按下按钮后如何在小程序（java）中添加图片？

Question

I have found an odd way of putting a picture in an applet just by itself, but it doesn't seem to work when i put the code in the buttonListener for the picture to show when a button is pressed. If you could also give me the simplest code for putting a picture in an applet, it would be very much appreciated!

the code that works:

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

public class gamedone extends JApplet {     
    public void init() {            
        Container cp = getContentPane();
        cp.setBackground(Color.black);
        Container content_pane = getContentPane();
        Image img = getImage(getCodeBase(), "portal-cake.jpg");
        DrawingPanel drawing_panel =  new DrawingPanel(img);
        // Add the DrawingPanel to the content pane.
        content_pane.add(drawing_panel);
      } // init
}
    class DrawingPanel extends JPanel
    {
      Image img;
      DrawingPanel (Image img)
      { this.img = img; }
    
      public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(img, 0, 0, this);
        }
    }

but when this is the program i added it to, and the button doesn't make it work:

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

public class TypeInNames extends JApplet{
     JButton StartButton;
     JTextField name1, name2;
     String player1, player2;
     String reply;
     
     Container cp = getContentPane();

     public void init() 
     {
        setSize(350, 400);
        setLayout(null);
        cp.setBackground(Color.black);
        StartButton = new JButton("Start Game!");
        name1 = new JTextField("Player 1",35);
        name2 = new JTextField("Player 2",35);
        //(x, y, width, height);
        StartButton.setBounds(115,200,120,30);
        name1.setBounds(115,140,120,20);
        name2.setBounds(115,170,120,20);
        startGame();
     }
     
     public void startGame()
     {
        add(StartButton);
        add(name1);
        add(name2);
        StartButton.addActionListener(new ButtonListener());
     }
     
     public void game()
     {
        
     }
     
     public void endGame()
     {
        Container cp = getContentPane();
        cp.setBackground(Color.black);
        Container content_pane = getContentPane();
        Image img = getImage(getCodeBase(), "portal-cake.jpg");
        DrawingPanel drawing_panel =  new DrawingPanel(img);
        // Add the DrawingPanel to the content pane.
        content_pane.add(drawing_panel);
     }
         
     private class ButtonListener implements ActionListener{
         public void actionPerformed(ActionEvent event)
         {
            if (event.getSource() == StartButton)
            {
                player1 = name1.getText();
                player2 = name2.getText();
                remove(StartButton);
                remove(name1);
                remove(name2);
                endGame();
                repaint();
            }
         }
     }
    }

Answer 1

Not sure about this but you could try the following:

1. You should call setBounds() on your drawing_panel

2. images load asynchronously; you may want to use an ImageObserver to know when it has loaded, then repaint . You could override your DrawingPanel.imageUpdate() method.

3. is the tree being updated? you may need to call getContentPane().invalidate() after adding the component.