GUI Program Java - program do malowania

Question

Próbowałem dowiedzieć się, co jest nie tak z moim kodem tutaj. Chodzi o to, aby stworzyć mały program malarski i mieć czerwone, zielone, niebieskie i jasne przyciski. Mam wszystko, co mogę wymyślić, żeby zadziałało, ale nie mogę zrozumieć, co jest nie tak z kodem. Program otwiera się i natychmiast się zamyka.

import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 

public class Paint{ 

    public static void main(String[] args){ 
      gui g = new gui(); 
      g.setVisible(true); 

    } 

} 

public class gui extends JComponent implements ActionListener{ 
    JButton red, green, blue, clear; 
    Image image; 
    Graphics2D draw; 
    int x, y, prevX, prevY; 

    gui(){ 
      JFrame frame = new JFrame("Paint"); 
      Container content = frame.getContentPane(); 
      content.setLayout(new BorderLayout()); 
      setDoubleBuffered(false); 

      JPanel panel = new JPanel(); 
      content.add(panel, BorderLayout.SOUTH); 
      panel.setPreferredSize(new Dimension(32, 68)); 
      panel.setMinimumSize(new Dimension(32, 68)); 
      panel.setMaximumSize(new Dimension(32, 68)); 


      red = new JButton("Red"); 
      green = new JButton("Green"); 
      blue = new JButton("Blue"); 
      clear = new JButton("Clear"); 

      red.setPreferredSize(new Dimension(50, 16)); 
      green.setPreferredSize(new Dimension(50,16)); 
      blue.setPreferredSize(new Dimension(50, 16)); 

      panel.add(red); 
      panel.add(green); 
      panel.add(blue); 
      panel.add(clear); 

      red.addActionListener(this); 
      green.addActionListener(this); 
      blue.addActionListener(this); 
      clear.addActionListener(this); 

      frame.setSize(500, 500); 


      addMouseListener(new MouseAdapter(){ 
        public void mousePressed(MouseEvent e){ 
          prevX = e.getX(); 
          prevY = e.getY(); 
        } 

      }); 

      addMouseMotionListener(new MouseMotionAdapter(){ 
        public void mouseDragged(MouseEvent e){ 
          x = e.getX(); 
          y = e.getY(); 
          draw.drawLine(prevX, prevY, x, y); 
          repaint(); 
          prevX = x; 
          prevY = y; 

        } 


      }); 

    } 


    public void paintComponent(Graphics g){ 

      if(image==null){ 
        image = createImage(getSize().width, getSize().height); 

        draw = (Graphics2D)image.getGraphics(); 

        draw.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

        draw.setPaint(Color.white); 
        draw.fillRect(0, 0, getSize().width, getSize().height); 
        draw.setPaint(Color.black); 
        repaint(); 
      } 

      g.drawImage(image, 0, 0, null); 

    } 


    public void actionPerformed(ActionEvent e) { 
     if(e.getSource()==red){ 
      draw.setPaint(Color.red); 
      repaint(); 
     } 
     if(e.getSource()==green){ 
      draw.setPaint(Color.green); 
      repaint(); 
     } 
     if(e.getSource()==blue){ 
      draw.setPaint(Color.blue); 
      repaint(); 
     } 
     if(e.getSource()==clear){ 
      draw.setPaint(Color.white); 
      draw.fillRect(0, 0, getSize().width, getSize().height); 
      draw.setPaint(Color.black); 
      repaint(); 
     } 


    } 


} 

Answer 1

swój użyć właściwości widoczności z ramą i panelem, a także jak

frame.setVisible(true); 

linii g.setVisible(true); nie działa dla Ciebie, jak rozszerzyły swoją klasę JComponent i twój używasz ramkę i nie ustawienie jego właściwość, aby ustawić ją widoczną.

sam problem wystąpić maksymalnie z panelu tak swoje trzeba ustawić swoją własność, jak również I-e

panel.setVisible(true); 

Oto twój pełny kod, który działa po dodaniu tych właściwości

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Container; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.Image; 
import java.awt.RenderingHints; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.MouseAdapter; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseMotionAdapter; 

import javax.swing.JButton; 
import javax.swing.JComponent; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 

public class Paint{ 

    public static void main(String[] args){ 
      gui g = new gui(); 
      g.setVisible(true); 

    } 

} 

class gui extends JComponent implements ActionListener{ 
    JButton red, green, blue, clear; 
    Image image; 
    Graphics2D draw; 
    int x, y, prevX, prevY; 

    gui(){ 
      JFrame frame = new JFrame("Paint"); 
      Container content = frame.getContentPane(); 
      content.setLayout(new BorderLayout()); 
      setDoubleBuffered(false); 

      JPanel panel = new JPanel(); 
      content.add(panel, BorderLayout.SOUTH); 
      panel.setPreferredSize(new Dimension(32, 68)); 
      panel.setMinimumSize(new Dimension(32, 68)); 
      panel.setMaximumSize(new Dimension(32, 68)); 


      red = new JButton("Red"); 
      green = new JButton("Green"); 
      blue = new JButton("Blue"); 
      clear = new JButton("Clear"); 

      red.setPreferredSize(new Dimension(50, 16)); 
      green.setPreferredSize(new Dimension(50,16)); 
      blue.setPreferredSize(new Dimension(50, 16)); 

      panel.add(red); 
      panel.add(green); 
      panel.add(blue); 
      panel.add(clear); 

      panel.setVisible(true); 

      red.addActionListener(this); 
      green.addActionListener(this); 
      blue.addActionListener(this); 
      clear.addActionListener(this); 

      frame.setSize(500, 500); 

      frame.setVisible(true)   ; 


      addMouseListener(new MouseAdapter(){ 
        public void mousePressed(MouseEvent e){ 
          prevX = e.getX(); 
          prevY = e.getY(); 
        } 

      }); 

      addMouseMotionListener(new MouseMotionAdapter(){ 
        public void mouseDragged(MouseEvent e){ 
          x = e.getX(); 
          y = e.getY(); 
          draw.drawLine(prevX, prevY, x, y); 
          repaint(); 
          prevX = x; 
          prevY = y; 

        } 


      }); 

    } 


    public void paintComponent(Graphics g){ 

      if(image==null){ 
        image = createImage(getSize().width, getSize().height); 

        draw = (Graphics2D)image.getGraphics(); 

        draw.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); 

        draw.setPaint(Color.white); 
        draw.fillRect(0, 0, getSize().width, getSize().height); 
        draw.setPaint(Color.black); 
        repaint(); 
      } 

      g.drawImage(image, 0, 0, null); 

    } 


    public void actionPerformed(ActionEvent e) { 
     if(e.getSource()==red){ 
      draw.setPaint(Color.red); 
      repaint(); 
     } 
     if(e.getSource()==green){ 
      draw.setPaint(Color.green); 
      repaint(); 
     } 
     if(e.getSource()==blue){ 
      draw.setPaint(Color.blue); 
      repaint(); 
     } 
     if(e.getSource()==clear){ 
      draw.setPaint(Color.white); 
      draw.fillRect(0, 0, getSize().width, getSize().height); 
      draw.setPaint(Color.black); 
      repaint(); 
     } 


    } 


}