2:" );
      button2.setBounds( 101, 400, 75, 50 );
      JButton button3 = new JButton( "Add 1:" );
      button3.setBounds( 329, 400, 75, 50 );
      JButton button4 = new JButton( "Add 2:" );
      button4.setBounds( 401, 400, 75, 50 );
      window.setLayout( null );
      //Adds buttons to the frame:
      window.add( button );
      window.add( button2 );
      window.add( button3 );
      window.add( button4 );
      //Makes the frame visible:
      window.setVisible( true );
      //Action that occurs when the players click on their buttons:
      button.addActionListener( new ActionListener() {
         @Override
         public void actionPerformed( ActionEvent e ) {
            pan.setDrawing( true );
            pan.repaint();
         }
      } );
      button2.addActionListener( new ActionListener() {
         @Override
         public void actionPerformed( ActionEvent e ) {
            // Display a message dialog when the button is clicked
            JOptionPane.showMessageDialog( window, "Button Clicked!" );
         }
      } );
      button3.addActionListener( new ActionListener() {
         @Override
         public void actionPerformed( ActionEvent e ) {
            // Display a message dialog when the button is clicked
            JOptionPane.showMessageDialog( window, "Button Clicked!" );
         }
      } );
      button4.addActionListener( new ActionListener() {
         @Override
         public void actionPerformed( ActionEvent e ) {
            // Display a message dialog when the button is clicked
            JOptionPane.showMessageDialog( window, "Button Clicked!" );
         }
      } );
   }
}

public class GraphicsPanel extends JPanel {

   boolean drawing;
   
   public GraphicsPanel() {
      setPreferredSize( new Dimension( 500, 500 ) );
   }

   @Override
   public void paintComponent( Graphics g ) {
      Graphics2D g2 = ( Graphics2D ) g;
      //1x10 board for the game:
      int count = 0;
      int[] board = new int[ 10 ];
      for( int i = 0; i < board.length; i ++ ) {
         g2.drawRect( 0 + count, 250, 50, 50 );
         count += 50;
      }
      //Labels for each square 1-10:
      g2.setFont( new Font( "TimesRoman", Font.PLAIN, 20 ) );
      g2.drawString( "1", 20, 325 );
      g2.drawString( "2", 70, 325 );
      g2.drawString( "3", 120, 325 );
      g2.drawString( "4", 170, 325 );
      g2.drawString( "5", 220, 325 );
      g2.drawString( "6", 270, 325 );
      g2.drawString( "7", 320, 325 );
      g2.drawString( "8", 370, 325 );
      g2.drawString( "9", 420, 325 );
      g2.drawString( "10", 465, 325 );
      //Title and instructions for players:
      g2.drawString( "1, 2, …, 10 Game", 175, 25 );
      g2.drawString( "To Play: Players alternate placing either one or two pieces", 10, 60 );
      g2.drawString( "on the leftmost open squares. In this game, we don’t", 30, 85 );
      g2.drawString( "distinguish between players’ pieces, so we’ll call", 40, 110 );
      g2.drawString( "them left and right. Left will go first.", 85, 135 );
      g2.drawString( "The first player to place the tenth piece on the board wins!", 15, 170 );
      //Labels for players buttons:
      g2.drawString( "Player 1", 67, 385 );
      g2.drawString( "Player 2", 367, 385 );
      if( drawing ) {
         g2.fillOval( 20, 20, 20, 20 );
      }
   }
   
   public void setDrawing( boolean draw ) {
      drawing = draw;
   }
}